xml-dev - Re: Why the Infoset?

[Jonathan Borden <jborden@mediaone.net>]

John Cowan wrote:

> Jonathan Borden wrote:
>
> > But it is not hard to describe, that is my point. The XML 1.0 production
> > rules create a parse tree which exactly describes the source document,
down
> > to the byte. This is what I would call the XML property set, and from
this
> > one can subset to one's desire.
>
> Okay, I understand now.  Actually the production-rule level is *not* the
> bottom parsing level, because for the most part PE-references have already
> been removed.

I new there was a reason why you got this job :-)

PE-Reference is production [69] so it can be represented in a production
rule tree, the issue is that the elementDecl tree cannot be built until the
PE-Reference is expanded.

I would handle this as an <alt> with both the PE-Reference and following
character content, and its expanded form side by side.

e.g.

<PEDecl p="72">
    <seq>
        <S><c char=" "/></S>
        <Name>element</Name>
        <S><c char=" "/></S>
        <EntityDef><string value="<!ELEMENT" /></EntityDef>
     </seq>
</PEDecl>

and

<alt>
 <seq>
   <PEReference><Name>element</Name></PEReference>
   <S char=" "/><string value="FOO EMPTY>" />
  </seq>
 <elementDecl>
    <seq>
        <S/>
        <Name>FOO</Name>
        <S/>
        <contentSpec>EMPTY</contentSpec>
    </seq>
 </elementDecl>
</alt>


> Internal PEs are not really structural in XML;
> it is a mere validity constraint that requires DTD constructs to begin
> and end in the same PE, and
>
> <!ENTITY % element "<!ELEMENT">
> %element; FOO EMPTY>
>
> is a well-formed though not valid external subset.
>
> > Doesn't it make the most sense to subset from the full description,
rather
> > than both add to and subtract from a partial description?
>
> The question then remains, just what is
> useful structure and what is not?  I have done my best to answer that
> question.

Useful for the DOM and XPath, I agree, but since these already exist, and
define the middle subset, now is the time to define the full set.

I have no problem with what the Infoset is trying to accomplish as a subset
of XML 1.0 + Names (just as I have no problem with what Common XML etc are
trying to accomplish), but this activity needs to come from a complete base
down to X,Y or Z subset each of which are useful.

Jonathan Borden
The Open Healthcare Group
http://www.openhealth.org