Re: Hyperlink behavior

At 10:45 AM 12/20/96 -0500, David G. Durand wrote:

>   We need to add a level of abstraction to HyTime and ensure that the
>specification of behavior of links is in the style sheet, and not in the
>document markup. 

I heartily agree with everything David said, except for the above, at which
I bristle at only because HyTime does *NOT* have any built-in facility for
defining hyperlink behavior.  The closest it gets are the optional
traversal rules which only define constraints on *movement* between anchors
or between members of multi-object anchors (what we used to call "aggregate
anchors" but which are not called "list anchors").  Some of these movement
options have obvious natural behaviors (a "return only" anchor could
naturally be presented in a restricted modal window) but these behaviors,
or in fact any behavior, are explicitly *not* implied or required by these
rules.  They serve only to augment the data modeling facility of
hyperlinks.  For example, if your purpose in creating hyperlinks is to
describe the relationships among the steps in a process, part of the data
model of the process may be that movement from one step to the previous
step is not allowed (the application we use when discussing traversal
design is a Zork- or Dungeon-type game where doors between rooms are
represented by hyperlinks.  Traversal rules can be used to indicate things
like doors that lock behind you (return not permitted) or traps (no further

By "add a level of abstraction to HyTime" I assume David means the further
specialization of HyTime forms to either simplify them or add XML-specific
features, both of which are the way HyTime is supposed to be used.  If, on
the other hand, there is a deficiency in the HyTime design such that it is
insufficiently abstract, I'd like to know because there's still time to
change the TC if it's not a big change.  However, I sincerely doubt that
HyTime could get much more abstract.

The HyBrowse browser (free from www.techno.com) demonstrates very nicely
the power of being able to associate behavioral and presentation styles
with hyperlinks based on link types and anchor roles.  I urge everyone
involved in this discussion to rush out and download it (Windows only for
now, I'm afraid--they're not charging enough for it to support development
of other platform versions).  Peter Newcomb tells me that they are in the
process of integrating the current SP version into it which will, in part,
make it Internet enabled.
HyBrowse does not yet reflect the HyTime TC.


W. Eliot Kimber (eliot@isogen.com) 
Senior SGML Consulting Engineer, Highland Consulting
2200 North Lamar Street, Suite 230, Dallas, Texas 75202
+1-214-953-0004 +1-214-953-3152 fax
http://www.isogen.com (work) http://www.drmacro.com (home)
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