New CONFIG_NTYPES_VERSION file, use for SHRLIB_VERSION

Bump SHRLIB version
Add isCompatible reimplementation note to RELEASE_NOTES
2019-07-29 11:14:27 -05:00 · 2019-07-26 17:04:30 -04:00 · 2019-07-26 17:02:28 -04:00 · 2019-06-14 11:43:42 -04:00 · 2019-06-14 08:41:27 -04:00 · 2019-06-14 08:41:10 -04:00
41 changed files with 1058 additions and 1258 deletions
--- a/.ci/travis-build.sh
+++ b/.ci/travis-build.sh
@@ -1,21 +1,10 @@
 #!/bin/sh
 set -e -x

-# set RTEMS to eg. "4.9" or "4.10"
-# requires qemu, bison, flex, texinfo, install-info
-if [ -n "$RTEMS" ]
-then
-  # find local qemu-system-i386
-  export PATH="$HOME/.cache/qemu/usr/bin:$PATH"
-  echo -n "Using QEMU: "
-  type qemu-system-i386 || echo "Missing qemu"
-  EXTRA=RTEMS_QEMU_FIXUPS=YES
-fi
-
 make -j2 $EXTRA

 if [ "$TEST" != "NO" ]
 then
-  make tapfiles
-  make -s test-results
+  make -j2 tapfiles
+  make -j2 -s test-results
 fi
--- a/.ci/travis-prepare.sh
+++ b/.ci/travis-prepare.sh
@@ -3,35 +3,6 @@ set -e -x

 CURDIR="$PWD"

-QDIR="$HOME/.cache/qemu"
-
-if [ -n "$RTEMS" -a "$TEST" = "YES" ]
-then
-  git clone --quiet --branch vme --depth 10 https://github.com/mdavidsaver/qemu.git "$HOME/.build/qemu"
-  cd "$HOME/.build/qemu"
-
-  HEAD=`git log -n1 --pretty=format:%H`
-  echo "HEAD revision $HEAD"
-
-  [ -e "$HOME/.cache/qemu/built" ] && BUILT=`cat "$HOME/.cache/qemu/built"`
-  echo "Cached revision $BUILT"
-
-  if [ "$HEAD" != "$BUILT" ]
-  then
-    echo "Building QEMU"
-    git submodule --quiet update --init
-
-    install -d "$HOME/.build/qemu/build"
-    cd         "$HOME/.build/qemu/build"
-
-    "$HOME/.build/qemu/configure" --prefix="$HOME/.cache/qemu/usr" --target-list=i386-softmmu --disable-werror
-    make -j2
-    make install
-
-    echo "$HEAD" > "$HOME/.cache/qemu/built"
-  fi
-fi
-
 cat << EOF > $CURDIR/configure/RELEASE.local
 EPICS_BASE=$HOME/.source/epics-base
 EOF
@@ -39,24 +10,6 @@ EOF
 install -d "$HOME/.source"
 cd "$HOME/.source"

-add_base_module() {
-  MODULE=$1
-  BRANCH=$2
-  ( cd epics-base/modules && \
-  git clone --quiet --depth 5 --branch $MODULE/$BRANCH https://github.com/${REPOBASE:-epics-base}/epics-base.git $MODULE && \
-  cd $MODULE && git log -n1 )
-}
-
-add_gh_module() {
-  MODULE=$1
-  REPOOWNER=$2
-  REPONAME=$3
-  BRANCH=$4
-  ( cd epics-base/modules && \
-  git clone --quiet --depth 5 --branch $BRANCH https://github.com/$REPOOWNER/$REPONAME.git $MODULE && \
-  cd $MODULE && git log -n1 )
-}
-
 add_gh_flat() {
  MODULE=$1
  REPOOWNER=$2
@@ -71,17 +24,10 @@ ${MODULE_UC}=$HOME/.source/$MODULE
 EOF
 }

-if [ "$BRBASE" ]
-then
-  git clone --quiet --depth 5 --branch "$BRBASE" https://github.com/${REPOBASE:-epics-base}/epics-base.git epics-base
-  (cd epics-base && git log -n1 )
-  add_gh_flat pvData ${REPOPVD:-epics-base} pvDataCPP ${BRPVD:-master}
-else
-  git clone --quiet --depth 5 --branch core/"${BRCORE:-master}" https://github.com/${REPOBASE:-epics-base}/epics-base.git epics-base
-  ( cd epics-base && git log -n1 )
-  add_base_module libcom "${BRLIBCOM:-master}"
-  add_gh_module pvData ${REPOPVD:-epics-base} pvDataCPP ${BRPVD:-master}
-fi
+# not recursive
+git clone --quiet --depth 5 --branch "$BRBASE" https://github.com/${REPOBASE:-epics-base}/epics-base.git epics-base
+(cd epics-base && git log -n1 )
+add_gh_flat pvData ${REPOPVD:-epics-base} pvDataCPP ${BRPVD:-master}

 if [ -e $CURDIR/configure/RELEASE.local ]
 then
@@ -144,29 +90,18 @@ EOF
 if [ -n "$RTEMS" ]
 then
  echo "Cross RTEMS${RTEMS} for pc386"
-  install -d /home/travis/.cache
-  curl -L "https://github.com/mdavidsaver/rsb/releases/download/travis-20160306-2/rtems${RTEMS}-i386-trusty-20190306-2.tar.gz" \
-  | tar -C /home/travis/.cache -xj
+  curl -L "https://github.com/mdavidsaver/rsb/releases/download/20171203-${RTEMS}/i386-rtems${RTEMS}-trusty-20171203-${RTEMS}.tar.bz2" \
+  | tar -C / -xmj

  sed -i -e '/^RTEMS_VERSION/d' -e '/^RTEMS_BASE/d' epics-base/configure/os/CONFIG_SITE.Common.RTEMS
  cat << EOF >> epics-base/configure/os/CONFIG_SITE.Common.RTEMS
 RTEMS_VERSION=$RTEMS
-RTEMS_BASE=/home/travis/.cache/rtems${RTEMS}-i386
+RTEMS_BASE=$HOME/.rtems
 EOF
  cat << EOF >> epics-base/configure/CONFIG_SITE
-CROSS_COMPILER_TARGET_ARCHS+=RTEMS-pc386
+CROSS_COMPILER_TARGET_ARCHS += RTEMS-pc386-qemu
 EOF
-
-  # find local qemu-system-i386
-  export PATH="$HOME/.cache/qemu/usr/bin:$PATH"
-  echo -n "Using QEMU: "
-  type qemu-system-i386 || echo "Missing qemu"
-  EXTRA=RTEMS_QEMU_FIXUPS=YES
 fi

 make -j2 -C epics-base $EXTRA
-
-if [ "$BRBASE" ]
-then
-  make -j2 -C pvData $EXTRA
-fi
+make -j2 -C pvData $EXTRA
--- a/.travis.yml
+++ b/.travis.yml
@@ -11,19 +11,21 @@ addons:
    - perl
    - clang
    - g++-mingw-w64-i686
+    - qemu-system-x86
 install:
 - ./.ci/travis-prepare.sh
 script:
 - ./.ci/travis-build.sh
 env:
- - BRCORE=master BRLIBCOM=master BRPVD=master
- - CMPLR=clang
- - USR_CXXFLAGS=-std=c++11
- - CMPLR=clang USR_CXXFLAGS=-std=c++11
- - WINE=32 TEST=NO STATIC=YES
- - WINE=32 TEST=NO STATIC=NO
- - RTEMS=4.10 TEST=NO
- - RTEMS=4.9 TEST=NO
+ - BRBASE=7.0
+ - BRBASE=7.0 CMPLR=clang
+ - BRBASE=7.0 EXTRA="CMD_CXXFLAGS=-std=c++98"
+ - BRBASE=7.0 EXTRA="CMD_CXXFLAGS=-std=c++11"
+ - BRBASE=7.0 CMPLR=clang EXTRA="CMD_CXXFLAGS=-std=c++11"
+ - BRBASE=7.0 WINE=32 TEST=NO STATIC=YES
+ - BRBASE=7.0 WINE=32 TEST=NO STATIC=NO
+ - BRBASE=7.0 RTEMS=4.10 TEST=NO
+ - BRBASE=7.0 RTEMS=4.9 TEST=NO
 - BRBASE=3.16
 - BRBASE=3.15
 - BRBASE=3.14
--- a/README.md
+++ b/README.md
@@ -1,78 +1,17 @@
-normativeTypesCPP
-=================
+# normativeTypesCPP

-normativeTypesCPP is a C++ module containing helper classes which implement
-and provide support for the EPICS V4 Normative Types.
+The EPICS **Normative Types** are a set of standard high-level data types, designed to aid interoperability between EPICS PVA applications.

-The latter are a set of standard high-level data types to aid interoperability
-of EPICS V4 applications and are specified in the
-[NormativeTypes Specification](http://epics-pvdata.sourceforge.net/alpha/normativeTypes/normativeTypes.html).
+This normativeTypesCPP module is a part of the EPICS software toolkit that provides C++ helper classes which implement the EPICS Normative Types.

+## Links

-Status
------
+- General information about EPICS can be found at the
+  [EPICS Controls website](https://epics-controls.org).
+- API documentation for this module can be found in its
+  documentation directory, in particular the file
+  normativeTypesCPP.html

-The current release (5.0) implements fully the
-[16 Mar 2015 version](http://epics-pvdata.sourceforge.net/alpha/normativeTypes/normativeTypes_20150316.html)
-of the Normative Types Specification.
-
-The module status is alpha and the API and behaviour may change in future
-versions.
-
-The previous release (4.0) supported only 6 types. 
-There is no documentation yet for the new types added in 5.0.
-
-
-Further Info
------------
-
-Consult the documents in the documentation directory, in particular
-
-* normativeTypesCPP.html
-* RELEASE_NOTES.md
-
-Also see the [EPICS Version 4 website](http://epics-pvdata.sourceforge.net)
-
-
-Prerequisites
-------------
-
-normativeTypesCPP requires recent versions of the following software:
-
-1. EPICS Base (v3.14.12.3 or later)
-2. EPICS4 pvCommonCPP (4.1.0 or later)
-2. pvDataCPP (5.0.0 or later)
-
-(pvCommonCPP may not be needed depending on host/compiler.)
-
-
-Building
--------
-
-Building uses the make utility and the EPICS base build system.
-
-The build system needs the location of the prerequisites, e.g. by placing the
-lines of the form
-
-    PVDATA = /home/install/epicsV4/pvDataCPP
-    PVCOMMON = /home/install/epicsV4/pvCommonCPP
-    EPICS_BASE = /home/install/epics/base
-
-pointing to the locations in a file called RELEASE.local
-in the configure directory or the parent directory of normativeTypesCPP.
-
-With this in place, to build type make
-
-    make
-
-To perform a clean build type
-
-    make clean uninstall
-
-To run the unit tests type
-
-    make runtests
-
-For more information on the EPICS build system consult the
-[Application Development guide](http://www.aps.anl.gov/epics/base/R3-14/12-docs/AppDevGuide.pdf).
+## Building

+This module is included as a submodule of a full EPICS 7 release and will be compiled during builds of that software.
--- a/configure/CONFIG_NTYPES_VERSION
+++ b/configure/CONFIG_NTYPES_VERSION
@@ -0,0 +1,3 @@
+EPICS_NTYPES_MAJOR_VERSION = 6
+EPICS_NTYPES_MINOR_VERSION = 0
+EPICS_NTYPES_MAINTENANCE_VERSION = 0
--- a/configure/CONFIG_SITE
+++ b/configure/CONFIG_SITE
@@ -32,3 +32,5 @@ endif
 -include $(TOP)/../CONFIG_SITE.local
 -include $(TOP)/configure/CONFIG_SITE.local

+# MSVC - skip defining min()/max() macros
+USR_CPPFLAGS_WIN32 += -DNOMINMAX
--- a/configure/Makefile
+++ b/configure/Makefile
@@ -10,6 +10,8 @@ include $(TOP)/configure/CONFIG
 # but continue the build even if conflicts are found.
 CHECK_RELEASE = YES

+CFG += CONFIG_NTYPES_VERSION
+
 TARGETS = $(CONFIG_TARGETS)
 CONFIGS += $(subst ../,,$(wildcard $(CONFIG_INSTALLS)))

--- a/documentation/RELEASE_NOTES.html
+++ b/documentation/RELEASE_NOTES.html
@@ -1,147 +0,0 @@
-<?xml version="1.0" encoding="iso-8859-1"?>
-<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
-      "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
-<html xmlns="http://www.w3.org/1999/xhtml">
-
-<head>
-  <meta http-equiv="Content-Type" content="text/html;" />
-  <meta name="keywords" content="EPICS, EPICSv4" />
-  <title>EPICS V4 Normative Types Release Notes</title>
-  <link rel="stylesheet" type="text/css" href="../../base.css" />
-  <link rel="stylesheet" type="text/css" href="../../epicsv4.css" />
-
-</head>
-
-<body>
-
-<h1>Release 5.2.0</h1>
-
-<p>This release contains bug fixes and minor source updates needed to
-build against the latest version of pvData.</p>
-
-<h1>Release 5.1.2</h1>
-
-<p>The main changes since release 5.1.1 are:</p>
-
-<ul>
-<li>NTUnionBuilder: Add missing value() function</li>
-<li>Updated document: Now document all Normative Types</li>
-</ul>
-
-<h1>Release 5.1.1</h1>
-
-<p>The main changes since release 5.0 are:</p>
-
-<ul>
-<li>Linux shared library version added</li>
-<li>Headers and source locations have changed</li>
-<li>Missing is_a implementations added</li>
-<li>NTAttribute::addTags() is now non-virtual</li>
-<li>New license file replaces LICENSE and COPYRIGHT</li>
-</ul>
-
-<h2>Shared library version added</h2>
-
-<p>Linux shared library version numbers have been added by setting SHRLIB_VERSION
-(to 5.1 in this case). So shared object will be libnt.so.5.1 instead of
-libpvData.so.</p>
-
-<h2>Headers and source locations have changed</h2>
-
-<p>Source has moved out of nt directory directly into src.</p>
-
-<p>Headers have been moved into a pv directory. This facilitates using some IDEs
-such as Qt Creator.</p>
-
-<p>src/nt/ntscalar.cpp -> src/ntscalar.cpp
-src/nt/ntscalar.h   -> src/pv/ntscalar.h</p>
-
-<h2>Missing is_a implementations added</h2>
-
-<p>is_a(PVStructurePtr const &amp;) implementation has been added for each type.</p>
-
-<h1>Release 5.0</h1>
-
-<p>This release adds support through wrapper classes and builders for the
-remaining Normative Types:</p>
-
-<ul>
-<li>NTEnum</li>
-<li>NTMatrix</li>
-<li>NTURI</li>
-<li>NTAttribute</li>
-<li>NTContinuum</li>
-<li>NTHistogram</li>
-<li>NTAggregate</li>
-<li>NTUnion</li>
-<li>NTScalarMultiChannel</li>
-</ul>
-
-<p>Release 5.0 therefore implements fully the
-<a href="http://epics-pvdata.sourceforge.net/alpha/normativeTypes/normativeTypes_20150316.html">16 Mar 2015 version</a>
- of the normativeTypes specification.</p>
-
-<p>Each wrapper class has an extended API:</p>
-
-<ul>
-<li>is_a now has a convenience overload taking a PVStructure.</li>
-<li>isCompatible, reporting introspection type compatibility, now has an overload
-taking a Structure. The PVStructure version is retained as a convenience
-method and for backwards compatibility.</li>
-<li>An isValid function now reports validity of a compatible PVStructure's data
-with respect to the specification.</li>
-</ul>
-
-<p>Other changes are:</p>
-
-<ul>
-<li>Support for NTAttributes extended as required by NTNDArray
-(NTNDArrayAttributes).</li>
-<li>A new class for parsing NT IDs (NTID).</li>
-<li>Resolution of the confusion between column names and labels in NTTable and
-improved API. Function for adding columns is now addColumn rather than add.
-New getColumnNames function provided.</li>
-<li>isConnected is treated as an optional rather than a required field in
-NTMultiChannelArray. isConnected() and addIsConnected() functions added to
-wrapper and builder respectively.</li>
-<li>Unit tests for all new classes.</li>
-</ul>
-
-<h1>Release 4.0</h1>
-
-<p>This is the first release of normativeTypesCPP that is part of an official
-EPICS V4 release.
-It is a major rewrite of the previous versions of normativeTypesCPP.</p>
-
-<p>This release provides support through wrapper classes and builders for the
-following Normative Types:</p>
-
-<ul>
-<li>NTScalar</li>
-<li>NTScalarArray</li>
-<li>NTNameValue</li>
-<li>NTTable</li>
-<li>NTMultiChannel</li>
-<li>NTNDArray</li>
-</ul>
-
-<p>Each type has a wrapper class of the same name which has functions for checking 
-compatibility of existing PVStructures (isCompatible) and the reported types of 
-Structures (is_a), wraps existing PVStructures (wrap, wrapUnsafe) and provides
-a convenient interface to all required and optional fields.</p>
-
-<p>Each type has a builder which can create a Structure, a PVStructure or a
-wrapper around a new PVStructure. In each case optional or extra fields can be
-added and options such as choice of scalar type can be made.</p>
-
-<p>Additional features are:</p>
-
-<ul>
-<li>Utility classes NTField and NTPVField for standard structure fields and
-NTUtils for type IDs.</li>
-<li>Unit tests for the implemented classes.</li>
-</ul>
-
-
-</body>
-</html>
--- a/documentation/RELEASE_NOTES.md
+++ b/documentation/RELEASE_NOTES.md
@@ -1,11 +1,34 @@
-Release 5.2.0
-=============
+# normativeTypes Module
+
+This document summarizes the changes to the module between releases.
+
+## Release 6.0.0 (EPICS 7.0.3, July 2019)
+
+* Reimplement `isCompatible` methods to use a new internal validation API in order to make the implementation uniform, less repetitive and less strict.
+
+The new implementation is less strict in the sense that it considers types that can be converted into one another compatible with each other. For example, any `Scalar` is considered compatible with any other `Scalar`, regardless of the underlying type. Normative Types users are advised to use `getAs` and `putFrom` when getting/putting data from/into `PVScalar`s and `PVScalarArray`s.
+
+Also, `isCompatible` methods now disregard field order and extra fields that are not part of the specification.
+
+This change is not expected to break any current server or client, but it will break existing clients that rely on the previous `isCompatible` strictness once servers start to take advantage of `isCompatible` now being less strict.
+
+## Release 5.2.2
+
+- Fix NTTable::getColumnNames().
+
+## Release 5.2.1 (EPICS 7.0.2, Dec 2018)
+
+* No functional changes.
+* Removal of declaration for unimplemented PVNTField::createAlarmLimit() and elimination of unused variables.
+
+
+## Release 5.2.0 (EPICS 7.0.1, Dec 2017)

 This release contains bug fixes and minor source updates needed to
 build against the latest version of pvData.

-Release 5.1.2
-=============
+
+## Release 5.1.2 (EPICS V4.6, Aug 2016)

 The main changes since release 5.1.1 are:

@@ -13,8 +36,7 @@ The main changes since release 5.1.1 are:
 * Updated document: Now document all Normative Types


-Release 5.1.1
-=============
+## Release 5.1.1

 The main changes since release 5.0 are:

@@ -24,15 +46,13 @@ The main changes since release 5.0 are:
 * NTAttribute::addTags() is now non-virtual
 * New license file replaces LICENSE and COPYRIGHT

-Shared library version added
----------------------------
+### Shared library version added

 Linux shared library version numbers have been added by setting SHRLIB_VERSION
 (to 5.1 in this case). So shared object will be libnt.so.5.1 instead of
 libpvData.so.

-Headers and source locations have changed
-----------------------------------------
+### Headers and source locations have changed

 Source has moved out of nt directory directly into src.

@@ -42,14 +62,12 @@ such as Qt Creator.
 src/nt/ntscalar.cpp -> src/ntscalar.cpp
 src/nt/ntscalar.h   -> src/pv/ntscalar.h

-Missing is_a implementations added
----------------------------------
+### Missing is_a implementations added

 is_a(PVStructurePtr const &) implementation has been added for each type.


-Release 5.0
-===========
+## Release 5.0 (EPICS V4.5, Oct 2015)

 This release adds support through wrapper classes and builders for the
 remaining Normative Types:
@@ -90,8 +108,7 @@ Other changes are:
  wrapper and builder respectively.
 * Unit tests for all new classes.

-Release 4.0
-===========
+## Release 4.0 (EPICS V4.4, Dec 2014)

 This is the first release of normativeTypesCPP that is part of an official
 EPICS V4 release.
--- a/documentation/ntCPP.html
+++ b/documentation/ntCPP.html
@@ -4,7 +4,7 @@
 <html xmlns="http://www.w3.org/1999/xhtml">
 <head>
  <meta http-equiv="content-type" content="text/html; charset=iso-8859-1" />
-  <title>EPICS ntCPP</title>
+  <title>EPICS normativeTypesCPP</title>
  <link rel="stylesheet" type="text/css"
  href="http://epics-pvdata.sourceforge.net/base.css" />
  <link rel="stylesheet" type="text/css"
@@ -36,7 +36,7 @@
 <div class="head">
 <h1>EPICS normativeTypesCPP</h1>

-<h2 class="nocount">Release 5.2.0 - 2017.12.14</h2>
+<h2 class="nocount">Release 5.2.1 - December 2018</h2>
  <dl>
    <dt>Editors:</dt>
   <dd> Marty Kraimer<br />
--- a/jenkins/cloudbees_build
+++ b/jenkins/cloudbees_build
@@ -72,6 +72,6 @@ make distclean all
 make runtests

 ###########################################
-# Create distribution
+# Create cache

 tar --exclude=test* -czf normativeTypes.CB-dist.tar.gz lib include
--- a/jenkins/cloudbees_doc
+++ b/jenkins/cloudbees_doc
@@ -21,14 +21,7 @@ installE4 () {
    local module=$1
    local branch=$2

-    # If microbench version does not exist, try without
-    if [ "${MB}" = "WITH_MICROBENCH" ]; then
-        if wget -nv https://openepics.ci.cloudbees.com/job/e4-cpp-${module}-${branch}-build/BASE=${BASE},MB=WITH_MICROBENCH/lastSuccessfulBuild/artifact/${module}.CB-dist.tar.gz; then
-            wget -nv https://openepics.ci.cloudbees.com/job/e4-cpp-${module}-${branch}-build/BASE=${BASE},MB=NO_MICROBENCH/lastSuccessfulBuild/artifact/${module}.CB-dist.tar.gz
-        fi
-    else
-        wget -nv https://openepics.ci.cloudbees.com/job/e4-cpp-${module}-${branch}-build/BASE=${BASE},MB=NO_MICROBENCH/lastSuccessfulBuild/artifact/${module}.CB-dist.tar.gz
-    fi
+    wget -nv https://openepics.ci.cloudbees.com/job/e4-cpp-${module}-${branch}-build/BASE=${BASE}/lastSuccessfulBuild/artifact/${module}.CB-dist.tar.gz
    tar -xzf ${module}.CB-dist.tar.gz
 }

@@ -38,7 +31,6 @@ installE4 () {
 BASE=3.15.4
 PUBLISH=${PUBLISH:-NO}
 BRANCH=${BRANCH:-master}
-MB=NO_MICROBENCH

 ###########################################
 # Fetch and unpack dependencies
--- a/src/Makefile
+++ b/src/Makefile
@@ -47,7 +47,7 @@ LIBRARY = nt
 nt_LIBS += pvData Com

 # shared library ABI version.
-SHRLIB_VERSION ?= 5.2
+SHRLIB_VERSION ?= $(EPICS_NTYPES_MAJOR_VERSION).$(EPICS_NTYPES_MINOR_VERSION).$(EPICS_NTYPES_MAINTENANCE_VERSION)

 include $(TOP)/configure/RULES

--- a/src/ntaggregate.cpp
+++ b/src/ntaggregate.cpp
@@ -4,6 +4,8 @@
 * found in the file LICENSE that is included with the distribution
 */

+#include "validator.h"
+
 #define epicsExportSharedSymbols
 #include <pv/ntaggregate.h>
 #include <pv/ntutils.h>
@@ -194,83 +196,26 @@ bool NTAggregate::is_a(PVStructurePtr const & pvStructure)

 bool NTAggregate::isCompatible(StructureConstPtr const &structure)
 {
-    if (structure.get() == 0) return false;
-
-    ScalarConstPtr valueField = structure->getField<Scalar>("value");
-    if (valueField.get() == 0 || valueField->getScalarType() != pvDouble)
+    if (!structure)
        return false;

-    ScalarConstPtr nField = structure->getField<Scalar>("N");
-    if (nField.get() == 0 || nField->getScalarType() != pvLong)
-        return false;
+    Result result(structure);

-    FieldConstPtr field = structure->getField("dispersion");
-    if (field.get())
-    {
-        ScalarConstPtr dispersionField = structure->getField<Scalar>("dispersion");
-        if (!dispersionField.get() || dispersionField->getScalarType() != pvDouble)
-            return false;
-    }
-
-    field = structure->getField("first");
-    if (field.get())
-    {
-        ScalarConstPtr firstField = structure->getField<Scalar>("first");
-        if (!firstField.get() || firstField->getScalarType() != pvDouble)
-            return false;
-    }
-
-    field = structure->getField("firstTimeStamp");
-    if (field.get() && !ntField->isTimeStamp(field))
-        return false;
-
-    field = structure->getField("last");
-    if (field.get())
-    {
-        ScalarConstPtr lastField = structure->getField<Scalar>("last");
-        if (!lastField.get() || lastField->getScalarType() != pvDouble)
-            return false;
-    }
-
-    field = structure->getField("lastTimeStamp");
-    if (field.get() && !ntField->isTimeStamp(field))
-        return false;
-
-    field = structure->getField("max");
-    if (field.get())
-    {
-        ScalarConstPtr maxField = structure->getField<Scalar>("max");
-        if (!maxField.get() || maxField->getScalarType() != pvDouble)
-            return false;
-    }
-
-    field = structure->getField("min");
-    if (field.get())
-    {
-        ScalarConstPtr minField = structure->getField<Scalar>("min");
-        if (!minField.get() || minField->getScalarType() != pvDouble)
-            return false;
-    }
-
-    field = structure->getField("descriptor");
-    if (field.get())
-    {
-        ScalarConstPtr descriptorField = structure->getField<Scalar>("descriptor");
-        if (!descriptorField.get() || descriptorField->getScalarType() != pvString)
-            return false;
-    }
-
-    NTFieldPtr ntField = NTField::get();
-
-    field = structure->getField("alarm");
-    if (field.get() && !ntField->isAlarm(field))
-        return false;
-
-    field = structure->getField("timeStamp");
-    if (field.get() && !ntField->isTimeStamp(field))
-        return false;
-
-    return true;
+    return result
+        .is<Structure>()
+        .has<Scalar>("value")
+        .has<Scalar>("N")
+        .maybeHas<Scalar>("dispersion")
+        .maybeHas<Scalar>("first")
+        .maybeHas<&NTField::isTimeStamp, Structure>("firstTimeStamp")
+        .maybeHas<Scalar>("last")
+        .maybeHas<&NTField::isTimeStamp, Structure>("lastTimeStamp")
+        .maybeHas<Scalar>("max")
+        .maybeHas<Scalar>("min")
+        .maybeHas<Scalar>("descriptor")
+        .maybeHas<&NTField::isAlarm, Structure>("alarm")
+        .maybeHas<&NTField::isTimeStamp, Structure>("timeStamp")
+        .valid();
 }

 bool NTAggregate::isCompatible(PVStructurePtr const & pvStructure)
--- a/src/ntattribute.cpp
+++ b/src/ntattribute.cpp
@@ -4,6 +4,8 @@
 * found in the file LICENSE that is included with the distribution
 */

+#include "validator.h"
+
 #define epicsExportSharedSymbols
 #include <pv/ntattribute.h>
 #include <pv/ntutils.h>
@@ -130,46 +132,22 @@ bool NTAttribute::is_a(PVStructurePtr const & pvStructure)

 bool NTAttribute::isCompatible(StructureConstPtr const & structure)
 {
-    if (structure.get() == 0) return false;
-
-    ScalarConstPtr nameField = structure->getField<Scalar>("name");
-    if (nameField.get() == 0 || nameField->getScalarType() != pvString)
+    if (!structure)
        return false;

-    UnionConstPtr valueField = structure->getField<Union>("value");
-    if (valueField.get() == 0 || !valueField->isVariant())
-        return false;
+    Result result(structure);

-    FieldConstPtr field = structure->getField("tags");
-    if (field.get())
-    {
-        ScalarArrayConstPtr tagsField = structure->getField<ScalarArray>("tags");
-        if (tagsField.get() == 0 || tagsField->getElementType() != pvString)
-            return false;
-    }
-
-    field = structure->getField("descriptor");
-    if (field.get())
-    {
-        ScalarConstPtr descriptorField = structure->getField<Scalar>("descriptor");
-        if (!descriptorField.get() || descriptorField->getScalarType() != pvString)
-            return false;
-    }
-
-    NTFieldPtr ntField = NTField::get();
-
-    field = structure->getField("alarm");
-    if (field.get() && !ntField->isAlarm(field))
-        return false;
-
-    field = structure->getField("timeStamp");
-    if (field.get() && !ntField->isTimeStamp(field))
-        return false;
-
-    return true;
+    return result
+       .is<Structure>()
+       .has<Scalar>("name")
+       .has<Union>("value")
+       .maybeHas<ScalarArray>("tags")
+       .maybeHas<Scalar>("descriptor")
+       .maybeHas<&NTField::isAlarm, Structure>("alarm")
+       .maybeHas<&NTField::isTimeStamp, Structure>("timeStamp")
+       .valid();
 }

-
 bool NTAttribute::isCompatible(PVStructurePtr const & pvStructure)
 {
    if(!pvStructure) return false;
--- a/src/ntcontinuum.cpp
+++ b/src/ntcontinuum.cpp
@@ -4,6 +4,8 @@
 * found in the file LICENSE that is included with the distribution
 */

+#include "validator.h"
+
 #define epicsExportSharedSymbols
 #include <pv/ntcontinuum.h>
 #include <pv/ntutils.h>
@@ -122,42 +124,22 @@ bool NTContinuum::is_a(PVStructurePtr const & pvStructure)

 bool NTContinuum::isCompatible(StructureConstPtr const & structure)
 {
-    if (structure.get() == 0) return false;
-
-    ScalarArrayConstPtr baseField = structure->getField<ScalarArray>("base");
-    if (baseField.get() == 0 || baseField->getElementType() != pvDouble)
+    if (!structure)
        return false;

-    ScalarArrayConstPtr valueField = structure->getField<ScalarArray>("value");
-    if (valueField.get() == 0 || valueField->getElementType() != pvDouble)
-        return false;
+    Result result(structure);

-    ScalarArrayConstPtr unitsField = structure->getField<ScalarArray>("units");
-    if (unitsField.get() == 0 || unitsField->getElementType() != pvString)
-        return false;
-
-    FieldConstPtr field = structure->getField("descriptor");
-    if (field.get())
-    {
-        ScalarConstPtr descriptorField = structure->getField<Scalar>("descriptor");
-        if (!descriptorField.get() || descriptorField->getScalarType() != pvString)
-            return false;
-    }
-
-    NTFieldPtr ntField = NTField::get();
-
-    field = structure->getField("alarm");
-    if (field.get() && !ntField->isAlarm(field))
-        return false;
-
-    field = structure->getField("timeStamp");
-    if (field.get() && !ntField->isTimeStamp(field))
-        return false;
-
-    return true;
+    return result
+        .is<Structure>()
+        .has<ScalarArray>("base")
+        .has<ScalarArray>("value")
+        .has<ScalarArray>("units")
+        .maybeHas<Scalar>("descriptor")
+        .maybeHas<&NTField::isAlarm, Structure>("alarm")
+        .maybeHas<&NTField::isTimeStamp, Structure>("timeStamp")
+        .valid();
 }

-
 bool NTContinuum::isCompatible(PVStructurePtr const & pvStructure)
 {
    if(!pvStructure) return false;
--- a/src/ntenum.cpp
+++ b/src/ntenum.cpp
@@ -4,6 +4,8 @@
 * found in the file LICENSE that is included with the distribution
 */

+#include "validator.h"
+
 #define epicsExportSharedSymbols
 #include <pv/ntenum.h>
 #include <pv/ntutils.h>
@@ -121,34 +123,20 @@ bool NTEnum::is_a(PVStructurePtr const & pvStructure)

 bool NTEnum::isCompatible(StructureConstPtr const &structure)
 {
-    if (structure.get() == 0) return false;
-
-    NTFieldPtr ntField = NTField::get();
-
-    FieldConstPtr valueField = structure->getField("value");
-    if (!valueField.get() || !ntField->isEnumerated(valueField))
+    if (!structure)
        return false;

-    FieldConstPtr field = structure->getField("descriptor");
-    if (field.get())
-    {
-        ScalarConstPtr descriptorField = structure->getField<Scalar>("descriptor");
-        if (!descriptorField.get() || descriptorField->getScalarType() != pvString)
-            return false;
-    }
+    Result result(structure);

-    field = structure->getField("alarm");
-    if (field.get() && !ntField->isAlarm(field))
-        return false;
-
-    field = structure->getField("timeStamp");
-    if (field.get() && !ntField->isTimeStamp(field))
-        return false;
-
-    return true;
+    return result
+        .is<Structure>()
+        .has<&NTField::isEnumerated, Structure>("value")
+        .maybeHas<Scalar>("descriptor")
+        .maybeHas<&NTField::isAlarm, Structure>("alarm")
+        .maybeHas<&NTField::isTimeStamp, Structure>("timeStamp")
+        .valid();
 }

-
 bool NTEnum::isCompatible(PVStructurePtr const & pvStructure)
 {
    if(!pvStructure) return false;
--- a/src/ntfield.cpp
+++ b/src/ntfield.cpp
@@ -5,6 +5,7 @@
 */

 #include <pv/lock.h>
+#include "validator.h"

 #define epicsExportSharedSymbols
 #include <pv/ntfield.h>
@@ -31,198 +32,97 @@ NTField::NTField()
 {
 }

+Result& NTField::isEnumerated(Result& result)
+{
+    return result
+        .has<Scalar>("index")
+        .has<ScalarArray>("choices");
+}
+
 bool NTField::isEnumerated(FieldConstPtr const & field)
 {
-   if(field->getType()!=structure) return false;
-   StructureConstPtr structurePtr = static_pointer_cast<const Structure>(field);
-   FieldConstPtrArray fields = structurePtr->getFields();
-   StringArray names = structurePtr->getFieldNames();
-   size_t n = structurePtr->getNumberFields();
-   if(n!=2) return false;
-   FieldConstPtr f = fields[0];
-   if(names[0].compare("index")!=0) return false;
-   if(f->getType()!=scalar) return false;
-   ScalarConstPtr s = static_pointer_cast<const Scalar>(f);
-   if(s->getScalarType()!=pvInt) return false;
-   f = fields[1];
-   if(names[1].compare("choices")!=0) return false;
-   if(f->getType()!=scalarArray) return false;
-   ScalarConstPtr sa = static_pointer_cast<const Scalar>(f);
-   if(sa->getScalarType()!=pvString) return false;
-   return true;
+    Result result(field);
+    return isEnumerated(result.is<Structure>()).valid();
+}
+
+Result& NTField::isTimeStamp(Result& result)
+{
+    return result
+        .has<Scalar>("secondsPastEpoch")
+        .has<Scalar>("nanoseconds")
+        .has<Scalar>("userTag");
 }

 bool NTField::isTimeStamp(FieldConstPtr const & field)
 {
-   if(field->getType()!=structure) return false;
-   StructureConstPtr structurePtr = static_pointer_cast<const Structure>(field);
-   FieldConstPtrArray fields = structurePtr->getFields();
-   StringArray names = structurePtr->getFieldNames();
-   size_t  n = structurePtr->getNumberFields();
-   if(n!=3) return false;
-   FieldConstPtr f = fields[0];
-   if(names[0].compare("secondsPastEpoch")!=0) return false;
-   if(f->getType()!=scalar) return false;
-   ScalarConstPtr s = static_pointer_cast<const Scalar>(f);
-   if(s->getScalarType()!=pvLong) return false;
-   f = fields[1];
-   if(names[1].compare("nanoseconds")!=0) return false;
-   if(f->getType()!=scalar) return false;
-   s = static_pointer_cast<const Scalar>(f);
-   if(s->getScalarType()!=pvInt) return false;
-   f = fields[2];
-   if(names[2].compare("userTag")!=0) return false;
-   if(f->getType()!=scalar) return false;
-   s = static_pointer_cast<const Scalar>(f);
-   if(s->getScalarType()!=pvInt) return false;
-   return true;
+    Result result(field);
+    return isTimeStamp(result.is<Structure>()).valid();
+}
+
+Result& NTField::isAlarm(Result& result)
+{
+    return result
+        .has<Scalar>("severity")
+        .has<Scalar>("status")
+        .has<Scalar>("message");
 }

 bool NTField::isAlarm(FieldConstPtr const & field)
 {
-   if(field->getType()!=structure) return false;
-   StructureConstPtr structurePtr = static_pointer_cast<const Structure>(field);
-   FieldConstPtrArray fields = structurePtr->getFields();
-   StringArray names = structurePtr->getFieldNames();
-   size_t n = structurePtr->getNumberFields();
-   if(n!=3) return false;
-   FieldConstPtr f = fields[0];
-   if(names[0].compare("severity")!=0) return false;
-   if(f->getType()!=scalar) return false;
-   ScalarConstPtr s = static_pointer_cast<const Scalar>(f);
-   if(s->getScalarType()!=pvInt) return false;
-   f = fields[1];
-   if(names[1].compare("status")!=0) return false;
-   if(f->getType()!=scalar) return false;
-   s = static_pointer_cast<const Scalar>(f);
-   if(s->getScalarType()!=pvInt) return false;
-   f = fields[2];
-   if(names[2].compare("message")!=0) return false;
-   if(f->getType()!=scalar) return false;
-   s = static_pointer_cast<const Scalar>(f);
-   if(s->getScalarType()!=pvString) return false;
-   return true;
+    Result result(field);
+    return isAlarm(result.is<Structure>()).valid();
+}
+
+Result& NTField::isDisplay(Result& result)
+{
+    return result
+        .has<Scalar>("limitLow")
+        .has<Scalar>("limitHigh")
+        .has<Scalar>("description")
+        .has<Scalar>("format")
+        .has<Scalar>("units");
+
 }

 bool NTField::isDisplay(FieldConstPtr const & field)
 {
-   if(field->getType()!=structure) return false;
-   StructureConstPtr structurePtr = static_pointer_cast<const Structure>(field);
-   FieldConstPtrArray fields = structurePtr->getFields();
-   StringArray names = structurePtr->getFieldNames();
-   size_t n = structurePtr->getNumberFields();
-   if(n!=5) return false;
-   FieldConstPtr f = fields[0];
-   if(names[0].compare("limitLow")!=0) return false;
-   if(f->getType()!=scalar) return false;
-   ScalarConstPtr s = static_pointer_cast<const Scalar>(f);
-   if(s->getScalarType()!=pvDouble) return false;
-   f = fields[1];
-   if(names[1].compare("limitHigh")!=0) return false;
-   if(f->getType()!=scalar) return false;
-   s = static_pointer_cast<const Scalar>(f);
-   if(s->getScalarType()!=pvDouble) return false;
-   f = fields[2];
-   if(names[2].compare("description")!=0) return false;
-   if(f->getType()!=scalar) return false;
-   s = static_pointer_cast<const Scalar>(f);
-   if(s->getScalarType()!=pvString) return false;
-   f = fields[3];
-   if(names[3].compare("format")!=0) return false;
-   if(f->getType()!=scalar) return false;
-   s = static_pointer_cast<const Scalar>(f);
-   if(s->getScalarType()!=pvString) return false;
-   f = fields[4];
-   if(names[4].compare("units")!=0) return false;
-   if(f->getType()!=scalar) return false;
-   s = static_pointer_cast<const Scalar>(f);
-   if(s->getScalarType()!=pvString) return false;
-   return true;
+    Result result(field);
+    return isDisplay(result.is<Structure>()).valid();
+}
+
+Result& NTField::isAlarmLimit(Result& result)
+{
+    return result
+        .has<Scalar>("active")
+        .has<Scalar>("lowAlarmLimit")
+        .has<Scalar>("lowWarningLimit")
+        .has<Scalar>("highWarningLimit")
+        .has<Scalar>("highAlarmLimit")
+        .has<Scalar>("lowAlarmSeverity")
+        .has<Scalar>("lowWarningSeverity")
+        .has<Scalar>("highWarningSeverity")
+        .has<Scalar>("highAlarmSeverity")
+        .has<Scalar>("hysteresis");
 }

 bool NTField::isAlarmLimit(FieldConstPtr const & field)
 {
-   if(field->getType()!=structure) return false;
-   StructureConstPtr structurePtr = static_pointer_cast<const Structure>(field);
-   FieldConstPtrArray fields = structurePtr->getFields();
-   StringArray names = structurePtr->getFieldNames();
-   size_t n = structurePtr->getNumberFields();
-   if(n!=10) return false;
-   FieldConstPtr f = fields[0];
-   if(names[0].compare("active")!=0) return false;
-   if(f->getType()!=scalar) return false;
-   ScalarConstPtr s = static_pointer_cast<const Scalar>(f);
-   if(s->getScalarType()!=pvBoolean) return false;
-   f = fields[1];
-   if(names[1].compare("lowAlarmLimit")!=0) return false;
-   if(f->getType()!=scalar) return false;
-   s = static_pointer_cast<const Scalar>(f);
-   if(s->getScalarType()!=pvDouble) return false;
-   f = fields[2];
-   if(names[2].compare("lowWarningLimit")!=0) return false;
-   if(f->getType()!=scalar) return false;
-   s = static_pointer_cast<const Scalar>(f);
-   if(s->getScalarType()!=pvDouble) return false;
-   f = fields[3];
-   if(names[3].compare("highWarningLimit")!=0) return false;
-   if(f->getType()!=scalar) return false;
-   s = static_pointer_cast<const Scalar>(f);
-   if(s->getScalarType()!=pvDouble) return false;
-   f = fields[4];
-   if(names[4].compare("highAlarmLimit")!=0) return false;
-   if(f->getType()!=scalar) return false;
-   s = static_pointer_cast<const Scalar>(f);
-   if(s->getScalarType()!=pvDouble) return false;
-   f = fields[5];
-   if(names[5].compare("lowAlarmSeverity")!=0) return false;
-   if(f->getType()!=scalar) return false;
-   s = static_pointer_cast<const Scalar>(f);
-   if(s->getScalarType()!=pvInt) return false;
-   f = fields[6];
-   if(names[6].compare("lowWarningSeverity")!=0) return false;
-   if(f->getType()!=scalar) return false;
-   s = static_pointer_cast<const Scalar>(f);
-   if(s->getScalarType()!=pvInt) return false;
-   f = fields[7];
-   if(names[7].compare("highWarningSeverity")!=0) return false;
-   if(f->getType()!=scalar) return false;
-   s = static_pointer_cast<const Scalar>(f);
-   if(s->getScalarType()!=pvInt) return false;
-   f = fields[8];
-   if(names[8].compare("highAlarmSeverity")!=0) return false;
-   if(f->getType()!=scalar) return false;
-   s = static_pointer_cast<const Scalar>(f);
-   if(s->getScalarType()!=pvInt) return false;
-   f = fields[9];
-   if(names[9].compare("hysteresis")!=0) return false;
-   if(f->getType()!=scalar) return false;
-   return true;
+    Result result(field);
+    return isAlarmLimit(result.is<Structure>()).valid();
+}
+
+Result& NTField::isControl(Result& result)
+{
+    return result
+        .has<Scalar>("limitLow")
+        .has<Scalar>("limitHigh")
+        .has<Scalar>("minStep");
 }

 bool NTField::isControl(FieldConstPtr const & field)
 {
-   if(field->getType()!=structure) return false;
-   StructureConstPtr structurePtr = static_pointer_cast<const Structure>(field);
-   FieldConstPtrArray fields = structurePtr->getFields();
-   StringArray names = structurePtr->getFieldNames();
-   size_t n = structurePtr->getNumberFields();
-   if(n!=3) return false;
-   FieldConstPtr f = fields[0];
-   if(names[0].compare("limitLow")!=0) return false;
-   if(f->getType()!=scalar) return false;
-   ScalarConstPtr s = static_pointer_cast<const Scalar>(f);
-   if(s->getScalarType()!=pvDouble) return false;
-   f = fields[1];
-   if(names[1].compare("limitHigh")!=0) return false;
-   if(f->getType()!=scalar) return false;
-   s = static_pointer_cast<const Scalar>(f);
-   if(s->getScalarType()!=pvDouble) return false;
-   f = fields[2];
-   if(names[2].compare("minStep")!=0) return false;
-   if(f->getType()!=scalar) return false;
-   s = static_pointer_cast<const Scalar>(f);
-   if(s->getScalarType()!=pvDouble) return false;
-   return true;
+    Result result(field);
+    return isControl(result.is<Structure>()).valid();
 }

 StructureConstPtr NTField::createEnumerated()
--- a/src/nthistogram.cpp
+++ b/src/nthistogram.cpp
@@ -4,6 +4,8 @@
 * found in the file LICENSE that is included with the distribution
 */

+#include "validator.h"
+
 #define epicsExportSharedSymbols
 #include <pv/nthistogram.h>
 #include <pv/ntutils.h>
@@ -135,37 +137,19 @@ bool NTHistogram::is_a(PVStructurePtr const & pvStructure)

 bool NTHistogram::isCompatible(StructureConstPtr const &structure)
 {
-    if(!structure.get()) return false;
-
-    ScalarArrayConstPtr rangesField = structure->getField<ScalarArray>("ranges");
-    if(!rangesField.get() || rangesField->getElementType() != pvDouble) return false;
-
-    ScalarArrayConstPtr valueField = structure->getField<ScalarArray>("value");
-    if(!valueField.get()) return false;
-
-    ScalarType scalarType = valueField->getElementType();
-    if (scalarType != pvShort &&
-        scalarType != pvInt &&
-        scalarType != pvLong)
+    if (!structure)
        return false;

-    FieldConstPtr field = structure->getField("descriptor");
-    if(field)
-    {
-       ScalarConstPtr descriptorField = structure->getField<Scalar>("descriptor");
-       if (!descriptorField.get() || descriptorField->getScalarType() != pvString)
-           return false;
-    }
+    Result result(structure);

-    field = structure->getField("alarm");
-    if (field.get() && !ntField->isAlarm(field))
-        return false;
-
-    field = structure->getField("timeStamp");
-    if (field.get() && !ntField->isTimeStamp(field))
-        return false;
-
-    return true;
+    return result
+        .is<Structure>()
+        .has<ScalarArray>("ranges")
+        .has<ScalarArray>("value")
+        .maybeHas<Scalar>("descriptor")
+        .maybeHas<&NTField::isAlarm, Structure>("alarm")
+        .maybeHas<&NTField::isTimeStamp, Structure>("timeStamp")
+        .valid();
 }

 bool NTHistogram::isCompatible(PVStructurePtr const & pvStructure)
--- a/src/ntmatrix.cpp
+++ b/src/ntmatrix.cpp
@@ -4,6 +4,8 @@
 * found in the file LICENSE that is included with the distribution
 */

+#include "validator.h"
+
 #define epicsExportSharedSymbols
 #include <pv/ntmatrix.h>
 #include <pv/ntutils.h>
@@ -139,43 +141,20 @@ bool NTMatrix::is_a(PVStructurePtr const & pvStructure)

 bool NTMatrix::isCompatible(StructureConstPtr const & structure)
 {
-    if (structure.get() == 0) return false;
-
-    ScalarArrayConstPtr valueField = structure->getField<ScalarArray>("value");
-    if (valueField.get() == 0 || valueField->getElementType() != pvDouble)
+    if (!structure)
        return false;

-    FieldConstPtr field = structure->getField("dim");
-    if (field.get())
-    {
-        ScalarArrayConstPtr dimField = structure->getField<ScalarArray>("dim");
-        if (dimField.get() == 0 || dimField->getElementType() != pvInt)
-            return false;
-    }
+    Result result(structure);

-    field = structure->getField("descriptor");
-    if (field.get())
-    {
-        ScalarConstPtr descriptorField = structure->getField<Scalar>("descriptor");
-        if (!descriptorField.get() || descriptorField->getScalarType() != pvString)
-            return false;
-    }
-
-    NTFieldPtr ntField = NTField::get();
-
-    field = structure->getField("alarm");
-    if (field.get() && !ntField->isAlarm(field))
-        return false;
-
-    field = structure->getField("timeStamp");
-    if (field.get() && !ntField->isTimeStamp(field))
-        return false;
-
-    field = structure->getField("display");
-    if (field.get() && !ntField->isDisplay(field))
-        return false;
-
-    return true;
+    return result
+        .is<Structure>()
+        .has<ScalarArray>("value")
+        .maybeHas<ScalarArray>("dim")
+        .maybeHas<Scalar>("descriptor")
+        .maybeHas<&NTField::isAlarm, Structure>("alarm")
+        .maybeHas<&NTField::isTimeStamp, Structure>("timeStamp")
+        .maybeHas<&NTField::isDisplay, Structure>("display")
+        .valid();
 }

 bool NTMatrix::isCompatible(PVStructurePtr const & pvStructure)
--- a/src/ntmultiChannel.cpp
+++ b/src/ntmultiChannel.cpp
@@ -6,6 +6,8 @@

 #include <algorithm>

+#include "validator.h"
+
 #define epicsExportSharedSymbols
 #include <pv/ntmultiChannel.h>
 #include <pv/ntutils.h>
@@ -232,86 +234,27 @@ bool NTMultiChannel::is_a(PVStructurePtr const & pvStructure)

 bool NTMultiChannel::isCompatible(StructureConstPtr const & structure)
 {
-    if (!structure.get()) return false;
-
-    UnionArrayConstPtr valueField = structure->getField<UnionArray>("value");
-    if (!valueField.get()) return false;
-
-    ScalarArrayConstPtr channelNameField = structure->getField<ScalarArray>(
-        "channelName");
-    if (!channelNameField.get()) return false;
-    if (channelNameField->getElementType() != pvString) return false;
-
-    FieldConstPtr field = structure->getField("severity");
-    if (field.get())
-    {
-        ScalarArrayConstPtr severityField = structure->getField<ScalarArray>("severity");
-        if (!severityField.get() || severityField->getElementType() != pvInt)
-            return false;
-    }
-
-    field = structure->getField("status");
-    if (field.get())
-    {
-        ScalarArrayConstPtr statusField = structure->getField<ScalarArray>("status");
-        if (!statusField.get() || statusField->getElementType() != pvInt)
-            return false;
-    }
-
-    field = structure->getField("message");
-    if (field.get())
-    {
-        ScalarArrayConstPtr messageField = structure->getField<ScalarArray>("message");
-        if (!messageField.get() || messageField->getElementType() != pvString)
-           return false;
-    }
-
-    field = structure->getField("secondsPastEpoch");
-    if (field.get())
-    {
-        ScalarArrayConstPtr secondsPastEpochField = structure->getField<ScalarArray>("secondsPastEpoch");
-        if (!secondsPastEpochField.get() || secondsPastEpochField->getElementType() != pvLong)
-            return false;
-    }
-
-    field = structure->getField("nanoseconds");
-    if (field.get())
-    {
-        ScalarArrayConstPtr nanosecondsField = structure->getField<ScalarArray>("nanoseconds");
-        if (!nanosecondsField.get() || nanosecondsField->getElementType() != pvInt)
-            return false;
-    }
-
-    field = structure->getField("userTag");
-    if (field.get())
-    {
-        ScalarArrayConstPtr userTagField = structure->getField<ScalarArray>("userTag");
-        if (!userTagField.get() || userTagField->getElementType() != pvInt)
-            return false;
-    }
-
-    field = structure->getField("descriptor");
-    if (field.get())
-    {
-        ScalarConstPtr descriptorField = structure->getField<Scalar>("descriptor");
-        if (!descriptorField.get() || descriptorField->getScalarType() != pvString)
-            return false;
-    }
-
-    NTFieldPtr ntField = NTField::get();
-
-    field = structure->getField("alarm");
-    if (field.get() && !ntField->isAlarm(field))
+    if (!structure)
        return false;

-    field = structure->getField("timeStamp");
-    if (field.get() && !ntField->isTimeStamp(field))
-        return false;
+    Result result(structure);

-    return true;
+    return result
+        .is<Structure>()
+        .has<UnionArray>("value")
+        .has<ScalarArray>("channelName")
+        .maybeHas<ScalarArray>("severity")
+        .maybeHas<ScalarArray>("status")
+        .maybeHas<ScalarArray>("message")
+        .maybeHas<ScalarArray>("secondsPastEpoch")
+        .maybeHas<ScalarArray>("nanoseconds")
+        .maybeHas<ScalarArray>("userTag")
+        .maybeHas<Scalar>("descriptor")
+        .maybeHas<&NTField::isAlarm, Structure>("alarm")
+        .maybeHas<&NTField::isTimeStamp, Structure>("timeStamp")
+        .valid();
 }

-
 bool NTMultiChannel::isCompatible(PVStructurePtr const &pvStructure)
 {
    if(!pvStructure.get()) return false;
--- a/src/ntnameValue.cpp
+++ b/src/ntnameValue.cpp
@@ -4,6 +4,8 @@
 * found in the file LICENSE that is included with the distribution
 */

+#include "validator.h"
+
 #define epicsExportSharedSymbols
 #include <pv/ntnameValue.h>
 #include <pv/ntutils.h>
@@ -134,35 +136,19 @@ bool NTNameValue::is_a(PVStructurePtr const & pvStructure)

 bool NTNameValue::isCompatible(StructureConstPtr const & structure)
 {
-    if (structure.get() == 0) return false;
-
-    ScalarArrayConstPtr nameField = structure->getField<ScalarArray>("name");
-    if (nameField.get() == 0 || nameField->getElementType() != pvString)
+    if (!structure)
        return false;

-    ScalarArrayConstPtr valueField = structure->getField<ScalarArray>("value");
-    if (valueField.get() == 0)
-        return false;
-
-    FieldConstPtr field = structure->getField("descriptor");
-    if (field.get())
-    {
-        ScalarConstPtr descriptorField = structure->getField<Scalar>("descriptor");
-        if (!descriptorField || descriptorField->getScalarType() != pvString)
-            return false;
-    }
-
-    NTFieldPtr ntField = NTField::get();
-
-    field = structure->getField("alarm");
-    if (field && !ntField->isAlarm(field))
-        return false;
-
-    field = structure->getField("timeStamp");
-    if (field && !ntField->isTimeStamp(field))
-        return false;
-
-    return true;
+    Result result(structure);
+    
+    return result
+        .is<Structure>()
+        .has<ScalarArray>("name")
+        .has<ScalarArray>("value")
+        .maybeHas<Scalar>("descriptor")
+        .maybeHas<&NTField::isAlarm, Structure>("alarm")
+        .maybeHas<&NTField::isTimeStamp, Structure>("timeStamp")
+        .valid();
 }

 bool NTNameValue::isCompatible(PVStructurePtr const & pvStructure)
--- a/src/ntndarray.cpp
+++ b/src/ntndarray.cpp
@@ -7,6 +7,9 @@
 #include <algorithm>

 #include <pv/lock.h>
+#include <pv/sharedPtr.h>
+
+#include "validator.h"

 #define epicsExportSharedSymbols
 #include <pv/ntndarray.h>
@@ -18,9 +21,6 @@ using namespace epics::pvData;

 namespace epics { namespace nt {

-static NTFieldPtr ntField = NTField::get();
-
-
 namespace detail {

 static FieldCreatePtr fieldCreate = getFieldCreate();
@@ -192,95 +192,11 @@ NTNDArrayBuilder::shared_pointer NTNDArrayBuilder::add(string const & name, Fiel
    return shared_from_this();
 }

-
 }

 const std::string NTNDArray::URI("epics:nt/NTNDArray:1.0");
 const std::string ntAttrStr("epics:nt/NTAttribute:1.0");

-static FieldCreatePtr fieldCreate = getFieldCreate();
-static PVDataCreatePtr pvDataCreate = getPVDataCreate();
-
-class NTValueType
-{
-public:
-    static bool isCompatible(UnionConstPtr const &u)
-    {
-        if(!u.get()) return false;
-
-        if (u->getID() != Union::defaultId()) return false;
-        if (u->isVariant()) return false;
-
-        for (int i = pvBoolean; i != pvString; ++i)
-        {
-            ScalarType scalarType = static_cast<ScalarType>(i);
-            std::string name(ScalarTypeFunc::name(scalarType));
-            name += "Value";
-            ScalarArrayConstPtr scalarField = u->getField<ScalarArray>(name);
-            if (scalarField.get() == 0 ||
-                    scalarField->getElementType() != scalarType)
-                return false;
-        }
-
-        return true;
-    }
-};
-
-class NTCodec
-{
-public:
-    static bool isCompatible(StructureConstPtr const &structure)
-    {
-        if(!structure.get()) return false;
-
-        if (structure->getID() != "codec_t") return false;
-
-        ScalarConstPtr scalarField = structure->getField<Scalar>("name");
-        if (scalarField.get() == 0 || scalarField->getScalarType() != pvString)
-            return false;
-
-        UnionConstPtr paramField = structure->getField<Union>("parameters");
-        if (paramField.get() == 0 || !paramField->isVariant())
-            return false;
-
-        return true;
-    }
-};
-
-
-class NTDimension
-{
-public:
-    static bool isCompatible(StructureConstPtr const &structure)
-    {
-        if(!structure.get()) return false;
-
-        if (structure->getID() != "dimension_t") return false;
-
-        ScalarConstPtr scalarField = structure->getField<Scalar>("size");
-        if (scalarField.get() == 0 || scalarField->getScalarType() != pvInt)
-            return false;
-
-        scalarField = structure->getField<Scalar>("offset");
-        if (scalarField.get() == 0 || scalarField->getScalarType() != pvInt)
-            return false;
-
-        scalarField = structure->getField<Scalar>("fullSize");
-        if (scalarField.get() == 0 || scalarField->getScalarType() != pvInt)
-            return false;
-
-        scalarField = structure->getField<Scalar>("binning");
-        if (scalarField.get() == 0 || scalarField->getScalarType() != pvInt)
-            return false;
-
-        scalarField = structure->getField<Scalar>("reverse");
-        if (scalarField.get() == 0 || scalarField->getScalarType() != pvBoolean)
-            return false;
-
-        return true;
-    }
-};
-
 NTNDArray::shared_pointer NTNDArray::wrap(PVStructurePtr const & pvStructure)
 {
    if(!isCompatible(pvStructure)) return shared_pointer();
@@ -302,84 +218,62 @@ bool NTNDArray::is_a(PVStructurePtr const & pvStructure)
    return is_a(pvStructure->getStructure());
 }

-bool NTNDArray::isCompatible(StructureConstPtr const &structure)
-{
-    if(!structure.get()) return false;
-
-    UnionConstPtr valueField = structure->getField<Union>("value");
-    if(!NTValueType::isCompatible(valueField)) return false;
-
-    StructureConstPtr codecField = structure->getField<Structure>("codec");
-    if(!NTCodec::isCompatible(codecField)) return false;
-
-    ScalarConstPtr compressedSizeField = structure->getField<Scalar>("compressedSize");
-    if (compressedSizeField.get() == 0)
-        return false;
-
-    if (compressedSizeField->getScalarType() != pvLong)
-        return false;
-
-
-    ScalarConstPtr uncompressedSizeField = structure->getField<Scalar>("uncompressedSize");
-    if (uncompressedSizeField.get() == 0)
-        return false;
-
-    if (uncompressedSizeField->getScalarType() != pvLong)
-        return false;
-
-    StructureArrayConstPtr dimensionField = structure->getField<StructureArray>("dimension");
-    if (dimensionField.get() == 0)
-        return false;
-    StructureConstPtr dimElementStruc = dimensionField->getStructure();
-
-    if(!NTDimension::isCompatible(dimElementStruc))
-       return false;
-
-    NTFieldPtr ntField = NTField::get();
-
-    StructureConstPtr dataTimeStampField = structure->getField<Structure>(
-        "dataTimeStamp");
-    if (dataTimeStampField.get() == 0 || !ntField->isTimeStamp(dataTimeStampField))
-        return false;
-
-
-    ScalarConstPtr uniqueIdField = structure->getField<Scalar>("uniqueId");
-    if (uniqueIdField.get() == 0)
-        return false;
-
-    if (uniqueIdField->getScalarType() != pvInt)
-        return false;
-
-
-    StructureArrayConstPtr attributeField = structure->getField<StructureArray>( "attribute");
-    if (!attributeField)
-        return false;
-
-    if (!NTNDArrayAttribute::isCompatible(attributeField->getStructure()))
-        return false;
-
-
-    FieldConstPtr field = structure->getField("descriptor");
-    if (field.get())
+namespace {
+    Result& isValue(Result& result)
    {
-        ScalarConstPtr descriptorField = structure->getField<Scalar>("descriptor");
-        if (!descriptorField || descriptorField->getScalarType() != pvString)
-            return false;
+        result.is<Union>(Union::defaultId());
+
+        for (int i = pvBoolean; i < pvString; ++i) {
+            ScalarType type = static_cast<ScalarType>(i);
+            string name(ScalarTypeFunc::name(type));
+            result.has<ScalarArray>(name + "Value");
+        }
+
+        return result;
    }

-    field = structure->getField("alarm");
-    if (field.get() && !ntField->isAlarm(field))
+    Result& isCodec(Result& result)
+    {
+        return result
+            .is<Structure>("codec_t")
+            .has<Scalar>("name")
+            .has<Union>("parameters");
+    }
+
+    Result& isDimension(Result& result)
+    {
+        return result
+            .is<StructureArray>("dimension_t[]")
+            .has<Scalar>("size")
+            .has<Scalar>("offset")
+            .has<Scalar>("fullSize")
+            .has<Scalar>("binning")
+            .has<Scalar>("reverse");
+    }
+}
+
+bool NTNDArray::isCompatible(StructureConstPtr const &structure)
+{
+    if (!structure)
        return false;

-    field = structure->getField("timeStamp");
-    if (field.get() && !ntField->isTimeStamp(field))
-        return false;
+    Result result(structure);

-    field = structure->getField("display");
-    if (field.get() && !ntField->isDisplay(field))
-        return false;
-
-    return true;
+    return result
+        .is<Structure>()
+        .has<&isValue>("value")
+        .has<&isCodec>("codec")
+        .has<Scalar>("compressedSize")
+        .has<Scalar>("uncompressedSize")
+        .has<&isDimension>("dimension")
+        .has<Scalar>("uniqueId")
+        .has<&NTField::isTimeStamp, Structure>("dataTimeStamp")
+        .has<&NTNDArrayAttribute::isAttribute, StructureArray>("attribute")
+        .maybeHas<Scalar>("descriptor")
+        .maybeHas<&NTField::isAlarm, Structure>("alarm")
+        .maybeHas<&NTField::isTimeStamp, Structure>("timeStamp")
+        .maybeHas<&NTField::isDisplay, Structure>("display")
+        .valid();
 }


@@ -390,7 +284,6 @@ bool NTNDArray::isCompatible(PVStructurePtr const & pvStructure)
    return isCompatible(pvStructure->getStructure());
 }

-
 bool NTNDArray::isValid()
 {
    int64 valueSize = getValueSize();
--- a/src/ntndarrayAttribute.cpp
+++ b/src/ntndarrayAttribute.cpp
@@ -4,6 +4,8 @@
 * found in the file LICENSE that is included with the distribution
 */

+#include "validator.h"
+
 #define epicsExportSharedSymbols
 #include <pv/ntndarrayAttribute.h>
 #include <pv/ntattribute.h>
@@ -132,24 +134,25 @@ bool NTNDArrayAttribute::is_a(PVStructurePtr const & pvStructure)
    return is_a(pvStructure->getStructure());
 }

+Result& NTNDArrayAttribute::isAttribute(Result& result) {
+    return result
+        .has<Scalar>("name")
+        .has<Union>("value")
+        .maybeHas<ScalarArray>("tags")
+        .has<Scalar>("descriptor")
+        .maybeHas<&NTField::isAlarm, Structure>("alarm")
+        .maybeHas<&NTField::isTimeStamp, Structure>("timeStamp")
+        .has<Scalar>("sourceType")
+        .has<Scalar>("source");
+}
+
 bool NTNDArrayAttribute::isCompatible(StructureConstPtr const & structure)
 {
-    if (!NTAttribute::isCompatible(structure)) return false;
-
-    // descriptor required field for attibute in an ndarray
-    ScalarConstPtr descriptorField = structure->getField<Scalar>("descriptor");
-    if (descriptorField.get() == 0 || descriptorField->getScalarType() != pvString)
+    if (!structure)
        return false;

-    ScalarConstPtr sourcedTypeField = structure->getField<Scalar>("sourceType");
-    if (sourcedTypeField.get() == 0 || sourcedTypeField->getScalarType() != pvInt)
-        return false;
-
-    ScalarConstPtr sourcedField = structure->getField<Scalar>("source");
-    if (sourcedField.get() == 0 || sourcedField->getScalarType() != pvString)
-        return false;
-
-    return true;
+    Result result(structure);
+    return isAttribute(result.is<Structure>()).valid();
 }

 bool NTNDArrayAttribute::isCompatible(PVStructurePtr const & pvStructure)
--- a/src/ntscalar.cpp
+++ b/src/ntscalar.cpp
@@ -4,6 +4,8 @@
 * found in the file LICENSE that is included with the distribution
 */

+#include "validator.h"
+
 #define epicsExportSharedSymbols
 #include <pv/ntscalar.h>
 #include <pv/ntutils.h>
@@ -152,42 +154,22 @@ bool NTScalar::is_a(PVStructurePtr const & pvStructure)

 bool NTScalar::isCompatible(StructureConstPtr const &structure)
 {
-    if (structure.get() == 0) return false;
-
-    ScalarConstPtr valueField = structure->getField<Scalar>("value");
-    if (valueField.get() == 0)
+    if (!structure)
        return false;

-    FieldConstPtr field = structure->getField("descriptor");
-    if (field.get())
-    {
-        ScalarConstPtr descriptorField = structure->getField<Scalar>("descriptor");
-        if (!descriptorField.get() || descriptorField->getScalarType() != pvString)
-            return false;
-    }
+    Result result(structure);

-    NTFieldPtr ntField = NTField::get();
-
-    field = structure->getField("alarm");
-    if (field.get() && !ntField->isAlarm(field))
-        return false;
-
-    field = structure->getField("timeStamp");
-    if (field.get() && !ntField->isTimeStamp(field))
-        return false;
-
-    field = structure->getField("display");
-    if (field.get() && !ntField->isDisplay(field))
-        return false;
-
-    field = structure->getField("control");
-    if (field.get() && !ntField->isControl(field))
-        return false;
-
-    return true;
+    return result
+        .is<Structure>()
+        .has<Scalar>("value")
+        .maybeHas<Scalar>("descriptor")
+        .maybeHas<&NTField::isAlarm, Structure>("alarm")
+        .maybeHas<&NTField::isTimeStamp, Structure>("timeStamp")
+        .maybeHas<&NTField::isDisplay, Structure>("display")
+        .maybeHas<&NTField::isControl, Structure>("control")
+        .valid();
 }

-
 bool NTScalar::isCompatible(PVStructurePtr const & pvStructure)
 {
    if(!pvStructure) return false;
--- a/src/ntscalarArray.cpp
+++ b/src/ntscalarArray.cpp
@@ -4,6 +4,8 @@
 * found in the file LICENSE that is included with the distribution
 */

+#include "validator.h"
+
 #define epicsExportSharedSymbols
 #include <pv/ntscalarArray.h>
 #include <pv/ntutils.h>
@@ -161,39 +163,20 @@ bool NTScalarArray::is_a(PVStructurePtr const & pvStructure)

 bool NTScalarArray::isCompatible(StructureConstPtr const & structure)
 {
-    if (structure.get() == 0) return false;
-
-    ScalarArrayConstPtr valueField = structure->getField<ScalarArray>("value");
-    if (valueField.get() == 0)
+    if (!structure)
        return false;

-    FieldConstPtr field = structure->getField("descriptor");
-    if (field.get())
-    {
-        ScalarConstPtr descriptorField = structure->getField<Scalar>("descriptor");
-        if (!descriptorField.get() || descriptorField->getScalarType() != pvString)
-            return false;
-    }
+    Result result(structure);

-    NTFieldPtr ntField = NTField::get();
-
-    field = structure->getField("alarm");
-    if (field.get() && !ntField->isAlarm(field))
-        return false;
-
-    field = structure->getField("timeStamp");
-    if (field.get() && !ntField->isTimeStamp(field))
-        return false;
-
-    field = structure->getField("display");
-    if (field.get() && !ntField->isDisplay(field))
-        return false;
-
-    field = structure->getField("control");
-    if (field.get() && !ntField->isControl(field))
-        return false;
-
-    return true;
+    return result
+        .is<Structure>()
+        .has<ScalarArray>("value")
+        .maybeHas<Scalar>("descriptor")
+        .maybeHas<&NTField::isAlarm, Structure>("alarm")
+        .maybeHas<&NTField::isTimeStamp, Structure>("timeStamp")
+        .maybeHas<&NTField::isDisplay, Structure>("display")
+        .maybeHas<&NTField::isControl, Structure>("control")
+        .valid();
 }

 bool NTScalarArray::isCompatible(PVStructurePtr const & pvStructure)
--- a/src/ntscalarMultiChannel.cpp
+++ b/src/ntscalarMultiChannel.cpp
@@ -4,6 +4,7 @@
 * found in the file LICENSE that is included with the distribution
 */
 #include <algorithm>
+#include "validator.h"

 #define epicsExportSharedSymbols
 #include <pv/ntscalarMultiChannel.h>
@@ -228,86 +229,27 @@ bool NTScalarMultiChannel::is_a(PVStructurePtr const & pvStructure)

 bool NTScalarMultiChannel::isCompatible(StructureConstPtr const & structure)
 {
-    if (!structure.get()) return false;
-
-    ScalarArrayConstPtr valueField = structure->getField<ScalarArray>("value");
-    if (!valueField.get()) return false;
-
-    ScalarArrayConstPtr channelNameField = structure->getField<ScalarArray>(
-        "channelName");
-    if (!channelNameField.get()) return false;
-    if (channelNameField->getElementType() != pvString) return false;
-
-    FieldConstPtr field = structure->getField("severity");
-    if (field.get())
-    {
-        ScalarArrayConstPtr severityField = structure->getField<ScalarArray>("severity");
-        if (!severityField.get() || severityField->getElementType() != pvInt)
-            return false;
-    }
-
-    field = structure->getField("status");
-    if (field.get())
-    {
-        ScalarArrayConstPtr statusField = structure->getField<ScalarArray>("status");
-        if (!statusField.get() || statusField->getElementType() != pvInt)
-            return false;
-    }
-
-    field = structure->getField("message");
-    if (field.get())
-    {
-        ScalarArrayConstPtr messageField = structure->getField<ScalarArray>("message");
-        if (!messageField.get() || messageField->getElementType() != pvString)
-           return false;
-    }
-
-    field = structure->getField("secondsPastEpoch");
-    if (field.get())
-    {
-        ScalarArrayConstPtr secondsPastEpochField = structure->getField<ScalarArray>("secondsPastEpoch");
-        if (!secondsPastEpochField.get() || secondsPastEpochField->getElementType() != pvLong)
-            return false;
-    }
-
-    field = structure->getField("nanoseconds");
-    if (field.get())
-    {
-        ScalarArrayConstPtr nanosecondsField = structure->getField<ScalarArray>("nanoseconds");
-        if (!nanosecondsField.get() || nanosecondsField->getElementType() != pvInt)
-            return false;
-    }
-
-    field = structure->getField("userTag");
-    if (field.get())
-    {
-        ScalarArrayConstPtr userTagField = structure->getField<ScalarArray>("userTag");
-        if (!userTagField.get() || userTagField->getElementType() != pvInt)
-            return false;
-    }
-
-    field = structure->getField("descriptor");
-    if (field.get())
-    {
-        ScalarConstPtr descriptorField = structure->getField<Scalar>("descriptor");
-        if (!descriptorField.get() || descriptorField->getScalarType() != pvString)
-            return false;
-    }
-
-    NTFieldPtr ntField = NTField::get();
-
-    field = structure->getField("alarm");
-    if (field.get() && !ntField->isAlarm(field))
+    if (!structure)
        return false;

-    field = structure->getField("timeStamp");
-    if (field.get() && !ntField->isTimeStamp(field))
-        return false;
+    Result result(structure);

-    return true;
+    return result
+        .is<Structure>()
+        .has<ScalarArray>("value")
+        .has<ScalarArray>("channelName")
+        .maybeHas<ScalarArray>("severity")
+        .maybeHas<ScalarArray>("status")
+        .maybeHas<ScalarArray>("message")
+        .maybeHas<ScalarArray>("secondsPastEpoch")
+        .maybeHas<ScalarArray>("nanoseconds")
+        .maybeHas<ScalarArray>("userTag")
+        .maybeHas<Scalar>("descriptor")
+        .maybeHas<&NTField::isAlarm, Structure>("alarm")
+        .maybeHas<&NTField::isTimeStamp, Structure>("timeStamp")
+        .valid();
 }

-
 bool NTScalarMultiChannel::isCompatible(PVStructurePtr const &pvStructure)
 {
    if(!pvStructure.get()) return false;
--- a/src/nttable.cpp
+++ b/src/nttable.cpp
@@ -5,6 +5,7 @@
 */

 #include <algorithm>
+#include "validator.h"

 #define epicsExportSharedSymbols
 #include <pv/nttable.h>
@@ -149,42 +150,32 @@ bool NTTable::is_a(PVStructurePtr const & pvStructure)

 bool NTTable::isCompatible(StructureConstPtr const & structure)
 {
-    if (!structure.get()) return false;
-
-    StructureConstPtr valueField = structure->getField<Structure>("value");
-    if (!valueField.get())
+    if (!structure)
        return false;

-    FieldConstPtrArray const & fields = valueField->getFields();
-    for (FieldConstPtrArray::const_iterator it = fields.begin();
-         it != fields.end(); ++it)
-    {
-        if ((*it)->getType() != scalarArray) return false;
+    Result result(structure);
+
+    result
+        .is<Structure>()
+        .has<Structure>("value")
+        .has<ScalarArray>("labels")
+        .maybeHas<Scalar>("descriptor")
+        .maybeHas<&NTField::isAlarm, Structure>("alarm")
+        .maybeHas<&NTField::isTimeStamp, Structure>("timeStamp");
+
+    StructureConstPtr value(structure->getField<Structure>("value"));
+    if (value) {
+        Result r(value);
+        StringArray const & names(value->getFieldNames());
+        StringArray::const_iterator it;
+
+        for (it = names.begin(); it != names.end(); ++it)
+            r.has<ScalarArray>(*it);
+
+        result |= r;
    }

-    ScalarArrayConstPtr labelsField = structure->getField<ScalarArray>("labels");
-    if (!labelsField.get() || labelsField->getElementType() != pvString)
-        return false;
-
-    FieldConstPtr field = structure->getField("descriptor");
-    if (field.get())
-    {
-        ScalarConstPtr descriptorField = structure->getField<Scalar>("descriptor");
-        if (!descriptorField.get() || descriptorField->getScalarType() != pvString)
-            return false;
-    }
-
-    NTFieldPtr ntField = NTField::get();
-
-    field = structure->getField("alarm");
-    if (field.get() && !ntField->isAlarm(field))
-        return false;
-
-    field = structure->getField("timeStamp");
-    if (field.get() && !ntField->isTimeStamp(field))
-        return false;
-
-    return true;
+    return result.valid();
 }

 bool NTTable::isCompatible(PVStructurePtr const & pvStructure)
@@ -270,7 +261,7 @@ PVStringArrayPtr NTTable::getLabels() const

 StringArray const & NTTable::getColumnNames() const
 {
-    return pvNTTable->getStructure()->getFieldNames();
+    return pvValue->getStructure()->getFieldNames();
 }

 PVFieldPtr NTTable::getColumn(std::string const & columnName) const
--- a/src/ntunion.cpp
+++ b/src/ntunion.cpp
@@ -4,6 +4,8 @@
 * found in the file LICENSE that is included with the distribution
 */

+#include "validator.h"
+
 #define epicsExportSharedSymbols
 #include <pv/ntunion.h>
 #include <pv/ntutils.h>
@@ -128,31 +130,18 @@ bool NTUnion::is_a(PVStructurePtr const & pvStructure)

 bool NTUnion::isCompatible(StructureConstPtr const &structure)
 {
-    if (structure.get() == 0) return false;
-
-    UnionConstPtr valueField = structure->getField<Union>("value");
-    if (valueField.get() == 0)
+    if (!structure)
        return false;

-    FieldConstPtr field = structure->getField("descriptor");
-    if (field.get())
-    {
-        ScalarConstPtr descriptorField = structure->getField<Scalar>("descriptor");
-        if (!descriptorField.get() || descriptorField->getScalarType() != pvString)
-            return false;
-    }
+    Result result(structure);

-    NTFieldPtr ntField = NTField::get();
-
-    field = structure->getField("alarm");
-    if (field.get() && !ntField->isAlarm(field))
-        return false;
-
-    field = structure->getField("timeStamp");
-    if (field.get() && !ntField->isTimeStamp(field))
-        return false;
-
-    return true;
+    return result
+        .is<Structure>()
+        .has<Union>("value")
+        .maybeHas<Scalar>("descriptor")
+        .maybeHas<&NTField::isAlarm, Structure>("alarm")
+        .maybeHas<&NTField::isTimeStamp, Structure>("timeStamp")
+        .valid();
 }

 bool NTUnion::isCompatible(PVStructurePtr const & pvStructure)
--- a/src/nturi.cpp
+++ b/src/nturi.cpp
@@ -5,6 +5,7 @@
 */

 #include <algorithm>
+#include "validator.h"

 #define epicsExportSharedSymbols
 #include <pv/nturi.h>
@@ -149,45 +150,31 @@ bool NTURI::is_a(PVStructurePtr const & pvStructure)

 bool NTURI::isCompatible(StructureConstPtr const & structure)
 {
-    if (!structure.get()) return false;
-
-    ScalarConstPtr schemeField = structure->getField<Scalar>("scheme");
-    if (schemeField.get() == 0 || schemeField->getScalarType() != pvString)
+    if (!structure)
        return false;

-    ScalarConstPtr pathField = structure->getField<Scalar>("path");
-    if (pathField.get() == 0 || pathField->getScalarType() != pvString)
-        return false;
+    Result result(structure);

-    FieldConstPtr field = structure->getField("authority");
-    if (field.get())
-    {
-        ScalarConstPtr authorityField = structure->getField<Scalar>("authority");
-        if (!authorityField.get() || authorityField->getScalarType() != pvString)
-            return false;
+    result
+        .is<Structure>()
+        .has<Scalar>("scheme")
+        .has<Scalar>("path")
+        .maybeHas<Scalar>("authority")
+        .maybeHas<Structure>("query");
+
+    StructureConstPtr query(structure->getField<Structure>("query"));
+    if (query) {
+        Result r(query);
+        StringArray const & names(query->getFieldNames());
+        StringArray::const_iterator it;
+
+        for (it = names.begin(); it != names.end(); ++it)
+            r.has<ScalarArray>(*it);
+
+        result |= r;
    }

-    field = structure->getField("query");
-    if (field.get())
-    {
-        StructureConstPtr queryField = structure->getField<Structure>("query");
-        if (!queryField.get())
-            return false;
-
-        FieldConstPtrArray const & fields = queryField->getFields();
-        for (FieldConstPtrArray::const_iterator it = fields.begin();
-             it != fields.end(); ++it)
-        {
-            if ((*it)->getType() != scalar) return false;
-            ScalarType scalarType = std::tr1::dynamic_pointer_cast<const Scalar>(
-               (*it))->getScalarType();
-            if (scalarType != pvString &&
-                scalarType != pvInt &&
-                scalarType != pvDouble) return false;
-        }
-    }
-
-    return true;
+    return result.valid();
 }


--- a/src/pv/ntcontinuum.h
+++ b/src/pv/ntcontinuum.h
@@ -93,7 +93,6 @@ namespace detail {

        void reset();

-        bool dim;
        bool descriptor;
        bool alarm;
        bool timeStamp;
--- a/src/pv/ntfield.h
+++ b/src/pv/ntfield.h
@@ -30,6 +30,8 @@

 namespace epics { namespace nt {

+struct Result;
+
 class NTField;
 typedef std::tr1::shared_ptr<NTField> NTFieldPtr;

@@ -149,6 +151,30 @@ private:
    NTField();
    epics::pvData::FieldCreatePtr fieldCreate;
    epics::pvData::StandardFieldPtr standardField;
+
+    // These won't be public just yet
+    static Result& isEnumerated(Result&);
+    static Result& isTimeStamp(Result&);
+    static Result& isAlarm(Result&);
+    static Result& isDisplay(Result&);
+    static Result& isAlarmLimit(Result&);
+    static Result& isControl(Result&);
+
+    friend class NTAggregate;
+    friend class NTAttribute;
+    friend class NTContinuum;
+    friend class NTEnum;
+    friend class NTHistogram;
+    friend class NTMatrix;
+    friend class NTMultiChannel;
+    friend class NTNameValue;
+    friend class NTNDArray;
+    friend class NTNDArrayAttribute;
+    friend class NTScalar;
+    friend class NTScalarArray;
+    friend class NTScalarMultiChannel;
+    friend class NTTable;
+    friend class NTUnion;
 };

 /**
@@ -197,12 +223,6 @@ public:
     */
    epics::pvData::PVStructurePtr createDisplay();

-    /**
-     * Creates an alarmLimit PVStructure.
-     * @return an alarmLimit PVStructure.
-     */
-    epics::pvData::PVStructurePtr createAlarmLimit();
-
    /**
     * Creates a control PVStructure.
     * @return a control PVStructure.
--- a/src/pv/nthistogram.h
+++ b/src/pv/nthistogram.h
@@ -103,7 +103,6 @@ namespace detail {
        bool valueTypeSet;
        epics::pvData::ScalarType valueType;

-        bool dim;
        bool descriptor;
        bool alarm;
        bool timeStamp;
--- a/src/pv/ntndarray.h
+++ b/src/pv/ntndarray.h
@@ -10,16 +10,16 @@
 #include <string>

 #ifdef epicsExportSharedSymbols
-#   define ntscalarArrayEpicsExportSharedSymbols
+#   define ntndarrayEpicsExportSharedSymbols
 #   undef epicsExportSharedSymbols
 #endif

 #include <pv/pvDisplay.h>
 #include <pv/pvControl.h>

-#ifdef ntscalarArrayEpicsExportSharedSymbols
+#ifdef ntndarrayEpicsExportSharedSymbols
 #   define epicsExportSharedSymbols
-#	undef ntscalarArrayEpicsExportSharedSymbols
+#	undef ntndarrayEpicsExportSharedSymbols
 #endif

 #include <pv/ntfield.h>
@@ -139,7 +139,7 @@ public:
     * and if so returns an NTScalarArray which wraps it.
     * This method will return null if the structure is is not compatible
     * or is null.
-     * 
+     *
     * @param pvStructure the PVStructure to be wrapped
     * @return NTScalarArray instance wrapping pvStructure on success, null otherwise
     */
@@ -150,7 +150,7 @@ public:
     * <p>
     * No checks are made as to whether the specified PVStructure
     * is compatible with NTNDArray or is non-null.
-     * 
+     *
     * @param pvStructure the PVStructure to be wrapped
     * @return NTNDArray instance wrapping pvStructure
     */
@@ -163,7 +163,7 @@ public:
     * version of NTNDArray through its type ID, including checking version numbers.
     * The return value does not depend on whether the structure is actually
     * compatible in terms of its introspection type.
-     * 
+     *
     * @param structure the pvStructure to test
     * @return (false,true) if the specified Structure (is not, is) a compatible NTNDArray
     */
@@ -176,7 +176,7 @@ public:
     * version of NTNDArray through its type ID, including checking version numbers.
     * The return value does not depend on whether the structure is actually
     * compatible in terms of its introspection type.
-     * 
+     *
     * @param pvStructure the PVStructure to test
     * @return (false,true) if the specified PVStructure (is not, is) a compatible NTNDArray
     */
@@ -187,7 +187,7 @@ public:
     * <p>
     * Checks if the specified Structure is compatible with this version
     * of NTNDArray through the introspection interface.
-     * 
+     *
     * @param structure the Structure to test
     * @return (false,true) if the specified Structure (is not, is) a compatible NTNDArray
     */
--- a/src/pv/ntndarrayAttribute.h
+++ b/src/pv/ntndarrayAttribute.h
@@ -22,6 +22,7 @@

 namespace epics { namespace nt {

+struct Result;
 class NTNDArrayAttribute;
 typedef std::tr1::shared_ptr<NTNDArrayAttribute> NTNDArrayAttributePtr;

@@ -302,10 +303,13 @@ public:

 private:
    NTNDArrayAttribute(epics::pvData::PVStructurePtr const & pvStructure);
+    static Result& isAttribute(Result& result);
+
    epics::pvData::PVStructurePtr pvNTNDArrayAttribute;
    epics::pvData::PVUnionPtr pvValue;

    friend class detail::NTNDArrayAttributeBuilder;
+    friend class NTNDArray;
 };

 }}
--- a/src/validator.h
+++ b/src/validator.h
@@ -0,0 +1,277 @@
+/* validator.h */
+/*
+ * Copyright information and license terms for this software can be
+ * found in the file LICENSE that is included with the distribution
+ */
+#ifndef VALIDATOR_H
+#define VALIDATOR_H
+
+#include <string>
+#include <set>
+#include <algorithm>
+
+#include <pv/pvIntrospect.h>
+
+namespace epics { namespace nt {
+
+/**
+ * @brief Validation methods for NT types.
+ *
+ * @author bsm
+ */
+
+struct Result {
+    struct Error {
+        std::string path;
+        enum Type {
+            MissingField,
+            IncorrectType,
+            IncorrectId,
+        } type;
+
+        Error(std::string const & path, Type type)
+        : path(path), type(type) {}
+
+        bool operator==(const Error& other) const {
+            return type == other.type && path == other.path;
+        }
+
+        std::ostream& dump(std::ostream& os) const {
+            os << "Error(path=" << (path.empty() ? "<root>" : path) << ": ";
+
+            switch(type) {
+                case MissingField:  os << "missing";        break;
+                case IncorrectType: os << "incorrect type"; break;
+                case IncorrectId:   os << "incorrect ID";   break;
+            }
+            os << ")";
+            return os;
+        }
+    };
+
+    epics::pvData::FieldConstPtr field;
+    std::string path;
+    std::vector<Error> errors;
+
+    enum result_t {
+        Pass,
+        Fail,
+    } result;
+
+    Result(const epics::pvData::FieldConstPtr& field, const std::string& path = std::string())
+    : field(field), path(path), errors(), result(Pass) {}
+
+    Result() {}
+
+    Result& operator|=(const Result& other) {
+        result = std::max(result, other.result);
+        errors.insert(errors.end(), other.errors.begin(), other.errors.end());
+        return *this;
+    }
+
+    /**
+     * Returns whether this Result is valid.
+     *
+     * @return true if all tests passed, false otherwise.
+     */
+    inline bool valid(void) const {
+        return result == Pass;
+    }
+
+    /**
+     * Test that this Result's field is of a particular type 'T'.
+     *
+     * Appends an Error::Type::IncorrectType if the field is not of type 'T'.
+     *
+     * @return itself
+     */
+    template<typename T>
+    Result& is(void) {
+        if (!dynamic_cast<T const *>(field.get())) {
+            result = Fail;
+            errors.push_back(Error(path, Error::IncorrectType));
+        }
+        return *this;
+    }
+
+    /**
+     * Test that this Result's field is of a particular type 'T' and has
+     * an ID equal to 'id'.
+     *
+     * Appends an Error::Type::IncorrectType if the field is not of type 'T'.
+     * Appends an Error::Type::IncorrectId if the field does not have an ID
+     * equal to 'id'.
+     *
+     * @return itself
+     */
+    template<typename T>
+    Result& is(const std::string& id) {
+        T const *s = dynamic_cast<T const *>(field.get());
+        if (!s) {
+            result = Fail;
+            errors.push_back(Error(path, Error::IncorrectType));
+        } else if (s->getID() != id) {
+            result = Fail;
+            errors.push_back(Error(path, Error::IncorrectId));
+        }
+        return *this;
+    }
+
+    /**
+     * Test that this Result's field has a subfield with name 'name' and
+     * apply the function 'fn' to the subfield.
+     *
+     * Appends an Error::Type::IncorrectType if the field is not one of
+     * Structure, StructureArray, Union, UnionArray.
+     * Appends an Error::Type::MissingField if the subfield is not
+     * present.
+     *
+     * @return itself
+     */
+    template<Result& (*fn)(Result&)>
+    Result& has(const std::string& name) {
+        return has<epics::pvData::Field>(name, false, fn);
+    }
+
+    /**
+     * Test that this Result's field has an optional subfield with name
+     * 'name' and, if it has, apply the function 'fn' to the subfield.
+     *
+     * Appends an Error::Type::IncorrectType if the field is not one of
+     * Structure, StructureArray, Union, UnionArray.
+     *
+     * @return itself
+     */
+    template<Result& (*fn)(Result&)>
+    Result& maybeHas(const std::string& name) {
+        return has<epics::pvData::Field>(name, true, fn);
+    }
+
+    /**
+     * Test that this Result's field has a subfield with name 'name',
+     * apply the function 'fn' to the subfield and
+     * test that the subfield is of type 'T'.
+     *
+     * Appends an Error::Type::IncorrectType if the field is not one of
+     * Structure, StructureArray, Union, UnionArray.
+     * Appends an Error::Type::IncorrectType if the subfield is not of
+     * type 'T'.
+     * Appends an Error::Type::MissingField if the subfield is not
+     * present.
+     *
+     * @return itself
+     */
+    template<Result& (*fn)(Result&), typename T>
+    Result& has(const std::string& name) {
+        return has<T>(name, false, fn);
+    }
+
+    /**
+     * Test that this Result's field has an optional subfield with name
+     * 'name' and, if it has, apply the function 'fn' to the subfield and
+     * test that the subfield is of type 'T'.
+     *
+     * Appends an Error::Type::IncorrectType if the field is not one of
+     * Structure, StructureArray, Union, UnionArray.
+     * Appends an Error::Type::IncorrectType if the subfield exists and
+     * is not of type 'T'.
+     *
+     * @return itself
+     */
+    template<Result& (*fn)(Result&), typename T>
+    Result& maybeHas(const std::string& name) {
+        return has<T>(name, true, fn);
+    }
+
+    /**
+     * Test that this Result's field has a subfield with name 'name' and
+     * test that the subfield is of type 'T'.
+     *
+     * Appends an Error::Type::IncorrectType if the field is not one of
+     * Structure, StructureArray, Union, UnionArray.
+     * Appends an Error::Type::IncorrectType if the subfield is not of
+     * type 'T'.
+     * Appends an Error::Type::MissingField if the subfield is not
+     * present.
+     *
+     * @return itself
+     */
+    template<typename T>
+    Result& has(const std::string& name) {
+        return has<T>(name, false, NULL);
+    }
+
+    /**
+     * Test that this Result's field has an optional subfield with name
+     * 'name' and, if it has, test that the subfield is of type 'T'.
+     *
+     * Appends an Error::Type::IncorrectType if the field is not one of
+     * Structure, StructureArray, Union, UnionArray.
+     * Appends an Error::Type::IncorrectType if the subfield exists and
+     * is not of type 'T'.
+     *
+     * @return itself
+     */
+    template<typename T>
+    Result& maybeHas(const std::string& name) {
+        return has<T>(name, true, NULL);
+    }
+
+    std::ostream& dump(std::ostream& os) const {
+        os << "Result(valid=" << (result == Pass) << ", errors=[ ";
+
+        std::vector<Error>::const_iterator it;
+        for (it = errors.begin(); it != errors.end(); ++it) {
+            (*it).dump(os);
+            os << " ";
+        }
+        os << "])";
+        return os;
+    }
+
+private:
+    template<typename T>
+    Result& has(const std::string& name, bool optional, Result& (*check)(Result&) = NULL) {
+        epics::pvData::FieldConstPtr subField;
+
+        switch(field->getType()) {
+            case epics::pvData::structure:
+                subField = static_cast<epics::pvData::Structure const *>(field.get())->getField(name);
+                break;
+            case epics::pvData::structureArray:
+                subField = static_cast<epics::pvData::StructureArray const *>(field.get())->getStructure()->getField(name);
+                break;
+            case epics::pvData::union_:
+                subField = static_cast<epics::pvData::Union const *>(field.get())->getField(name);
+                break;
+            case epics::pvData::unionArray:
+                subField = static_cast<epics::pvData::UnionArray const *>(field.get())->getUnion()->getField(name);
+                break;
+            default:
+                // Expected a structure-like Field
+                result = Fail;
+                errors.push_back(Error(path, Error::IncorrectType));
+                return *this;
+        }
+
+        std::string subFieldPath(path.empty() ? name : path + "." + name);
+
+        if (!subField) {
+            if (!optional) {
+                result = Fail;
+                errors.push_back(Error(subFieldPath, Error::MissingField));
+            }
+        } else if (!dynamic_cast<T const *>(subField.get())) {
+            result = Fail;
+            errors.push_back(Error(subFieldPath, Error::IncorrectType));
+        } else if (check) {
+            Result r(subField, subFieldPath);
+            *this |= check(r);
+        }
+
+        return *this;
+    }
+};
+}}
+
+#endif
--- a/test/Makefile
+++ b/test/Makefile
@@ -72,6 +72,10 @@ TESTPROD_HOST += ntutilsTest
 ntutilsTest_SRCS = ntutilsTest.cpp
 TESTS += ntutilsTest

+TESTPROD_HOST += validatorTest
+validatorTest_SRCS = validatorTest.cpp
+TESTS += validatorTest
+
 TESTSCRIPTS_HOST += $(TESTS:%=%.t)

 include $(TOP)/configure/RULES
--- a/test/ntmatrixTest.cpp
+++ b/test/ntmatrixTest.cpp
@@ -151,7 +151,6 @@ void test_ntmatrix()
        display.setLow(-15);
        display.setHigh(15);
        display.setDescription("This is a test scalar array");
-        display.setFormat("%d");
        display.setUnits("A");
        pvDisplay.set(display);
    }
--- a/test/ntscalarArrayTest.cpp
+++ b/test/ntscalarArrayTest.cpp
@@ -167,7 +167,6 @@ void test_ntscalarArray()
        display.setLow(-15);
        display.setHigh(15);
        display.setDescription("This is a test scalar array");
-        display.setFormat("%d");
        display.setUnits("A");
        pvDisplay.set(display);
    }
--- a/test/ntscalarTest.cpp
+++ b/test/ntscalarTest.cpp
@@ -159,7 +159,6 @@ void test_ntscalar()
        display.setLow(-15);
        display.setHigh(15);
        display.setDescription("This is a test scalar");
-        display.setFormat("%d");
        display.setUnits("A");
        pvDisplay.set(display);
    }
--- a/test/validatorTest.cpp
+++ b/test/validatorTest.cpp
@@ -0,0 +1,311 @@
+/*
+ * Copyright information and license terms for this software can be
+ * found in the file LICENSE that is included with the distribution
+ */
+
+#include <epicsUnitTest.h>
+#include <testMain.h>
+
+#include "../src/validator.h"
+#include <pv/ntndarray.h>
+#include <pv/pvIntrospect.h>
+
+using namespace epics::nt;
+using namespace epics::pvData;
+
+static epics::pvData::FieldCreatePtr FC;
+
+void test_is()
+{
+    testDiag("test_is");
+
+    // Result::is<Scalar> must be valid for Scalars of any type
+    for(int i = pvBoolean; i <= pvString; ++i) {
+        ScalarType t = static_cast<ScalarType>(i);
+        testOk(Result(FC->createScalar(t)).is<Scalar>().valid(),
+            "Result(Scalar<%s>).is<Scalar>().valid()", ScalarTypeFunc::name(t));
+    }
+
+    // Result::is<ScalarArray> must be valid for ScalarArray of any type
+    for(int i = pvBoolean; i <= pvString; ++i) {
+        ScalarType t = static_cast<ScalarType>(i);
+        testOk(Result(FC->createScalarArray(t)).is<ScalarArray>().valid(),
+            "Result(ScalarArray<%s>).is<ScalarArray>().valid()", ScalarTypeFunc::name(t));
+    }
+
+    {
+        // Result::is<Scalar> must be invalid for non-Scalar
+        Result result(FC->createScalarArray(pvInt));
+        result.is<Scalar>();
+        testOk(!result.valid(), "!Result(ScalarArray<pvInt>).is<Scalar>.valid()");
+        testOk1(result.errors.at(0) == Result::Error("", Result::Error::IncorrectType));
+    }
+
+    {
+        // Result::is<ScalarArray> must be invalid for non-ScalarArray
+        Result result(FC->createScalar(pvInt));
+        result.is<ScalarArray>();
+        testOk(!result.valid(), "!Result(ScalarArray<pvInt>).is<Scalar>.valid()");
+        testOk1(result.errors.at(0) == Result::Error("", Result::Error::IncorrectType));
+    }
+}
+
+void test_is_id()
+{
+    testDiag("test_is_id");
+
+    FieldBuilderPtr FB(FieldBuilder::begin());
+
+    {
+        // Both type and ID match for Structure
+        Result result(FB->setId("TEST_ID")->createStructure());
+        result.is<Structure>("TEST_ID");
+        testOk(result.valid(), "Result(Structure['TEST_ID']).is<Structure>('TEST_ID').valid()");
+    }
+
+    {
+        // Both type and ID match for Union
+        UnionConstPtr un(FB->
+            setId("TEST_ID")->
+            add("A", pvInt)->
+            add("B", pvString)->
+            createUnion()
+        );
+        Result result(un);
+        result.is<Union>("TEST_ID");
+        testOk(result.valid(), "Result(Union{A:int,B:string}['TEST_ID']).is<Union>('TEST_ID').valid()");
+    }
+
+    {
+        // Both type and ID match for Variant Union
+        Result result(FB-> createUnion());
+        result.is<Union>(Union::ANY_ID);
+        testOk(result.valid(), "Result(Union).is<Union>('%s').valid()", Union::ANY_ID.c_str());
+    }
+
+    {
+        // ID matches, type doesn't
+        Result result(FB->setId("TEST_ID")->createStructure());
+        result.is<Union>("TEST_ID");
+        testOk(!result.valid(), "!Result(Union['TEST_ID']).is<Structure>('TEST_ID').valid()");
+        testOk1(result.errors.at(0) == Result::Error("", Result::Error::IncorrectType));
+    }
+    
+    {
+        // Type matches, ID doesn't
+        Result result(FB->setId("WRONG_ID")->createStructure());
+        result.is<Structure>("TEST_ID");
+        testOk(!result.valid(), "!Result(Structure['WRONG_ID']).is<Structure>('TEST_ID').valid()");
+        testOk1(result.errors.at(0) == Result::Error("", Result::Error::IncorrectId));
+    }
+
+    {
+        // Neither type nor ID match (ID is not even checked in this case since it doesn't exist)
+        Result result(FC->createScalar(pvDouble));
+        result.is<Structure>("SOME_ID");
+        testOk(!result.valid(), "!Result(Scalar).is<Structure>('SOME_ID').valid()");
+        testOk1(result.errors.at(0) == Result::Error("", Result::Error::IncorrectType));
+    }
+}
+
+void test_has()
+{
+    testDiag("test_has");
+
+    FieldBuilderPtr FB(FieldBuilder::begin());
+
+    StructureConstPtr struc(FB->
+        add("A", pvInt)->
+        add("B", pvString)->
+        createStructure()
+    );
+
+    std::string strucRepr("Structure{A:int,B:String}");
+
+    {
+        // Test that struc has both A and B, both being Scalars
+        Result result(struc);
+        result
+           .has<Scalar>("A")
+           .has<Scalar>("B");
+
+        testOk(result.valid(),
+            "Result(%s).has<Scalar>('A').has<Scalar>('B').valid()",
+            strucRepr.c_str());
+    }
+
+    {
+        // Test that struc does not have a field B of type ScalarArray
+        Result result(struc);
+        result
+           .has<Scalar>("A")
+           .has<ScalarArray>("B");
+        testOk(!result.valid(), 
+            "!Result(%s).has<Scalar>('A').has<ScalarArray>('B').valid()",
+            strucRepr.c_str());
+        testOk1(result.errors.at(0) == Result::Error("B", Result::Error::IncorrectType));
+    }
+
+    {
+        // Test that struc does not have a field C
+        Result result(struc);
+        result
+           .has<Scalar>("A")
+           .has<Scalar>("C");
+        testOk(!result.valid(), 
+            "!Result(%s).has<Scalar>('A').has<Scalar>('C').valid()",
+            strucRepr.c_str());
+        testOk1(result.errors.at(0) == Result::Error("C", Result::Error::MissingField));
+    }
+
+    {
+        // Test that 'has' fails for non-structure-like Fields
+        Result result(FC->createScalar(pvByte));
+        result.has<Scalar>("X");
+        testOk(!result.valid(), "!Result(Scalar<pvByte>).has<Scalar>('X').valid()");
+        testOk1(result.errors.at(0) == Result::Error("", Result::Error::IncorrectType));
+    }
+}
+
+void test_maybe_has()
+{
+    testDiag("test_maybe_has");
+
+    FieldBuilderPtr FB(FieldBuilder::begin());
+
+    StructureConstPtr struc(FB->
+        add("A", pvInt)->
+        add("B", pvString)->
+        createStructure()
+    );
+
+    std::string strucRepr("Structure{A:int,B:String}");
+
+    {
+        // Test that struc maybe has A and B, both being Scalars
+        Result result(struc);
+        result
+           .maybeHas<Scalar>("A")
+           .maybeHas<Scalar>("B");
+
+        testOk(result.valid(),
+            "Result(%s).maybeHas<Scalar>('A').maybeHas<Scalar>('B').valid()",
+            strucRepr.c_str());
+    }
+
+    {
+        // Test that if struc has a field B, it must be of type ScalarArray
+        Result result(struc);
+        result
+           .maybeHas<Scalar>("A")
+           .maybeHas<ScalarArray>("B");
+        testOk(!result.valid(), 
+            "!Result(%s).maybeHas<Scalar>('A').maybeHas<ScalarArray>('B').valid()",
+            strucRepr.c_str());
+        testOk1(result.errors.at(0) == Result::Error("B", Result::Error::IncorrectType));
+    }
+
+    {
+        // Test that struc maybe has A (which it does) and B (which it doesn't)
+        Result result(struc);
+        result
+           .maybeHas<Scalar>("A")
+           .maybeHas<Scalar>("C");
+        testOk(result.valid(), 
+            "Result(%s).maybeHas<Scalar>('A').maybeHas<Scalar>('C').valid()",
+            strucRepr.c_str());
+    }
+
+    {
+        // Test that 'maybeHas' fails for non-structure-like Fields
+        Result result(FC->createScalar(pvByte));
+        result.maybeHas<Scalar>("X");
+        testOk(!result.valid(), "!Result(Scalar<pvByte>).maybeHas<Scalar>('X').valid()");
+        testOk1(result.errors.at(0) == Result::Error("", Result::Error::IncorrectType));
+    }
+}
+
+Result& isStructABC(Result& result)
+{
+    return result
+        .is<Structure>("ABC")
+        .has<Scalar>("A")
+        .has<ScalarArray>("B")
+        .maybeHas<Scalar>("C");
+}
+
+void test_has_fn()
+{
+    testDiag("test_has_fn");
+    FieldBuilderPtr FB(FieldBuilder::begin());
+
+    {
+        StructureConstPtr inner(FB->
+            setId("ABC")->
+            add("A", pvInt)->
+            addArray("B", pvDouble)->
+            add("C", pvString)->
+            createStructure()
+        );
+
+        Result result(FB->add("inner", inner)->createStructure());
+        result.has<&isStructABC>("inner");
+
+        testOk(result.valid(), "Result({inner:<valid structABC>}).has<&isStructAbc>('inner').valid()");
+    }
+
+    {
+        StructureConstPtr inner(FB->
+            setId("ABC")->
+            add("A", pvInt)->
+            addArray("B", pvDouble)->
+            createStructure()
+        );
+
+        Result result(FB->add("inner", inner)->createStructure());
+        result.has<&isStructABC>("inner");
+
+        testOk(result.valid(), "Result({inner:<valid structABC w/o C>}).has<&isStructAbc>('inner').valid()");
+    }
+
+    {
+        StructureConstPtr inner(FB->
+            setId("XYZ")->
+            add("A", pvInt)->
+            addArray("B", pvDouble)->
+            createStructure()
+        );
+
+        Result result(FB->add("inner", inner)->createStructure());
+        result.has<&isStructABC>("inner");
+
+        testOk(!result.valid(), "!Result({inner:<structABC wrong id>}).has<&isStructAbc>('inner').valid()");
+        testOk1(result.errors.at(0) == Result::Error("inner", Result::Error::IncorrectId));
+    }
+
+    {
+        StructureConstPtr inner(FB->
+            setId("XYZ")->
+            add("A", pvInt)->
+            add("B", pvDouble)->
+            createStructure()
+        );
+
+        Result result(FB->add("inner", inner)->createStructure());
+        result.has<&isStructABC>("inner");
+
+        testOk(!result.valid(), "!Result({inner:<structABC wrong id and fields>}).has<&isStructAbc>('inner').valid()");
+        testOk1(result.errors.size() == 2);
+    }
+}
+
+MAIN(testValidator) {
+    testPlan(56);
+    FC = epics::pvData::getFieldCreate();
+    test_is();
+    test_is_id();
+    test_has();
+    test_maybe_has();
+    test_has_fn();
+    return testDone();
+}
Author	SHA1	Message	Date
Andrew Johnson	c6168a7477	New CONFIG_NTYPES_VERSION file, use for SHRLIB_VERSION	2019-07-29 11:14:27 -05:00
Bruno Martins	dd2aa1863d	Bump SHRLIB version	2019-07-26 17:04:30 -04:00
Bruno Martins	66737740ef	Add isCompatible reimplementation note to RELEASE_NOTES	2019-07-26 17:02:28 -04:00
Bruno Martins	54bddc9942	NTNDArrayAttribute: fix forward declaration of Result	2019-06-14 11:43:42 -04:00
Bruno Martins	02151964a9	NTField: fix forward declaration of Result	2019-06-14 08:41:27 -04:00
Bruno Martins	d366cc9682	Validator: explicitly include <algorithm>	2019-06-14 08:41:10 -04:00
Bruno Martins	1cac2ccd7e	Add -DNOMINMAX to Windows builds	2019-06-13 16:45:54 -04:00
Bruno Martins	9702b68d72	Remove cache implementation, to be discussed and done later	2019-06-13 11:08:25 -07:00
Bruno Martins	6a163d7fd4	Make Travis happy	2019-06-13 11:08:25 -07:00
Bruno Martins	1832c417e6	Make Travis happy	2019-06-13 11:08:25 -07:00
Bruno Martins	148cfef572	Make Travis happy	2019-06-13 11:08:25 -07:00
Bruno Martins	31050952b6	Validator: add simple Result caching	2019-06-13 11:08:25 -07:00
Bruno Martins	e0d422ffd9	Validator: fix path handling and tests Makefile	2019-06-13 11:08:25 -07:00
Bruno Martins	452f2379a1	Validator: use it in all remaining normative types	2019-06-13 11:08:25 -07:00
Bruno Martins	e2d95128a3	Validator: add some documentation	2019-06-13 11:08:25 -07:00
Bruno Martins	3a178ea5c4	Use Validator API for ntattribute and ntndarrayattribute	2019-06-13 11:08:25 -07:00
Bruno Martins	24489f6535	NTField: remove is<Structure> check from its is* methods	2019-06-13 11:08:25 -07:00
Bruno Martins	28ca7ac1ab	Validator: '{maybe,}has<fn>' becomes {maybe,}has<fn, T=Field> to allow for optional specific type checking	2019-06-13 11:08:25 -07:00
Bruno Martins	5a0b42fec7	Remove leftover 'once' declaration from ntndarray.h	2019-06-13 11:08:25 -07:00
Bruno Martins	35bf9dcb13	Revert changes in NTNDArray's builder: should be part of a separate PR	2019-06-13 11:08:25 -07:00
Bruno Martins	f22b5d5b7b	Completely rework Validator API	2019-06-13 11:08:25 -07:00
Bruno Martins	9923459c4b	Formatting	2019-06-13 11:08:25 -07:00
Bruno Martins	50a7208174	Fix NTNDArray Validator	2019-06-13 11:08:25 -07:00
Bruno Martins	7e7949b1fa	Rework Validator API, allow extra Union fields, add tests	2019-06-13 11:08:25 -07:00
Bruno Martins	76c00b78c9	Make Validator private	2019-06-13 11:08:25 -07:00
Bruno Martins	1676192dd1	Fix ifdef guard for shared symbols	2019-06-13 11:08:25 -07:00
Bruno Martins	b76c91a885	Begin work on general NT validator	2019-06-13 11:08:25 -07:00
Michael Davidsaver	2d186d40d5	remove use of Display.setFormat	2019-05-05 19:42:57 -07:00
Andrew Johnson	e803240fbf	Update SHRLIB_VERSION	2019-03-20 13:57:00 -05:00
Michael Davidsaver	54c07f705f	update docs	2019-03-12 19:45:30 -07:00
Michael Davidsaver	fa23ddd370	NTTable::getColumnNames() wrong field	2019-03-12 17:42:36 -07:00
Andrew Johnson	41d56fdf89	Update version numbers and formatting in documentation	2018-12-17 16:05:45 -06:00
Andrew Johnson	a65fc3ef30	Update and unify README.md	2018-12-17 16:04:09 -06:00
Michael Davidsaver	b69bc44974	5.2.1	2018-11-26 11:52:01 -08:00
Michael Davidsaver	a90f0173a7	drop redundant generated html	2018-11-26 11:50:39 -08:00
Michael Davidsaver	83342beb7e	travis-ci dropped 3.14	2018-10-29 19:42:12 -07:00
Michael Davidsaver	f6e6cf037f	update travis-ci	2018-10-29 17:57:18 -07:00
Andrew Johnson	80920ae0b0	Clean up warnings Removed unused member variables 'bool dim'.	2018-01-04 17:16:34 -06:00
Michael Davidsaver	1f7667b22d	drop prototype PVNTField::createAlarmLimit not implemented.	2017-12-19 17:15:37 -06:00
Ralph Lange	e15e84fb14	jenkins-ci: fix/update CloudBees jobs	2017-12-19 09:58:49 +01:00