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RE: Multiple and circular import/include

From: Bill Michell <bill.michell@bbc.co.uk>
Date: Thu, 3 Mar 2005 09:32:50 -0000
Message-ID: <865D963E3D4C48419BAF092534B2BB5802CEFBC8@bbcxues07.national.core.bbc.co.uk>
To: "vivek agarwal" <vivekorama@gmail.com>, "Bob Schloss" <rschloss@us.ibm.com>
Cc: <xmlschema-dev@w3.org>

I find them really useful...

I have a generic "asset" that can have many types of extension - but any instance of that asset need to be able to contain other assets - either references, or completely embedded inline.

The core document contains the basic asset definition but the extensions each live in their own schema - that needs a reference to the core document - which in turn needs a reference to the current collection of extension schemae...

In other words elements can be nested recursively so the schema documents need to be able to express that nesting. 



-- 
Bill Michell
Development Team Leader, Broadcast Platforms, BBC News Interactive.



-----Original Message-----
From: xmlschema-dev-request@w3.org [mailto:xmlschema-dev-request@w3.org] On Behalf Of vivek agarwal
Sent: Wednesday, March 02, 2005 9:03 PM
To: Bob Schloss
Cc: xmlschema-dev@w3.org
Subject: Re: Multiple and circular import/include


Thanks Bob!
But, I still don't understand why the spec allows circular references!? Is there a reason? or is it just like that?

Thanks,
Vivek.



On Tue, 1 Mar 2005 15:17:04 -0500, Bob Schloss <rschloss@us.ibm.com> wrote:
> 
> 
> Vivek,
> 
>       It is not an error to include the same schema document as the 
> target of multiple <include> or <import> directives.
> 
>       Circular <include> or <import> directives are permitted.
> 
>       This is my mental model:
> 
> 1. The processor fetches your top-level schema document, and then 
> keeps fetching any other schemas which are referenced through 
> directives, transitively, but whenever it sees a directive targetting 
> something it has already fetched, it doesn't fetch it again.  At the 
> end of this process, the "actual schema" to be used for processing now 
> exists in memory, having been merged from 1...n individual documents 
> having the XML representation of XML Schema.
> 
> 2. Then the processor starts doing whatever it plans to do (validation 
> of instance documents during parsing, generating Data Binding code, 
> generating UI forms, or whatever).
> 
>       Because of subtleties associated with <redefine>, for the sanity 
> of anyone who may have to maintain what you design, I would try to 
> avoid circular redefines.
> 
>             Good Luck,
>             Bob
> 
> Scalable XML Infrastructure
> IBM Thomas J Watson Research Center
> Yorktown Heights, New York, USA
> http://www.research.ibm.com/XML
> 
>              vivek agarwal
>              <vivekorama@gmail
>              .com>                                                      To
>              Sent by:                  xmlschema-dev@w3.org
>              xmlschema-dev-req                                          cc
>              uest@w3.org
>                                                                    Subject
>                                        Multiple and circular
>              03/01/2005 01:41          import/include
>              AM
> 
>              Please respond to
>                vivek agarwal
> 
> 
> Hi,
> 
> I have a question on multiple and circular import/include each, if 
> somebody could help.
> 
> Is it an error to import/include a schema more than once?
> A import/includes B1 and B2.
> Both B1, and B2, import/includes C.
> What is the expected behaviour of the processor in such a case?
> 
> Are circular import/includes allowed?
> A import/includes B, and B import/includes A?
> What is the expected behaviour of the processor in such a case?
> 
> Thanks,
> Vivek.
> 
>


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Received on Thursday, 3 March 2005 11:08:45 GMT

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