Validating IDREFS...

Michael Kay M.H.Kay at
Tue Sep 1 19:22:27 BST 1998

MK>> ... the real difficulty with [IDREFs] is ... the fact
that they are
MK>> incompatible with XPointer.
Chris Maden>That's not true.

I can use either an IDREF or an XPointer (within an XLink,
or otherwise) to define a reference by ID to another element
in the same XML document, but there are differences:

* The syntax is different ["idval" versus "ID(idval)" or
* I can have several IDREF attributes in an element, but
only one XLink attribute
* A dangling IDREF is an error; a dangling XPointer is not

That is what I mean by saying the two facilities are
incompatible. Or to put it another way, once I have made a
design choice to use IDREF or to use XPointer for the links
in my documents, I am stuck with my choice.

This is one of several situations in the XML family of
standards where there is more than one way of doing the same
thing, and no obvious way to choose between them. As the
frequency of questions about the element-vs-attribute choice
shows, this confuses users no end; it also complicates
software tools.


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