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RE: Streaming Validation

From: Charles Reitzel <creitzel@mediaone.net>
Date: Thu, 8 Feb 2001 22:59:08 -0500 (EST)
Message-Id: <200102090359.f193x8S29517@chmls05.mediaone.net>
To: "Fuchs, Matthew" <matthew.fuchs@commerceone.com>, "'Noah_Mendelsohn@lotus.com'" <Noah_Mendelsohn@lotus.com>
Cc: www-xml-schema-comments@w3.org
Thanks for the responses.  They are reassuring.  Are any non-DOM based
schema validators available (or under development)?

At 10:47 AM 2/7/01 -0800, Fuchs, Matthew wrote:
>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.
>> 
>> --------------------------------------------------------------
>> ----------
>> Noah Mendelsohn                                    Voice: 
>> 1-617-693-4036
>> Lotus Development Corp.                            Fax: 1-617-693-8676
>> One Rogers Street
>> Cambridge, MA 02142
>> --------------------------------------------------------------
>> ----------
>> 
>> 
>> 
>
Received on Thursday, 8 February 2001 22:59:13 GMT

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