Re: A BACKUP HTML tag

Dirk Herr-Hoyman (hoymand@gate.net)
Tue, 25 Apr 95 08:17:43 EDT

At 7:30 AM 4/25/95, Paul Burchard wrote:
>hoymand@gate.net (Dirk Herr-Hoyman)
>> I would like to see <BACKUP> (or the moral equivalent) be
>> used to display a link that causes a Web browser to backup
>> to the last visited page.
>
>That's what <A REL="Back" ...> and/or <A REV="Next" ...> are for.
>
>Everything mentioned in this thread can already be handled by link
>relationships. HTML 3.0 will be much better about using them, so
>please let's not fall victim to <SPECIAL><PURPOSE><TAG><FEVER>. In
>terms of SGML, it's better to use structured attribute values than
>tags, when the need for continuing extensibility can be anticipated.
>

I am not at all in favor of adding new tags, if some existing ones will do.
Let's examine the REL/REV from the 3.0 <A> spec:

---------------------------- quote from 3.0 --------------------------------
REL
Used to describe the relationship of the linked object specified with
the HREF attribute. The set of relationship names is not part of
this specification, although "Path" and "Node" are reserved for
future use with hypertext paths or guided tours. The REL
attribute can be used to support search for links serving particular
relationships.
REV
This defines a reverse relationship. A link from document A to
document B with REV=relation expresses the same relationship as
a link from B to A with REL=relation. REV=made is sometimes
used to identify the document author, either the author's email
address with a mailto URI, or a link to the author's home page.
Tables of contents can use anchors with REV="ToC" to allow
software to insert page numbers when printing hypertext
documents. The plain text version of this specification was
generated in this way!
----------------------------- end of quote ----------------------------------

Note first of all, that the semantics for REL/REV are not defined here.
Who is going to do this registry? Yet Another IANA Registry?

I am wondering whether utilizing REL/REV for a "backup" use might not
conflict with some other use. Maybe, maybe not. Is it possible to have
multiple REL/REV on an <A>?

Someone has suggested that a URL be used here, which would really be an
internal use:

<A HREF="browser:backup">Back to where you came from</A>

which works in principle, but violates the nature of a URL. What happens
when some other agent (such as a Web worm) harvests this document, and
looks at this URL? I would rather see an attribute used, such as REV/REL
(or something else), than the HREF, which already has a defined role.

Looking at the 3.0 attributes for <A>, the only other one that looks to be
a candidate is CLASS.
---------------------------- quote from 3.0 --------------------------------
CLASS
This a space separated list of SGML NAME tokens and is used to
subclass tag names. By convention, the class names are
interpreted hierarchically, with the most general class on the left
and the most specific on the right, where classes are separated by
a period. The CLASS attribute is most commonly used to attach a
different style to some element, but it is recommended that where
practical class names should be picked on the basis of the
element's semantics, as this will permit other uses, such as
restricting search through documents by matching on element
class names. The conventions for choosing class names are outside
the scope of this specification.
----------------------------- end of quote ----------------------------------

The CLASS attribute is more flexible in that it can have a list of values.
It could be used to signal actions to the local browser, it since it is to
be used for styles (and presumably style sheets), it might be a uniform
place to define local brower commands, that get implemented in a style
sheet mechanism.

More than anything, this seems to be a matter of defining some conventions
for attribute values. Both REV/REL and CLASS conventions are NOT defined
in the 3.0 spec. Where are these going to be defined?

--
Dirk Herr-Hoyman <hoymand@gate.net> |          I tried to contain myself
CyberBeach Publishing               |                                but
   * Internet publishing services   |                          I got out
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