RE: Streaming Validation

To put Noah's answer in a little perspective, at the London f2f
key/keyref/unique were constrained to use a very reduced subset of XPath
which can be implemented in a manner similar to ID/IDREF and which supports
streaming.

Matthew

> -----Original Message-----
> From: Noah_Mendelsohn@lotus.com [mailto:Noah_Mendelsohn@lotus.com]
> Sent: Wednesday, February 07, 2001 8:07 AM
> To: Charles Reitzel
> Cc: www-xml-schema-comments@w3.org
> Subject: Re: Streaming Validation
> 
> 
> Streaming was considered in great detail, and while not a formal 
> requirement, we have tried to be very sensitive to the needs.  For 
> example, if you look carefully at the rules for accessing 
> schema documents 
> they were carefully crafted to allow streaming processors to 
> incrementally 
> discover which namespaces (and hence schemas) are involved, 
> and to produce 
> results identical to those of a non-streaming processor.
> 
> You are correct, ID/IDREF and key/keyref/unique are the big 
> challenges. 
> The former is just carrying over an XML 1.0 feature and 
> restating it.  The 
> latter is similar but more powerful.  I think you will see 
> some changes 
> that make key/keyref/unique a bit less challenging, but in 
> general there 
> is no magic.  You need to keep look-aside tables of any 
> information that 
> might be needed for alter reference (which in almost all 
> cases is far less 
> than the contents of an entire DOM....in the case of ID/IDREF 
> you just 
> need to keep the pertinent attribute values (I think that's 
> all ID values, 
> and any IDREFs that have not yet validated.)  Similar 
> approaches apply to 
> key/keyref/unique:  the amount you have to keep is roughly 
> proportional to 
> the union of keyvalues and keyref values. 
> 
> So, these issues have been considered, and you will indeed be 
> able to use 
> SAX, in my opinion.  It is true that certain validation 
> results cannot be 
> known at the time the corresponding construct is parsed, but 
> that's true 
> of XML 1.0 IDREFs anyway.
> 
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> Noah Mendelsohn                                    Voice: 
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> Lotus Development Corp.                            Fax: 1-617-693-8676
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Received on Wednesday, 7 February 2001 13:48:17 UTC