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   words (RE: extensibility in XSchema?)

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  • From: "Rick Jelliffe" <ricko@allette.com.au>
  • To: <xml-dev@ic.ac.uk>
  • Date: Mon, 22 Jun 1998 23:50:28 +1000

> From:  Simon St.Laurent
> Mark Anderson wrote:
(Not profoundness here) 

> >There seems to be a constant undercurrent of religion in xml-dev
> >about validation vs. parsing vs. semantics, whose portent I
> >don't apprehend. 
> I think for now I'm using the term 'verification', but this too 
> may change.  I have to admit that this is a religious war I 
> have no interest in participating in.   

When you use generic markup, i.e. when you are concentrating on
naming text ranges and entities according to their natures rather
than how a particular application will use them or the notation used, 
then "validation vs. parsing vs. semantics" become useful 
categories for discussion. Terms of art not of religion.

My theory is that industry people use "semantics" as jargon, with 
the following meaning--
	parsing:	reading a document, 
			categorizing the input in tokens,
			checking the tokens against lexical rules (WF);
	validation: checking the parsed document against some
			higher level grammar or schema (in particular
			the markup declarations of the DOCTYPE);
	semantics:	everything else.

So the terms exist not because of a world-view, but because they
describe categories springing out of XML as an actual technology.

Nevertheless, there is a great problem with "semantics".

So when someone says "XML cannot describe semantics" they are
actually restating that definition of XML rather than setting arbitrary
limititations--semantics can be described *IN* XML to the extent that
entities and relationships can be named and linked but not *BY* XML. 
IOW, XML lets you mark up your semantics according to your 
categories, but if they are not good categories that is your problem. 

And when someone says "XML can describe semantics" they are
actually either using "semantics" a different way to the usage above,
or they are saying XML *could* describe semantics if a much richer
set of types and operators were added, or they are saying that there
are some semantics which adopting a few extra conventions (e.g. 
architectural forms, RDF) make available. Or they do not see a 
difference between naming and describing--in which case XML's 
purpose is to describe semantics. 

This is why the particular word "semantics" is worthless. People
use it so equivocally that sentences containing the word are rendered
useless. I try to avoid the word now. I try to stick with SGML's
	text = data + markup
and use "data" and "information" wherever possible.

Rick Jelliffe

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