NXdata: @signal, @auxiliary_signals and @axes refer to direct NXdata …

…children

base_classes/NXdata.nxdl.xml

@@ -53,10 +53,12 @@
 		<doc>
 			.. index:: plotting
 
-			Array of strings holding the names of additional signals to
-			be plotted with the default signal (specified by the
-			``signal`` attribute).  Each auxiliary signal needs to be of
-			the same shape as the default signal.
+			Array of strings holding the :ref:`names &lt;validItemName>` of additional
+			signals to be plotted with the default signal (specified by the
+			``signal`` attribute). These field(s) *must* exist and be direct children
+			of this NXdata group.
+
+			Each auxiliary signal needs to be of the same shape as the default signal.
 
 			..  NIAC2018:
 			    https://www.nexusformat.org/NIAC2018Minutes.html
@@ -69,9 +71,8 @@
 			.. index:: signal attribute value
 
 			Declares which NeXus field is the default. 
-			The value is the name of the NeXus field to be plotted.
-			(The value :ref:`names &lt;validItemName>` an existing child
-			of this group. The child group must itself be a NeXus group.)
+			The value is the :ref:`name &lt;validItemName>` of the data field to be plotted.
+			This field must *exist* and be a direct child of this NXdata group.
 
 			It is recommended (as of NIAC2014) to use this attribute
 			rather than adding a signal attribute to the field.
@@ -89,10 +90,11 @@
 			the ``signal`` attribute of this group). 
 			One entry is provided for every dimension in the *signal* field.
 
-			The field(s) named as values (known as "axes") of this attribute 
-			*must* exist. An axis slice is specified using a field named 
-			``AXISNAME_indices`` as described below (where the text shown here
-			as ``AXISNAME`` is to be replaced by the actual field name).
+			The field(s) :ref:`named &lt;validItemName>` as values (known as "axes")
+			of this attribute *must* exist and be direct children of this NXdata group.
+			An axis slice is specified using a field named ``AXISNAME_indices``
+			as described below (where the text shown here as ``AXISNAME`` is to be
+			replaced by the actual field name).
 
 			When no default axis is available for a particular dimension 
 			of the plottable data, use a "." in that position.