[NeXus-tech] continuing progress on nxdl2xsd.xsl

[Pete Jemian]

nxdl2xsd.xsl is the XSLT translator to convert our NXDL definitions into 
XML Schema.  Each NXDL will result in a new XML Schema complexType based 
on the instructions given.

Status: nxdl2xsd.xsl is working (generates valid XSD, can include 
multiple of these together) but still needs some more development before 
we can validate NeXus data files using the derived XML Schema files.  
Now, I am trying to generate simple and valid test files based on these 
rules (for comparison with existing NeXus files).  Also, the 
nxdl2xsd.xsl code is a bit complicated and might be hard to modify.


When it comes to NXDL groups, we need a special rule that looks like 
this in the XSLT:

           <xsl:attribute name="name">
               <xsl:choose>
                   <!-- @name was specified, use it (to avoid multiple 
elements with same name) -->
                   <xsl:when test="count(@name)>0"><xsl:value-of 
select="@name"/></xsl:when>
                   <!-- default -->
                   <xsl:otherwise><xsl:value-of 
select="@type"/></xsl:otherwise>
               </xsl:choose>
           </xsl:attribute>

This chooses the name attribute in a class's XML schema (such as 
NXsample.xsd) based on what is found in the NXDL group declarations.  If 
a name attribute is given in the NXDL for a group, then use it as the 
name attribute in the translated XSD file.  Default is to get name from 
the NXDL type attribute.

for example, these two NXDL lines:
   <group name="other_notes" type="NXnote"/>
   <group type="NXcharacterization" />
will translate to these XML Schema lines
     <xs:element name="other_notes" minOccurs="0" maxOccurs="unbounded" 
type="nx:NXnote"/>
     <xs:element name="NXcharacterization" minOccurs="0" 
maxOccurs="unbounded" type="nx:NXcharacterization"/>

This type of rule is needed to avoid having duplicate name errors 
(Unique Particle Attribution violations) in the XML Schema files.  
Problems that cropped up were multiple NXlog entries with the same name 
in NXsample or multiple NXnote entries in NXentry and NXdetector and 
perhaps other similar instances.  (This also looks like the intent of 
the name attribute in the NXDL group declaration and the metaDTD.)

Also, I'm wrestling with namespace declarations to simplify the header 
in the NeXus XML data files.  I expect the NeXus XML data file to look 
something like this:

<?xml version="1.0" encoding="UTF-8"?>
<!-- some comments or reference to style sheet may appear here -->
<NXroot
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://definition.nexusformat.org/schema/3.1 
NeXus.xsd"
    xmlns="http://definition.nexusformat.org/schema/3.1">
  <NXentry>
<!-- file content here -->
  </NXentry>
  <NXentry><!-- as desired --></NXentry>
</NXroot>


Pete


-- 
----------------------------------------------------------
  Pete R. Jemian, Ph.D.                <jemian at anl.gov>
  Beam line Controls and Data Acquisition, Group Leader
  Advanced Photon Source,   Argonne National Laboratory
  Argonne, IL  60439                   630 - 252 - 3189
-----------------------------------------------------------
     Education is the one thing for which people
        are willing to pay yet not receive.
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