Link style sheets [was REL and REV]

Terry Allen (
Wed, 10 May 95 20:36:57 EDT


Right. Now why use PIs at all?

| It isn't explicitly stated in the HTML draft, but I'd say that
| browsers are already required to support PIs by virtue of
| the first sentence of section 2:
| HTML is an application of ISO Standard 8879:1986 - Standard
| Generalized Markup Language (SGML).
| Most current browsers do in fact support (i.e., ignore) PIs
| by treating them as "unrecognized tags".

Netscape really ought to try implementing its extensions, such
as <blink>, as PIs. It would be most appropriate wrt SGML and
HTML, it would cause no interoperability problems, and they
could recognize only their own PIs if they chose.

However, for the case in hand, you have the obvious solution

and then you put all that info outside the current document,
where you can reuse it.

What is really being proposed here is a style sheet for linking
semantics. This is something we can make great use of. For
you Hytime fans, this is where you could hook up your Hytime
engine to the linking API (which would apply to HTML, PDL, RTF,
SGML, etc.).

Panorama currently refers to style sheets through PIs, but it's
an engine for arbitrary DTDs. For the case of HTML we could well
establish a specific, element/attribute hook.

I notice that in the latest 3.0 DTD I have, there is an entity
<!ENTITY % Misc.Relations "stylesheet|node|path">
but that the entity is never used.

| > I suppose you could do
| > <HEAD>
| > <LINKSET HREF=".....">
| > <LINKSET HREF="......">
| > <LINK REL=.... HREF=....>
| > <LINK LINKSET=.... REL=..... HREF=.....>
| > </HEAD>
| >
| > but I think this is more complex than necessary.
| >
| > The idea of sets of link semantics that can be associated
| > with a URI _does_ seem sound to me. I'd rather do it without ProcInsts if
| > we can.
| I would prefer PIs over elements for this purpose: the support
| declaration is after all an application-specific instruction,
| which is exactly what PIs are for, and the declaration syntax
| could be more easily extended without changing the DTD. But
| the exact markup isn't crucial, IMO.
| (I've noticed that many SGML gurus seem to have an instinctive
| mistrust of processing instructions... I wonder why that is?)
| --Joe English

Terry Allen  (   O'Reilly & Associates, Inc.
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