Should we defer loading schema grammars? (Bug 10433)

[sa...@ca.ibm.com]

Hi all,

A while ago we decided to defer the loading of schema grammars, until such
grammar is actually referenced by the instance document. This seemed to be
a good idea, but bug 10433 made me think more.

In the example attached to that bug (option 1), schema document B imports
A; the instance document has an xsi:schemaLocation for B; and the root
element is from namespace A. This is a perfectly valid document, but Xerces
reports an error saying "can't find declaration for the root element".

The reason is that we defer the loading of B, hence grammar A is not loaded
either.

Is there a solution to this while still deferring the loading of schema
grammars? Or do we have to abandon this idea?

Cheers,
Sandy Gao
Software Developer, IBM Canada
(1-905) 413-3255
sandygao@ca.ibm.com


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Schema Annotation

[Bob Master <bo...@yahoo.com>]

Hi

Xerces 2.0.2 has added classes for Annotations, but
the code to parse the Annotations in Schema Parsing is
missing. We are really loking forward to Annotation
support. 

Questions:

- Would it be possible to parse the Annotations when
the grammar is parsed to avoid having to parse the
annotations in PSVI repitetively? 

- When is the Annotation support expected?

thanks
bob


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Re: Should we defer loading schema grammars? (Bug 10433)

[Curt Arnold <ca...@houston.rr.com>]

sandygao@ca.ibm.com wrote:

>Hi all,
>
>A while ago we decided to defer the loading of schema grammars, until such
>grammar is actually referenced by the instance document. This seemed to be
>a good idea, but bug 10433 made me think more.
>
>In the example attached to that bug (option 1), schema document B imports
>A; the instance document has an xsi:schemaLocation for B; and the root
>element is from namespace A. This is a perfectly valid document, but Xerces
>reports an error saying "can't find declaration for the root element".
>
>The reason is that we defer the loading of B, hence grammar A is not loaded
>either.
>
>Is there a solution to this while still deferring the loading of schema
>grammars? Or do we have to abandon this idea?
>  
>
I don't think that bug 10433 is a bug, but is a usage error (or 
unreasonable expectation).  However, you could make Xerces-J recover 
gracefully from that without significantly reworking schema loading.

What you are faced with is a bad hint.  The document author could have 
provided an xsi:schemaLocation="http://www.example.org/namespaceA 
http://www.example.org/schemaB.xsd" or
xsi:schemaLocation="http://www.example.org/namespaceA 
http://www.example.org/schemaB.xsd http://www.example.org/namespaceB 
http://www.example.org/schemaB.xsd".  Either of those hint should have 
allowed to make the connection between an element in namespace A with 
its definition via import (and potential redefinition or extension of 
substitution groups) in schemaB even though schemaB.xsd target namespace 
would have been namespaceB.

So, the question becomes what should the parse do if there are no 
matches for a namespace in the in-scope schema locations?  You could 
have a fallback that if there is no match on the namespace but there are 
in-scope schemaLocations, that you load them (all?) before giving up.



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