Re:Re Hytime for HTML 3.0

Christophe ESPERT (
Thu, 23 Mar 95 03:38:23 EST

In message <199503221810.KAA26916@rock> 22 Mar 95 13:14:01, wrote:

> You remark re entity management:
> >HTML is doing it with the URL mechanism and this is not exactly the
> mechanism proposed by SGML.
> But URLs are not forbidden by ISO 8879, which might be inferred from
> your statement. On to the excerpts:

Yes ISO 8879 allows you to do what you want and that's nice. I am sorry
if my statement inferred this. I am just trying to point out that there
is a standardized feature in SGML (entities) and that they could be used.
And I also know that this messing up the location mechanism in W3.

> <!ENTITY target-doc SYSTEM "" CDATA SGML>
> <!-- The target document is declared as a data entity conforming to
> the SGML notation declared at the bottom of this DTD -->
> <!-- Other entity declarations will go here -->
> ]>
> <HTML>......
> <A linkends="nmloc-target"><!-- one link end has been omitted and
> it corresponds to the element A itself -->
> Here is the anchor that will lead me to the target document.
> <NMLOC id=nmloc-target><NMLIST docorsub=target-doc>target-id</NMLOC>
> <!-- You can see that the target-id is in the content of the NMLIST
> element. -->
> ......</HTML>
> You forgot to close the A (and NMLOC is allowed only within A in your
> DTD, which is not too flexible).

Thank you for this. I put arbitrarily the NMLOC element as an inclusion
exception on A. I know this is not too flexible. But we can put it
anywhere you like... It won't change anything.

> Also, as the information that is to be dispatched via HTTP
> when a user clicks on a Hy-A link is in fact a URL (here, the value
> of the docorsub att on NMLIST concatenated with the element content
> of NMLIST according to rules not expressed in your Hytime additions
> to the 3.0 DTD), um, what's the advantage of expressing things this
> way, except to adopt some of the Hytime formalism?

This is a very interesting question. Right now there are only one to
one links on the Web. In an NMLIST element you may put several IDs
from the target document. So you can link to several locations.
Moreover you can have several NMLIST elements in the NMLOC so that you
can link to multiple locations belonging to several documents (because
of the docorsub attribute on NMLIST). Right now it might not be
interesting (in HTML 3), but I am sure this is something people will
want in the future.
I know this is the opening of a can of worms. But it is interesting
to discuss.
Best regards,
PS: I forgot to say to Chris Lilley that I have followed the discussions
regarding the MIME text/sgml content type. There are only extremely
competent SGML people doing it and they came up with a very good solution
so far.

Christophe Espert - E-mail:
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ISO 8879:1986 - SGML | ISO/IEC 10744:1992 - HyTime | ISO/DIS 10179 DSSSL