diff --git a/devsupApp/src/Makefile b/devsupApp/src/Makefile
index 13aee81..b7993ed 100644
--- a/devsupApp/src/Makefile
+++ b/devsupApp/src/Makefile
@@ -61,6 +61,7 @@ PY += devsup/db.py
 PY += devsup/hooks.py
 PY += devsup/interfaces.py
 PY += devsup/util.py
+PY += devsup/ptable.py
 
 #===========================
 
diff --git a/devsupApp/src/devsup/__init__.py b/devsupApp/src/devsup/__init__.py
index 4eee7ac..977f926 100644
--- a/devsupApp/src/devsup/__init__.py
+++ b/devsupApp/src/devsup/__init__.py
@@ -23,4 +23,6 @@ except ImportError:
     epicsver = (0,0,0,0,"0","")
     pydevver = (0,0)
 
+    INVALID_ALARM = UDF_ALARM = 0
+
 __all__ = []
diff --git a/devsupApp/src/devsup/ptable.py b/devsupApp/src/devsup/ptable.py
new file mode 100644
index 0000000..baa830b
--- /dev/null
+++ b/devsupApp/src/devsup/ptable.py
@@ -0,0 +1,338 @@
+# -*- coding: utf-8 -*-
+
+import logging
+LOG = logging.getLogger(__name__)
+
+import threading
+
+_tables = {}
+
+from devsup.db import IOScanListThread
+from devsup import INVALID_ALARM, UDF_ALARM
+
+__all__ = [
+    'Parameter',
+    'ParameterGroup',
+    'TableBase',
+    'build'
+]
+
+# Reason code to cause a record to read a new value from a table paramter
+_INTERNAL = object()
+
+# action types
+# Default action, call whenever a record associated with the parameter
+# is processed
+_ONPROC = lambda n,o:True
+# Run action when the value of a parameter changes
+_ONCHANGE = lambda n,o:n!=o
+_ISVALID = lambda n,o:n is not None
+_ISNOTVALID = lambda n,o:n is None
+
+def _add_action(self, act, fn):
+    try:
+        L = fn._ptable_action
+    except AttributeError:
+        L = fn._ptable_action = []
+    L.append((self,act,fn))
+    return fn
+
+class Parameter(object):
+    """Define a parameter in a table.
+
+    When a sub-class of TableBase is instancianted, parameters become
+    py:class:`_ParamInstance` instances.
+
+    >>> class MyTable(TableBase):
+        A = Parameter()
+        B = Parameter(name='bb')
+        C = Parameter(iointr=True)
+    >>>
+    
+    Defines a table with three parameters.  The second 'B' defines a different
+    parameter name and attribute name.  The parameter name 'bb' will be used
+    in .db files, which self.B will be used for access from the table instance.
+    
+    When _iointr_ is True, then attached device support may use SCAN='I/O Intr',
+    which is triggered with the method self.B.notify().
+    
+    This class has several methods which may be used decorate member functions
+    as actions when the value of a parameter is (possibly) changed.
+    """
+    def __init__(self, name=None, iointr=False):
+        self.name, self._iointr = name, iointr
+    def onproc(self, fn):
+        """Decorator run a member function action whenever
+        an attached device support processes.
+        
+        >>> class MyTable(TableBase):
+            A = Parameter()
+            @A.onproc
+            def action(self, oldval):
+                print 'A changed from',oldval,'to',self.A.value
+        """
+        return _add_action(self, _ONPROC, fn)
+    def onchange(self, fn):
+        "Decorator to run an action when the value of a parameter is changed."
+        return _add_action(self, _ONCHANGE, fn)
+    def isvalid(self, fn):
+        "Decorator to run an action when the value is valid"
+        return _add_action(self, _ISVALID, fn)
+    def isnotvalid(self, fn):
+        "Decorator to run an action when the value is *not* valid"
+        return _add_action(self, _ISNOTVALID, fn)
+    def oncondition(self, cond):
+        """Decorator which allows a custom condition function to be specified.
+        
+        This function will be invoked with two argument cond(newval,oldval)
+        and is expected to retur a bool.
+        
+        >>> class MyTable(TableBase):
+            A = Parameter()
+            @A.oncondition(lambda n,o:n<5)
+            def action(self, oldval):
+                print self.A.value,'is less than 5'
+        """
+        def decorate(fn, cond=cond, self=self):
+            return _add_action(self, cond, fn)
+        return decorate
+
+class ParameterGroup(object):
+    """A helper for defining actions on groups of parameters
+
+    When a sub-class of TableBase is instancianted, parameter groups become
+    py:class:`_ParamGroupInstance` instances.
+
+    >>> class MyTable(TableBase):
+        A = Parameter()
+        B = Parameter(name='bb')
+        grp = ParameterGroup([A,B])
+    >>>
+
+    This class has several methods which may be used decorate member functions
+    as actions based on the value of parameters in this group.
+    """
+    def __init__(self, params, name=None):
+        self.params, self.name = params, name
+    def onproc(self, fn):
+        """Decorator run a member function action whenever
+        a device support attached to any paramter in the group processes.
+        
+        >>> class MyTable(TableBase):
+            A, B = Parameter(), Parameter()
+            grp = ParameterGroup([A,B])    
+            @grp.onproc
+            def action(self):
+                print self.A.value, self.B.value
+        """
+        return _add_action(self, _ONPROC, fn)
+    def allvalid(self, fn):
+        "Decorator to run an action when all parameters have valid values"
+        return _add_action(self, (all, lambda p:p.isvalid), fn)
+    def anynotvalid(self, fn):
+        "Decorator to run an action when any parameters has an invalid value"
+        return _add_action(self, (any, lambda p:not p.isvalid), fn)
+    def oncondition(self, fmap, freduce=all):
+        """Decorator for a custom condtion.
+        
+        The condition is specified in two parts, a map function, and a reduce function.
+        The map function is applied to each parameter in the group.  Then a list
+        of the results is passed to the reduce function.  If not specified,
+        the default reducing function is all (map func must return bool).
+        
+        >>> class MyTable(TableBase):
+            A, B = Parameter(), Parameter()
+            grp = ParameterGroup([A,B])    
+            @grp.oncondition(lambda v:v>5, any)
+            def action(self):
+                # either A or B is greater than 5
+                print self.A.value, self.B.value
+        """
+        def decorate(fn, fmap=fmap, freduce=freduce, self=self):
+            return _add_action(self, (freduce, fmap), fn)
+        return decorate
+
+class _ParamInstance(object):
+    """Access to a parameter at runtime.
+    """
+    def __init__(self, table, name, scan):
+        self.name = name
+        self.table, self.scan, self._value = table, scan, None
+        self.alarm, self.actions = 0, []
+        self._groups = set()
+    def _get_value(self):
+        return self._value
+    def _set_value(self, val):
+        self._value = val
+        self.alarm = 3 if val is None else 0
+    value = property(_get_value, _set_value, doc="The current parameter value")
+    @property
+    def isvalid(self):
+        """Is the parameter value valid (not None and no INVALID_ALARM)
+        """
+        return self.alarm < INVALID_ALARM and self._value is not None
+    def notify(self):
+        """Notify attached records of parameter value change.
+        A no-op unless Parameter(iointr=True)
+        """
+        if self.scan:
+            self.scan.interrupt(_INTERNAL)
+    def addAction(self, fn, cond=None):
+        """Add an arbitrary action at runtime
+        """
+        self.actions.append((cond, fn))
+    def _exec(self, oldval=None):
+        for C, F in self.actions:
+            if C(self.value, oldval):
+                F()
+
+class _ParamGroupInstance(object):
+    """Runtime access to a group of parameters.
+    """
+    def __init__(self, table, name):
+        self.table, self.name = table, name
+        self.actions, self._params = [], None
+    def __iter__(self):
+        "Iterate over all parameter instances in this group"
+        return iter(self._params)
+    def addAction(self, fn, fmap, freduce=all):
+        "Add an arbitrary action at runtime"
+        self.actions.append((fmap, freduce, fn))
+    def _exec(self):
+        for M, R, F in self.actions:
+            if R(map(M, self._params)):
+                F()
+    def allValid(self):
+        "Quick test if all parameters are valid"
+        for P in self._params:
+            if not P.isvalid:
+                return False
+        return True
+
+class _ParamSup(object):
+    def __init__(self, inst, rec, info):
+        self.inst, self.info = inst, info
+        # Determine which field to use to store the value
+        fname = rec.info('pyfield','VAL')
+        self.raw = fname!='RVAL'
+        self.vfld = rec.field(fname)
+        self.vdata = None
+        if len(self.vfld)>1:
+            self.vdata = self.vfld.getarray()
+    def detach(self, rec):
+        pass
+    def allowScan(self, rec):
+        if self.inst.scan:
+            return self.inst.scan.add(rec)
+    def process(self, rec, reason=None):
+        with self.inst.table.lock:
+            if reason is _INTERNAL:
+                # sync table to record
+                self.inst.table.log.debug('-> %s (%s)', rec.NAME, self.inst.value)
+                nval = self.inst.value
+                if nval is not None:
+                    if self.vdata is None:
+                        self.vfld.putval(nval)
+                    else:
+                        if len(nval)>len(self.vdata):
+                            nval = nval[:len(self.vdata)]
+                        self.vdata[:len(nval)] = nval
+                        self.vfld.putarraylen(len(nval))
+                    if self.inst.alarm:
+                        rec.setSevr(self.inst.alarm)
+                else:
+                    # undefined value
+                    rec.setSevr(INVALID_ALARM, UDF_ALARM)
+
+            else:
+                # sync record to table
+                self.inst.table.log.debug('<- %s (%s)', rec.NAME, rec.VAL)
+                if self.vdata is None:
+                    nval = self.vfld.getval()
+                else:
+                    # A copy is made which can be used without locking the record
+                    nval = self.vdata[:self.vfld.getarraylen()].copy()
+                
+                oval, self.inst.value = self.inst.value, nval
+                
+                # Execute actions
+                self.inst._exec(oval)
+                for G in self.inst._groups:
+                    G._exec()
+
+class TableBase(object):
+    """Base class for all parameter tables.
+    
+    Sub-class this and populate with :py:class:`Parameter` and  :py:class:`ParameterGroup`.
+    
+    When a table is instanciated it must be given a unique name.
+    
+    >>> class MyTable(TableBase):
+        ...
+    >>> x=MyTable(name='xyz')
+    >>>
+    """
+    log = LOG
+    ParamSupport = _ParamSup
+    def __init__(self, **kws):
+        self.name = kws.pop('name')
+        if self.name in _tables:
+            raise KeyError("Table named '%s' already exists"%self.name)
+        self.lock = threading.Lock()
+        self._parameters = {}
+
+        # Find Parameters and ParameterGroup in the class dictionary
+        # and place approprate things in the instance dictionary
+        rparams = {}
+        rgroups = {}
+        for k,v in self.__class__.__dict__.items():
+            if isinstance(v, Parameter):
+                scan = None
+                if not v.name:
+                    v.name = k
+                if v._iointr:
+                    scan = IOScanListThread()
+                P = _ParamInstance(self, v.name, scan)
+                self._parameters[v.name] = P
+                rparams[v] = P
+                setattr(self, k, P)
+            elif isinstance(v, ParameterGroup):
+                if not v.name:
+                    v.name = k
+                G = _ParamGroupInstance(self, v.name)
+                rgroups[v] = G
+                setattr(self, k, G)
+
+        # Populate groups with parameters
+        for g,G in rgroups.iteritems():
+            ps = G._params = [rparams[v] for v in g.params]
+            # reverse mapping from parameter to group(s)
+            for P in ps:
+                P._groups.add(G)
+
+        # second pass to attach actions
+        for k,v in self.__class__.__dict__.items():
+            if hasattr(v, '_ptable_action'):
+                for src,cond,cmeth in v._ptable_action:
+                    # src is instance parameter or group
+                    # cond is a callable for parameters, or a tuple for groups
+                    # cmeth is the unbound method which is the action to take
+                    if isinstance(src, Parameter):
+                        P = rparams[src]
+                        P.addAction(cmeth.__get__(self), cond)
+                    elif isinstance(src, ParameterGroup):
+                        G = rgroups[src]
+                        G.addAction(cmeth.__get__(self), cond[1], cond[0])
+
+        super(TableBase, self).__init__(**kws)
+        self.log.info("Initialized ptable '%s'",self.name)
+        _tables[self.name] = self
+
+def build(rec, args):
+    parts = args.split(None,2)
+    table, param = parts[:2]
+    info = None if len(parts)<3 else parts[2]
+    T = _tables[table]
+    P = T._parameters[param]
+    T.log.debug("Attaching ptable '%s, %s' to %s", T.name, P.name, rec.NAME)
+    return T.ParamSupport(P, rec, info)
diff --git a/documentation/index.rst b/documentation/index.rst
index d7d1270..41109f2 100644
--- a/documentation/index.rst
+++ b/documentation/index.rst
@@ -18,7 +18,7 @@ Contents:
    environment
    devsup
    interfaces
-
+   ptable
 
 Indices and tables
 ==================
diff --git a/documentation/ptable.rst b/documentation/ptable.rst
new file mode 100644
index 0000000..d5f1e70
--- /dev/null
+++ b/documentation/ptable.rst
@@ -0,0 +1,42 @@
+ptable Package
+==============
+
+.. module:: devsup.ptable
+
+The :py:mod:`devsup.ptable` module provides the means to define a Parameter Table,
+which is something like a dictionary (parameter name <-> dict key)
+where a parameter may be associated (attached) with zero or more EPICS records.
+
+Changes to a parameter may be reflected in the attached records.
+A change in an attached record will update the parameter value,
+and optionally, involve some functions (actions) to make some use of the new value.
+
+The basis of all tables is the :py:class:`TableBase` class.  User code
+will typically sub-class :py:class:`TableBase`.
+
+Defining Parameters
+^^^^^^^^^^^^^^^^^^^
+
+.. autoclass:: Parameter
+    :members:
+
+.. autoclass:: ParameterGroup
+    :members:
+
+.. autoclass:: TableBase
+    :members:
+
+Runtime Access
+^^^^^^^^^^^^^^
+
+.. autoclass :: _ParamInstance
+    :members:
+
+.. autoclass :: _ParamGroupInstance
+    :members:
+
+Device Support
+^^^^^^^^^^^^^^
+
+A general purpose device support is provided to access table parameters.
+The input/output link format is "@devsup.ptable <tablename> <param> [optional]"
diff --git a/test.cmd b/test.cmd
index 7acc036..4335911 100644
--- a/test.cmd
+++ b/test.cmd
@@ -3,6 +3,9 @@
 dbLoadDatabase("dbd/softIocPy.dbd")
 softIocPy_registerRecordDeviceDriver(pdbbase)
 
+py "import logging"
+py "logging.basicConfig(level=logging.DEBUG)"
+
 py "import devsup; print devsup.HAVE_DBAPI"
 py "import sys; sys.path.insert(0,'${PWD}/testApp')"
 py "print sys.path"
@@ -14,6 +17,10 @@ py "import test2"
 py "test2.addDrv('AAAA')"
 py "test2.addDrv('BBBB')"
 
+py "import test6"
+py "test6.SumTable(name='tsum')"
+
 dbLoadRecords("db/test.db","P=md:")
+dbLoadRecords("db/test6.db","P=tst:,TNAME=tsum")
 
 iocInit()
diff --git a/testApp/Makefile b/testApp/Makefile
index 0fe6214..422f250 100644
--- a/testApp/Makefile
+++ b/testApp/Makefile
@@ -11,6 +11,7 @@ include $(TOP)/configure/CONFIG
 # Create and install (or just install) into <top>/db
 # databases, templates, substitutions like this
 DB += test.db
+DB += test6.db
 
 #----------------------------------------------------
 # If <anyname>.db template is not named <anyname>*.template add
diff --git a/testApp/test6.db b/testApp/test6.db
new file mode 100644
index 0000000..3517bb3
--- /dev/null
+++ b/testApp/test6.db
@@ -0,0 +1,22 @@
+record(ao, "$(P):A") {
+  field(DTYP, "Python Device")
+  field(OUT , "@devsup.ptable $(TNAME) A")
+}
+
+record(ao, "$(P):B") {
+  field(DTYP, "Python Device")
+  field(OUT , "@devsup.ptable $(TNAME) B")
+}
+
+record(ao, "$(P):C") {
+  field(DTYP, "Python Device")
+  field(OUT , "@$(TNAME) C")
+  info("pySupportMod", "devsup.ptable")
+}
+
+record(ai, "$(P):S") {
+  field(DTYP, "Python Device")
+  field(INP , "@devsup.ptable $(TNAME) S")
+  field(SCAN, "I/O Intr")
+  field(PINI, "YES")
+}
diff --git a/testApp/test6.py b/testApp/test6.py
new file mode 100644
index 0000000..81ad4f3
--- /dev/null
+++ b/testApp/test6.py
@@ -0,0 +1,34 @@
+# -*- coding: utf-8 -*-
+
+import logging
+LOG = logging.getLogger(__name__)
+
+import devsup.ptable as PT
+
+class SumTable(PT.TableBase):
+    A = PT.Parameter()
+    B = PT.Parameter()
+    C = PT.Parameter()
+    S = PT.Parameter(iointr=True)
+    
+    inputs = PT.ParameterGroup([A,B])
+
+    @C.onchange
+    def newC(self):
+        LOG.debug("C is %s", self.C.value)
+
+    @inputs.anynotvalid
+    def inval(self):
+        print self.A.isvalid, self.B.isvalid
+        LOG.debug("%s.update inputs not valid", self.name)
+        self.S.value = None
+        self.S.notify()
+
+    @inputs.allvalid
+    def update(self):
+        if not all(map(lambda P:P.isvalid, [self.A, self.B])):
+            self.inval()
+            return
+        self.S.value = self.A.value + self.B.value
+        LOG.debug("%s.S = %s", self.name, self.S.value)
+        self.S.notify()