Streaming XML (Was RE: XML Information Set Requirements, W3C Note 18-February-1999)

Borden, Jonathan jborden at
Wed Feb 24 03:06:34 GMT 1999

Steven R. Newcomb wrote:

> I certainly can't speak for James, but I would
> like to clear something up:
> ISO/IEC 10744:1997 ("HyTime") and, earlier,
> ISO/IEC 10179:1996 ("DSSSL") defined and coined
> the term "grove".  A grove is the set of objects
> resulting from parsing an information resource in
> some specific notation.  EVERY GROVE ALWAYS MUST
> CONFORM TO A FORMAL MODEL called a "property set".
> The "SGML property set" is one such property set,
> and it's the property set that governs the
> structure and nature of the objects to which
> Jade's groveoa interface provides access.  Think
> of a property set as a schema for the objects that
> result from parsing (and/or from semantic
> processing, but that's another story for another
> day).

	Thanks for clearing this up succincly. I suppose I have the inappropriate
tendency to read code more often than specs, so the source of my
suppositions has been from projects like Jade rather than the true source.

> The DOM is not a grove; it is an API.  Until the
> XML information set is stable, the DOM is an API
> to something that's not rigorously defined.  The
> DOM can be implemented as an interface to XML
> groves, but not before there are XML groves.  And
> there can't be XML groves until there's a property
> set for XML.  (Well, no, that's not quite right,
> because we routinely make SGML groves from XML
> documents.  But that's just a temporary kludge
> that only works because of XML's SGML parentage.
> Moreover, the SGML Property Set provides for more
> complexity than XML groves will ever need to have,
> and simplicity is one of XML's most important
> virtues.)

	Interesting. Is the DOM just an API, or a set of interfaces which define a
heirarchy of objects? That is, an IDL interface definition is a type of
formal definition. For example, using Microsoft's COM, IDL compiles into a
'typelibrary' which is a binary representation of something analogous on
some level to a property set. A scripting language, to continue the example,
can employ any object with a typelibrary and associated interface set.

	Would it be possible to generate IDL programmatically from a property set
definition? If so, then aren't the two alternate representations of the same

> There is every reason to believe that the XML
> Information Set, once Recommended, will be
> expressible as a property set.  Once this is done,
> XML objects will be processable, addressable, and
> re-usable via the same software that supports the
> processing, addressing, and re-use of components
> of resources expressed in other notations, with
> each such notation described by its own property
> set.  In that scenario, all information components
> conform to the same object model, the ISO "grove"
> object model, so we are able to address (link,
> re-use) any kind of thing.

	This is the same language used to describe the virtues of COM. Not to
denegrate the virtues of property sets, but why are property sets
specifications, and IDL definitions an API?

Jonathan Borden

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