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   RE: [xml-dev] Fast Infoset: does the name fit?

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> -----Original Message-----
> From: Elliotte Rusty Harold [mailto:elharo@metalab.unc.edu] 
> Sent: Saturday, April 09, 2005 08:26
> To: xml-dev
> Subject: [xml-dev] Fast Infoset: does the name fit?
> Question for the Sun folks:


Fast Infoset and Fast Web Services are not a Sun thing.  They are two standards being developed by a joint ITU-T / ISO / IEC committee.   A great effort has been put into this work both by Sun and by other members of the committee (such as my company, OSS Nokalva).

Both ISO/IEC 28424-1 (Fast Infoset) and ISO/IEC 28242-2 (Fast Web Services) have successfully completed the FCD ballot in ISO.  The corresponding ITU-T Recommendations are named X.891 and X.892 respectively and are progressing in the ITU-T.

> You've been careful to call your binary format "Fast Infoset" and not 
> use the word XML. That's better. However, what about the word 
> "Infoset"? 
> Is FI a faithful representation of the XML Infoset? 

FI is capable of faithfully representing any infoset that can be represented as a namespace-well-formed XML 1.0 document.

In other words, there are some infosets that cannot be represented, but those are ones which would not be representable in XML 1.0 either, at least not as namespace-well-formed documents.  Here is an example:

The [namespace name] property of each element information item together with the [namespace attributes] property of all element information items and the [prefix] property of that element information item form an XML-self-consistent set;


The term "XML-self-consistent" is used in this clause with the following meaning: a set properties of one or more information items is "XML-self-consistent" if that set of properties could have been obtained by parsing a suitable namespace-well-formed XML document.

> In particular,
> 1. Does FI refuse to encode XML documents that do not have 
> well-defined 
> infosets? 

FI does not encode XML documents.  It encodes XML infosets.

If you start from an infoset (rather than from an XML document), the FI document will faithfully represent your infoset.

If you start from an XML document, you will need to extract the infoset from it first.  Then the FI document will faithfully represent that infoset.

> For instance, does it disallow relative namespace 
> URIs? 

It disallows everything that the XML Infoset recommendation disallows.  In addition, it disallows anything (in the infoset) that would make it impossible to serialize the infoset into an XML 1.0 document or would make the resulting XML 1.0 document non-namespace-well-formed.

> Does 
> every FI have a well-defined XML infoset?

The XML infoset of a FI document is the XML infoset that the FI document encodes.

> 2. Can FI represent infosets that do not have equivalent XML 
> serializations? 


> For instance, infosets in which the in-scope 
> namespaces 
> property is inconsistent with the namespace attributes property?


Alessandro Triglia
OSS Nokalva

> -- 
> Elliotte Rusty Harold  elharo@metalab.unc.edu
> XML in a Nutshell 3rd Edition Just Published!
> http://www.cafeconleche.org/books/xian3/
> http://www.amazon.com/exec/obidos/ISBN=0596007647/cafeaulaitA/

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