xml-dev - RE: XSD: Proposed Goals, Rev. 3

[Tim Bray <tbray@textuality.com>]

At 03:04 PM 5/28/98 -0700, Andrew Layman wrote:
>(As I use the terms, "metadata" means descriptive information summarizing or
>supplementing a document, while "schema" means a collection of named items
>and their definitions, which names and definitions are necessary for
>understanding the document.  For example, a card catalog entry and a book
>review are both metadata (relative to the book) while a dictionary and
>grammar are schema.)

Supposing for the sake of argument that we accept these definitions
of the two terms, is the difference important?

It's far from clear to me that all information about information can be 
partitioned into "that which summarizes/supplements" and "that which is
necessary to understand".  Hmmm, if you re-write that second condition as
"that which can be used to support formal validation" then it starts
to sound like a really material distinction... boy, I get nervous when
we start bandying about the term "understand".  Arguably the common thread
that it's all information about information is more interesting.  But these 
are matters certainly open to debate.

I kind of think that the thing people have in mind in this group when
they say "schema" is "expressions of syntactic constraints which can
be verified mechanically" or some such.  But once again, it's certainly
useful to explore these issues so we have some shared grounding in what
people really want when they ask for schemas. -Tim

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