Entities in XSchema
papresco at technologist.com
Thu Jun 11 06:01:52 BST 1998
John Cowan wrote:
> I used the term "IDspace" in a previous posting. However, your
> FIGID value can be just an ID value if it is prefixed with "FIG-"; where
> you would assign a FIG-unique FIGID value, just assign a prefixed
> and document-unique ID value.
Unfortunately, this means that the *name* of objects must also have the
prefix. To get back the unprefixed name you must other do string hacks or
have another attribute with the name.
More subtly, but also more importantly, we are making the system
redundant. You are well aware, I am sure, that redundancy can be useful,
but you also no that it can be fatal. Using my simple example of FIG, I
might someday rename the FIG element to GRAPHIC. Now I must change all of
those ID values as well.
Anyhow, the most important reason to want more sophisticated ID-uniqueness
checking is because it is painful to have IDs that are the moral
equivalent of FIG-NAMED-SPAM-IN-CHAPTER-NAMED-MONTY. Coordinating and
communicating the convention is nigh impossible.
> > IDREF should also be more powerful. It should allow full XPointers (though
> > an XSchema processor might only check local ones).
> This is rebuilding XLink. ID/IDREF have the advantage of being
> very small and very cheap.
I'm not suggesting we rebuild XLink. I'm suggesting that we build on it.
If we are going to check hypertext links in XML, we should check
XPointers, not ID/IDREF. ID/IDREF is mostly there for backwards
compatibility. The XLink group has decided not to explicitly support
ID/IDREF, so we should probably follow their lead. Of course XLink is
still under development, so that part of the XSchema spec. should probably
just be left out for now.
Paul Prescod - http://itrc.uwaterloo.ca/~papresco
Three things are most perilous: Connectors that corrode
Unproven algorithms, and self-modifying code
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