RE: [xml-dev] Does DTD allow deriving all possible paths in anXMLdocumen

[ycao5@scs.carleton.ca]

Dear Michael, Liam and Bjoern,


      Thank you all. I appreciate your explanation.

Regards,

Yang



Quoting Michael Kay <mike@saxonica.com>:

> One other point: you need to know what the root element type is. Technically
> this is not part of the document type definition (=DTD), rather it is part
> of the document type declaration. The two are often (understandably)
> confused.
>
> Regards,
>
> Michael Kay
> http://www.saxonica.com/
> http://twitter.com/michaelhkay
>
>
>> -----Original Message-----
>> From: Liam Quin [mailto:liam@w3.org]
>> Sent: 13 October 2009 01:04
>> To: ycao5@scs.carleton.ca
>> Cc: xml-dev@lists.xml.org
>> Subject: Re: [xml-dev] Does DTD allow deriving all possible
>> paths in an XMLdocument?
>>
>> On Mon, Oct 12, 2009 at 07:10:26PM -0400, ycao5@scs.carleton.ca wrote:
>> >     I have one question about XML DTD. In a paper, the authors say
>> > that DTD allows deriving all possible paths from the root to the
>> > leaves appearing in related XML documents. Does this statement
>> > correct? Based on my knowledge, DTD may not contain all possible
>> > elements in an XML document. I would like to get your
>> opinion. Thanks.
>>
>> If you say that the XML document must be dtd-valid, then all
>> elements in the document must be listed (and defined) in the DTD.
>>
>> A ontent model like
>> <!ELEMENT mayhem ANY>
>> means that "mayhem" elements may contain any elements at all
>> as children (as well as text), but for the document to be
>> valid the elemets must still be declared.
>>
>> However, it is not possible to precompute all paths to leaves, because
>> (1) mayhem could have any elements as children
>> (2) a recursive content content model does not generate a finite
>>     grammar - there's an unbounded set of possible valid input
>>     documents.
>>
>> e.g. <!ELEMENT doll (doll?)>
>> allows
>>     <doll><doll><doll /></doll></doll>
>> to any depth.
>>
>> These two points, ANY and cursion, are also rtue for SGML.
>>
>> Liam
>>
>>
>> --
>> Liam Quin, W3C XML Activity Lead,
>> http://www.w3.org/People/Quin/ http://www.holoweb.net/~liam/
>> * http://www.fromoldbooks.org/
>>
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