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Changing "substitutionGroup" to "choice" and maintaining the validation equality of the schema

From: Marko Smiljanic <m.smiljanic@utwente.nl>
Date: Wed, 15 Oct 2003 19:05:09 +0200
To: <xmlschema-dev@w3.org>
Message-ID: <000f01c3933e$7d745fe0$240b5982@dynamic.cs.utwente.nl>


This is a question concerned with the property of "validation equality"
between the schemas using "substitutionGroup"s and schemas using a
"choice" compositor as a replacement for a substitutionGroup.

The term "validation equality" between different schemas means that the
sets of XML documents that can be validated by those different schemas
are equal.

Now, a short intro and then a question.

*** The Short Intro (written in XSD-like language)...

Lets have Schema 1 defined as:

 element A (abstract=true)
 element B (substitutionGroup="A")
 element C (substitutionGroup="A")
 element D () - sequence - element (ref="A")

Now I convert Schema 1 to a "validation equal" Schema 2, presented

 element B ()
 element C ()
 element D () - sequence - choice -- element (ref="B")
                                  \_ element (ref="C")

What I did is, replaced a reference to an abstract element "A" with a
choice compositor, and then nest all the possible substitutions for "A"
within this choice. I also removed element A as it is defined as
abstract, otherwise, I would add it under the choice too.

*** The question

Do you think/know that it is possible to transform every XML schema
having substitutionGroups using the "choice" trick above, and get the
"validation equal" schema?

Marko Smiljanic

ps. FYI I'm defining a graph-like model for XML schema needed in my
research. The trick above would be a nice workaround to represent
substitution groups in the model using "choice" that is already
supported by the model.

Research assistant, Database Technology
Department of Computer Science, University of Twente 
P.O. Box 217, 7500 AE Enschede, The Netherlands
Phone +31 (053) 489 4520, Fax ~ 2927
E-mail: m.smiljanic@utwente.nl
WWW: www.cs.utwente.nl/~markosm
Received on Wednesday, 15 October 2003 13:06:48 UTC

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