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UBL

• To: xml-dev@l...
• Subject: UBL
• From: Dave Scott <dms@h...>
• Date: Thu, 16 Mar 2006 21:46:37 -0600
• Reply-to: xml-dev@l...

I was curious about opinions and experiences people on the list might  
have regarding the UBL NDR:

-  Am I alone in finding it too be overly draconian?
-  What practical limitations (particularly processing limitations)  
have you encountered when implementing the standard?

Perhaps my biggest problem with the NDR  is the prohibition against  
custom attributes.  I'm contributing to a workgroup to develop a data  
standard which will be used to transmit potentially huge data sets.   
Understandably, we'd like the standard to be friendly to stream  
processing.  The ability to add "type" and "role" attributes in key  
places in the schema would greatly aid processing the data in a way  
that would only require examining the current element stack during  
stream processing for our most typical use cases.  The UBL proponents  
on the workgroup propose requiring such items to be a first child  
(rather than attribute) of the node they qualify so as to act as a  
processing flag for its siblings and siblings' children.

My problem with this approach is that if an element has a scoping  
relationship to the rest of the children of the parent, if at all  
possible, I believe you should make that relation explicit by making  
it an atttribute of the parent.  Also, I believe you shouldn't  add  
ordering constraints to your schema, burdening both the production  
and validation of the data set, unless there is a semantic  
motivation.  Lastly, I believe that if at all possible you should  
design the schema to be compatible with the widest range of generic  
tools (e.g., tools that only consider the current ancestor hierarchy  
during stream processing, like STX) rather than requiring future  
users of the standard to write one-off processors (e.g., custom SAX  
handlers.)

A couple of key individuals on the workgroup are adamant about  
adhering to the UBL NDR (although not very articulate when it comes  
to justifying either the individual requirements of the NDR or the  
blanket decision to follow it slavishly.)  Unfortunately, the  
literature I've been able to turn up regarding the UBL NDR all reads  
like marketing literature rather than frank evaluations of the trade- 
offs the NDR involves. (My best source has been the UBL mail archives  
but it's fragmented and skimpy on this topic.)  Can anyone point me  
to some more thoughtful evaluations of the NDR?  Or, perhaps,  
implementations of CCTS that allow custom attributes?  Or, better  
yet, UBL endorsed mechanisms for integrating custom attributes with  
otherwise UBL NDR compliant schema?

Dave

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    • From: "bryan rasmussen" <rasmussen.bryan@g...>

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