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Re: Business rules in schema

From: Paul Warren <pdw@decisionsoft.com>
Date: 23 May 2003 11:26:32 +0100
To: Arvind M Patil <arvind.patil@majoris.com>
Cc: xmlschema-dev@w3.org
Message-Id: <1053685589.11199.637.camel@tobol.dsl.local>

On Fri, 2003-05-23 at 10:03, Arvind M Patil wrote: 
> Can I define a business rules in xml schema definition.
> For example: Consider a sample xml definition
> <employee>
>     <name>xyz</name>
>     <age>30</age>
>     <maxServiceAllowed>28</maxServiceAllowed>
>     <maxAge>58</maxAge>
> </employee>
> So based on this hypothetical information, I wanted to have validation
> rule in schema such away that
> maxServiceAllowed =  maxAge - age
> Can I acheive this in schema? Thanks for attention.

No, is the simple answer.  XML Schema does not provide for this sort of
cross-field validation.  The most common way to implement this is to use
a Schematron [1] schema in addition to an XML Schema.  There is some
discussion of including co-constraints into XML Schema 1.1 [2], but as I
understand it this will be limited, if included at all, and still may
not cover the case above at all.

My company provides XML validation tools, so how to handle rules such as
the above has been a subject of interest to us for some time.  We
recently put together a paper[3] on how additional business rules might
incorporated into XML Schema.  This was more a hypothetical
investigation into how it might work, rather than a real proposal, in
order to drive the future development of our products.

Interestingly, I recently came across a Sun tool [4] that allows
Schematron rules to be integrated with Relax NG schemas in a way that
overcomes some of the problems associated with embedding Schematron
rules into XML Schema.


[1] http://www.ascc.net/xml/resource/schematron/schematron.html
[2] http://www.w3.org/TR/2003/WD-xmlschema-11-req-20030121/#N40011D
[3] http://www.decisionsoft.com/pdw/busRules.pdf
[4] http://wwws.sun.com/software/xml/developers/schematronaddon/
Paul Warren, Client Services           DecisionSoft Limited
+44-1865-203192                        http://www.decisionsoft.com
Received on Friday, 23 May 2003 06:27:28 UTC

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