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RE: [xml-dev] Schema based XML compare

Diff is difficult.   I'm not to even start down that train.  I think adding schema level *compare* into a comercial diff product wouldn’t be too hard … (ha ! famous last words).

But straight yes/no compare (maybe outputting the offending element) … By "shouldn’t be too hard" I mean in the project I'm working on right now I am 90% of the way there having already figured out how to use the Apache

Schema parser walk through type trees , and already having a StAX based compare engine so I have code lying-around I could misuse to this purpose.    


I think I might work on this  a bit,  see if I can get even  numeric values to compare as data as opposed to text … that would prove/disprove the concept atleast.




David A. Lee




From: Kiel, Paul (LNG-RDU) [mailto:Paul.kiel@lexisnexis.com]
Sent: Thursday, December 23, 2010 9:30 AM
To: David Lee; xml-dev@lists.xml.org
Subject: RE: [xml-dev] Schema based XML compare


Hi David,


As someone who has been working with large libraries of schemas for many years, this tool would be *wonderful*.  I tried down this path myself but there weren’t enough hours in the night.  “Shouldn’t be too hard” must mean you have smaller ambitions that I had wanted.  I knew it would be hard, or at least time consuming maybe is more accurate.

A data model diff would be very useful for doing things like evaluating backward compatibility of libraries of schemas as well as provide some educational material to implementers who need to see how the model has changed since the last release. 


If you find this animal, please do let me know.  If you want to talk offline, I’d be happy to compare notes.


-- Paul



W. Paul Kiel


Consulting Content Engineer

LexisNexis, Global Content Architecture





From: David Lee [mailto:dlee@calldei.com]
Sent: Thursday, December 23, 2010 7:29 AM
To: xml-dev@lists.xml.org
Subject: [xml-dev] Schema based XML compare


I've run into an age-old issue but I don’t see any off-the-shelf solutions for.


Suppose I have 2 XML documents I want to compare (not diff, just give me yes/no are they equivalent).

This is pretty simple to do even with things like ignoring whitespace options etc.  Many tools out there, including one I wrote

( http://www.xmlsh.org/CommandXcmp)


Now here's the twist …


Suppose I want to compare for XSD  data model equivalence, not XDM  equivalence ?








Without type annotation these are different.
But if I declare the type for number to  be xs:double

they should compare equal.


Thus a compare tool should be able to be given a schema and do a comparison and report that these 2 documents are equivalent at the XSD data model level.


Has anyone seen anything like this ?

Would anyone have a use for it ? (I may end up writing it for my own uses).


Not sure how far one can take this before entering murky waters …

Even in the numeric cases there are edge cases where comparisons are not well defined (rounding/precision issues on floating point numbers).

Then add in things like date/times …

But suppose I'm willing to avoid the murky edges and just stick to the obvious cases … shouldn’t be too hard right ?
In fact I suspect its so obvious its been done but I can't find one anywhere.










David A. Lee




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