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RE: Redefine and Import used together - is this valid?

From: Michael Kay <mike@saxonica.com>
Date: Fri, 15 Sep 2006 17:38:21 +0100
To: "'Danny Vint'" <dvint@sack.dreamhost.com>, <xmlschema-dev@w3.org>, <xml-dev@lists.xml.org>
Message-ID: <00d001c6d8e5$5be82a10$6601a8c0@turtle>


The rule imposed by XML Schema is that you can't use two different types
with the same name in the same validation episode. So you can't use a type
and its redefinition.

Many products have a schema cache of one kind or another. Whether such a
cache allows you to have more than one type with the same name is very much
implementation-defined, because the spec confines itself to the behaviour of
a single validation episode. Saxon, for example, will prevent you redefining
a type if the base type in the schema cache has already been used for
validation, even in a previous episode.

Michael Kay
http://www.saxonica.com/ 


> -----Original Message-----
> From: xmlschema-dev-request@w3.org 
> [mailto:xmlschema-dev-request@w3.org] On Behalf Of Danny Vint
> Sent: 15 September 2006 16:41
> To: xmlschema-dev@w3.org; xml-dev@lists.xml.org
> Subject: Redefine and Import used together - is this valid?
> 
> 
> I have the following situation:
> 
> 1) Base industry standard schema (ACORD)
> 2) A schema that imports the ACORD schema (to reuse data 
> types and some
> elements) that defines my organizations new elements and 
> aggregates (ACME)
> 3) A schema that redefines #1 ACORD to modify existing 
> elements and aggregates to include my new ACME elements.
> 
> I then have a docuemnt instance the references #3.
> 
> Xerces and XSV say my document and schemas are valid. When I 
> run this with XML Spy I can validate the schemas standalone, 
> but when I try to validate the document based upon the 
> schemas, Spy reports that my redefined elements in #3 have 
> already been defined and this is an error.
> 
> Becasue I knew Spy uses more than one parser (different views 
> use different parsers) I figured the parser valdiating the 
> document was incorrect. Well the Altova folks say their 
> schema validation is wrong in this case. Can I get some 
> confirmation of this one way or another from this group?
> 
> If Altova is correct then I think the Schema working group 
> has some serious work to fix this problem. I'm assuming that 
> I should be able to reuse an industry schema in this manner. 
> We want to both use the same datatypes from ACORD as well in 
> some places to add ACORD elements into our new elements when 
> the definitions are appropriate. If I have to recreate all 
> these types and elements, I loose much of that promise of resuability.
> 
> Any light you can shed on this situation is much appreciated. 
> Meanwhile I'll be tryiing to read the spec on this topic.
> 
> ...dan
> 
> --------------------------------------------------------------
> -------------
> Danny Vint
> 
> Specializing in Panoramic Images of California and the West 
> http://www.dvint.com
> 
> Voice:510:522-4703
> FAX: 801-749-3229
> 
> 
Received on Friday, 15 September 2006 16:38:45 GMT

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