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RE: Accepting non-deterministic content models

• From: Nicolas LEHUEN <nicolas.lehuen@u...>
• To: "'vdv@d...'" <vdv@d...>,"'Roger L. Costello'" <costello@m...>
• Date: Mon, 09 Jul 2001 10:31:46 +0200

The schema may be non deterministic, but given a document, it is possible to
tell whether it is valid or not. Back to Roger's question, is it normal that
some schema validators cannot handle grammars with lookahead ?

>-----Message d'origine-----
>De : Eric van der Vlist [mailto:vdv@d...]
>Envoye : vendredi 6 juillet 2001 20:57
>A : Roger L. Costello
>Cc : xml-dev@l...
>Objet : Re: Accepting non-deterministic content models
>
>
>"Roger L. Costello" wrote:
>> 
>> Hi Eric,
>> 
>> Consider this portion of an instance document:
>> 
>> <test>
>>     <a>
>> 
>> When a parser gets to <a>, which "a" is it - the element declaration
>> that is the immediate child of <xsd:choice>, or the element 
>declaration
>> that is an immediate child of <xsd:sequence>?  There's no way for the
>> parser to know unless it "looks ahead" to the next element.  That's
>> non-deterministic.  /Roger
>
>Yes, I get it, but I find it confusing to say that the content model is
>non deterministic.
>
>The content model itself is deterministic, but (and I don't know how to
>say it in one word) it happen to be non deterministic at a 
>point in time
>for parsers that do not look ahead and have a partial view on 
>the schema
>and is therefor considered as invalid by W3C XML Schema ;=) ...
>
>I think it's important to keep in mind what are the limitations of the
>tools we use and what are the conceptual limitations of the "objects"
>that we manipulate.
>
>Thanks for the clear explanation!
>
>Eric
>
>-- 
>See you at XTech in San Diego.
>             
>http://conferences.oreillynet.com/cs/os2001/view>/e_spkr/790
>
>
>---------------------------------------------------------------
>---------
>Eric van der Vlist       http://xmlfr.org            
>http://dyomedea.com
>http://xsltunit.org      http://4xt.org    
>       
>http://examplotron.org
>---------------------------------------------------------------
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