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

Clark Evans clark.evans at manhattanproject.com
Fri Feb 19 05:13:11 GMT 1999

Marcus Carr wrote:

> I think you might be applying a meaning to that
> phrase that it doesn't deserve - it doesn't call XML
> a document standard, it uses the term "XML document",
> with document defined in the XML recommendation as:
> "A data object is an XML document if it is well-formed, 
> as defined in this specification. A well-formed XML document 
> may in addition be valid if it meets certain further constraints."
> This allows you to use the phrases "XML data object" and 
> an "XML document" interchangeably.
> This isn't incongruous with stream markup - you just need to 
> consider the stream as an XML document. Seriously though, you 
> probably wouldn't have the same concerns about "XML data object" ...

My concerns would be even greater.  This conjures up in my
mind a Java or C++ object where the complete stream 
has to be loaded in memory (or some other random-access
medium) before it can be used.  Yes, I know you can have 
a multi-threaded implementation so that you can start using 
the data object before it finishes reading, etc.  However, 
given the object model it is *reasonable* for the niave 
programmer to ask for something at the _end_ of the stream.  
This will cause the call to block untill the stream ends.

If "data stream" processing was treated with *equal*
importance by the W3C committees, then they would see,
in many cases, that this complementary approach is at 
least as good as, or in some cases far superior to 
an "data object" approach.

Constantly viewing XML as a standard for the description 
of "data objects" and not "data streams" is a subtle, and 
important bias.  It is taking object-orientation too far 
and discarding parallel stream processing, and it's related
technologies like SAX and SAXON.

:) Clark

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