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Re: Linking in DocBook (specifically for EBNF, but more generally as well)
- To: docbook at lists dot oasis-open dot org
- Subject: Re: DOCBOOK: Linking in DocBook (specifically for EBNF, but more generally as well)
- From: "Eve L. Maler" <Eve dot Maler at east dot sun dot com>
- Date: Fri, 07 Apr 2000 17:23:08 -0400
- Reply-To: docbook at lists dot oasis-open dot org
At 01:36 PM 4/7/00 -0700, Terry Allen wrote:
>| <nonterminal xlink:href="#foo">
>
>1. Is this correct Xlink syntax for a pointer to a single target?
>(I knew shortly after I read the Xlink spec but have forgotten.)
It's correct XPointer syntax for identifying an element with this value for
its ID-type attribute.
>2. Is Xlink stable in this regard?
The ID functionality is stable because XPath is already a W3C
Recommendation. The #foo shortcut is specific to XPointer. I can't
promise that it's stable, but XPointer has exited Last Call and will soon
(I hope) enter its Candidate Recommendation period (sort of a beta period).
>3. Has Xlink been implemented?
In this case, it's XPointer. The CR period is supposed to determine
whether the entire spec is implementable; we're anticipating success at
this, since 95% of XPointer is XPath. I don't know any (e.g.) browsers
that support XPointer yet in fragment identifiers on URIs, but that's not
surprising. I know of some internal use of the #foo shortcut, where a
trivial transform is done to turn it into a classic IDREF.
>4. Will "#foo" work like ID/IDREF in current tools? (I would
>think it wouldn't.)
No.
>I see the need, but I'd like not to get to the party too early.
DocBook has been waiting for linking standards to stabilize for at least
five years; perhaps we won't have to wait much longer.
We don't have to decide to go the one-attribute route right away, but the
two-element solution that you suggest seems to be merely an artifact of the
lack of expressive power in DTDs, and it would be a shame if that were the
long-term solution. (By the way...the RELAX schema language allows you to
define alternative versions of element constraints based on attribute
values, which would be a neat way out of this design dilemma. :-) I'd
rather have two attributes and an extra-DTD constraint than two elements.
Eve
Eve Maler +1 781 442 3190
Sun Microsystems XML Technology Center elm @ east.sun.com