diff --git a/src/ntaggregate.cpp b/src/ntaggregate.cpp
index cdd126c..c4deda6 100644
--- 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)
diff --git a/src/ntcontinuum.cpp b/src/ntcontinuum.cpp
index 72c10f4..792217e 100644
--- 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;
diff --git a/src/ntenum.cpp b/src/ntenum.cpp
index bb9bd6c..6ac4f4e 100644
--- 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;
diff --git a/src/nthistogram.cpp b/src/nthistogram.cpp
index 63c02c0..7c0ecdb 100644
--- 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)
diff --git a/src/ntmatrix.cpp b/src/ntmatrix.cpp
index bc2bfd4..090c905 100644
--- 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)
diff --git a/src/ntmultiChannel.cpp b/src/ntmultiChannel.cpp
index 79d258c..c26f641 100644
--- 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;
diff --git a/src/ntnameValue.cpp b/src/ntnameValue.cpp
index 7f250ff..d34d6b9 100644
--- 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)
diff --git a/src/ntscalar.cpp b/src/ntscalar.cpp
index b1685ee..afa4b32 100644
--- 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;
diff --git a/src/ntscalarArray.cpp b/src/ntscalarArray.cpp
index bc748e7..3c82e42 100644
--- 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)
diff --git a/src/ntscalarMultiChannel.cpp b/src/ntscalarMultiChannel.cpp
index 474b337..69d2be7 100644
--- 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;
diff --git a/src/nttable.cpp b/src/nttable.cpp
index b26e0c7..458dd9d 100644
--- 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)
diff --git a/src/ntunion.cpp b/src/ntunion.cpp
index bf055c8..91d5529 100644
--- 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)
diff --git a/src/nturi.cpp b/src/nturi.cpp
index ca1b1f9..9bf9f8f 100644
--- 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();
 }
 
 
diff --git a/src/pv/ntfield.h b/src/pv/ntfield.h
index 7a51e58..e79cf3e 100644
--- a/src/pv/ntfield.h
+++ b/src/pv/ntfield.h
@@ -160,9 +160,21 @@ private:
     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;
 };
 
 /**