RE: [xml-dev] Symbol Grounding and Running Code: Is XML Really Extensible?

["Dare Obasanjo" <dareo@microsoft.com>]

> -----Original Message-----
> From: Bullard, Claude L (Len) [mailto:clbullar@ingr.com] 
> Sent: Wednesday, August 13, 2003 7:17 AM
> To: 'Alaric B Snell'; xml-dev@lists.xml.org
> Subject: RE: [xml-dev] Symbol Grounding and Running Code: Is 
> XML Really Extensible?
> 
> Thank you, Alaric.
> 
> Finally, someone thinks architecturally, that is, 
> systematically, which is the point of the symbol grounding 
> article:  one cannot ground symbols without a systematic 
> means for compositing the primitives of the symbol set into 
> meaningful statements where meaningful, in our case, is 
> running code.  Note also that the article clearly delineates 
> human behaviors, and even if we 'intend' machine behaviors, 
> it is the coupling of symbols to behaviors that form the system.  

Alaric doesn't posit a general solution which is what my original post
is about. Anyone can come up with an namespace-based extension
architecture for a specific XML vocabulary where extensions perform a
single specific task. The RELAX NG folks have shown us how to do it
already with pluggable datatypes based on namespace URIs. Something
similar could be built into XSLT and W3C XML Schema engines if the user
demand for such features was that significant. 

However such specific implementations aren't really relevant to the
original discussion which was about how to signify "meaning" in
something like a syndication feed which could be extended in any
possible direction as opposed to one narrowly focused direction. 

Of course the original discussion is pipe dream Semantic Web goop while
this discussion is actually of practical interest. 


> Dare:  Internet Explorer.  See the means for annotating the 
> presence of VML in an HTML document. 
> Big surprise.  It uses a namespace declaration. 

I don't consider this embedding semantics. This is simply a rendering
engine delegating rendering of embedded markup to plugins based on
whether it has or knows of a renderer for the embedded markup. The fact
that VML in IE requires you to put the VML namespace decl on the root
element of the HTML page is probably more for practical reasons
(performance, initialization, etc) than anything else. 

 
> So clearly namespaces rightly or wrongly, morally or 
> indefensibly, big endian or little endian, without regard to 
> the philosophical or legal or sanctioned efforts of the 
> standards committees ARE BEING USED TO ATTACH SEMANTICS TO XML TAGS.

Namespaces attach some form of identity. Without this identity
processors of XML vocabularies would not be able to process XML. How
does a W3C XML Schema validator or XSLT transform engine determine
whether it has a schema document or stylesheet? By the local name and
namespace name of the root element of the document it has been fed. 

As Tim Bray said, namespaces aren't relevant to the symbol grounding
discussion and just add a layer of indirection. 
 
> One needs a way to describe an abstract object 
> model of the browser that is mappable to the XML namespaces 
> and by which, one can easily declare meaningful combinations.
> 
> RSS won't be extensible in and of itself without something 
> similar.  We really must differentiate XML language design 
> from XML system design.

A web browser does one thing and one thing only; render markup. It is
trivial to design a system that says render markup from namespace A with
engine A and markup from namespace B with engine B modulo some
constraints with regards to location of embedded markup. 

RSS feed aggregators do not perform a single task with the markup in an
RSS feed and can perform any one of dozens of things with embedded
markup. 

-- 
PITHY WORDS OF WISDOM 
Eat right, Exercise, Die anyway.


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