XML Information Set Requirements, W3C Note 18-February-1999

Simon St.Laurent simonstl at simonstl.com
Sat Feb 20 13:47:07 GMT 1999

Jeffrey E. Sussna wrote:
>I would like to encourage the XML community to 
>1) pay attention to the lessons of 30 years of development in the arena 
>programming and type languages, and 
>2) not get bogged down by the historical baggage of the M in XML.

And then Paul Prescod wrote:
>The role of the information set requirements committee is to make explicit
>the implicit data model described in vague terms in the XML specification.
>Their responsibility is not to point XML in a bold new direction. 

And then James Tauber wrote:
>XML came about to solve issues in structured document interchange on the
>web. Perhaps largely because the language syntax was developed more quickly
>than linking or stylesheets, people started using XML for a broader range of
>If XML meets the needs of people working on those broader range of problems,
>then they can go ahead and use XML, but I would be extremely disappointed
>(as I'm sure many people who contributed to the original development of XML
>would be) if XML shifted away from being a solution for structured document
>If XML "moves away from being markup oriented" as you suggest is already
>happening, then XML will no longer be a solution to the very problems it was
>designed to solve.
>Long live XML for publishing!

It seems that some of XML's original denizens aren't too happy about
proposals for making XML useful in a broader set of fields than document
publishing and interchange.  Paul pours cold water on having the Infoset
group ponder anything new, and James says he'll be disappointed because XML
is no longer focused on its original problem set.

Why so glum?  This is hardly a bomb-throwing anarchist's proposal.  XML has
proven to have a lot of appeal to people outside of the original
document-oriented audience (which includes myself).  The delays in tools
for managing, creating, linking, and presenting XML documents have left XML
without very much to do for documents - presenting unlinked documents in
beta viewers isn't especially exciting, and so far XML hasn't made much of
a dent on its original claim to be 'SGML for the Web'.

Instead, XML has moved into a lot of new fields, driven by the needs of
programmers who finally have a very standardized syntax for communicating
all kinds of information (okay, fine, not binary data) in a way that's easy
to debug (dump to file, and you might actually find something!) and (wow!)
works across different environments and platforms.  Throw in ease of
transformation (with XSL or whatever) and it's an amazing package.

If you take the stance that XML is about documents and only about
documents, it may seem that these proposals for XML are in competition with
document-oriented applications.  They may even drain resources needed for
the further development of document-oriented applications, whether or not
they are 'officially' in competion.  (Much the way I see XSL in regard to
CSS, actually.)  The document-based 'hammer' is getting used on screws,
from this point of view.

On the other hand, these folks are interested in XML, ready to make it
work, and in some cases, creating real implementations.  Astronomical
Instrument Markup Language (AIML) uses XML in support of command and
control of remote astronomical devices, building user interfaces and
sending commands based on information in XML documents.  Coins and MDSAX
can pretty much construct a Java program for you using XML (and not just a
single vocabulary) to knit together a group of objects.  There's a lot of
impressive work out there that isn't  in the realm of traditional 'documents'.

As far as streaming is concerned, it seems like the hardest thing in its
way is the prolog and the requirement of a root element.  Establish the
prolog information at the start of the stream, figure out a way to end a
stream, and go.  That Extensible Protocol (XP) thing I mentioned earlier
might be an easier way to deal with these issues than changing XML itself -
it's a draft at the IETF that seems to address many of the streaming
concerns, without having to explode documents.  See 
 for details.

Simon St.Laurent
XML: A Primer / Building XML Applications (April)
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