Update NXprocess documentation

base_classes/NXprocess.nxdl.xml

@@ -26,14 +26,25 @@
     xsi:schemaLocation="http://definition.nexusformat.org/nxdl/3.1 ../nxdl.xsd"
     name="NXprocess" 
 	type="group" extends="NXobject">
-    <doc>Document an event of data processing, reconstruction, or analysis for this data.</doc>
+    <doc>
+        The :ref:`NXprocess` class describes an operation used to
+        process data as part of an analysis workflow, providing
+        information such as the software used, the date of the
+        operation, the input parameters, and the resulting data. 
+    </doc>
+    <attribute name="default">
+        <doc>
+            Declares which :ref:`NXdata` group contained within this
+            NXprocess group should be plotted by default.
+        </doc>
+    </attribute>
     <field name="program" type="NX_CHAR">
         <doc>Name of the program used</doc>
     </field>
     <field name="sequence_index" type="NX_POSINT">
         <doc>
-            Sequence index of processing, 
-            for determining the order of multiple **NXprocess** steps.  
+            Sequence index of processing, for determining the order of
+            multiple **NXprocess** steps.  
             Starts with 1.
         </doc>
     </field>
@@ -45,12 +56,22 @@
     </field>
     <group type="NXnote">
         <doc>
-            The note will contain information about how the data was processed
-            or anything about the data provenance. 
-            The contents of the note can be anything that the processing code 
-            can understand, or simple text.
+            The note will contain information about how the data was
+            processed or anything about the data provenance. The
+            contents of the note can be anything that the processing
+            code can understand, or simple text.
 
             The name will be numbered to allow for ordering of steps.
         </doc>
     </group>
+    <group type="NXparameters">
+        <doc>
+            Parameters used in performing the data analysis.
+        </doc>
+    </group>
+    <group type="NXdata">
+        <doc>
+            The data resulting from the operation.
+        </doc>
+    </group>
 </definition>

manual/source/applying-nexus.rst

@@ -561,12 +561,18 @@ Processed Data
    NXprocess
    Processed Data
 
-Data reduction and analysis programs are encouraged to store their results in
-NeXus data files. As far as the necessary, the normal NeXus 
-:index:`hierarchy <hierarchy>`
-is to be implemented. In addition, processed data files
-must contain a :ref:`NXprocess`
-group. This group, that documents and preserves data provenance,
-contains the name of the data processing program and the
-parameters used to run this program in order to achieve the results stored in
-this entry. Multiple processing steps must have a separate entry each.
+Data reduction and analysis programs are encouraged to store their
+results in NeXus data files, which may be the same file that contains
+the raw data. It is recommended to document the actions taken to
+generate the processed data in a :ref:`NXprocess` group, which has
+fields to store the name of the program used, its version number, and
+the date when it was run. If there are multiple processes recorded in
+the file, the group should also contain a sequence index to specify the
+order in which they were run. NXprocess groups can also contain one or
+more :ref:`NXparameters` groups to store the parameters used by the
+program as well as one or more :ref:`NXdata` groups that contain the
+results of the process. This has the advantage of encapsulating all the
+information required to preserve the provenance of the processed data in
+a single group. However, it is also acceptable to store the resulting
+data in a NXdata group at the same level as the NXprocess group in the
+NeXus :index:`hierarchy <hierarchy>`.