There is no one convention which will be applicable to all these uses
of <A HREF...>. However, given the constraints:
-- browser-independence,
-- obviousness
and
-- generality,
here is how I would go about designing each of those types of links.
DEFINITION
This is very straight-forward; the word or phrase to be defined is
enclosed in the <A>...</A> tags. It is absolutely excellent to find a
page like the UIUC OED page where practically every noun phrase is
linked, but because of the terrifyingly large amount of work that this
involves, I think tagging the first instance in each file is just as
acceptable as tagging every instance.
A case might be made for tagging the first instance after each <A
NAME=...></A> anchor definition.
CONTINUITY
I think a standard menu at the end works well for this, containing:
-- a link to the previous page
-- a link to the next page
-- a link to the top of the current semantic level
-- a link to the previous semantic level (section/chapter/book)
-- a link to the next semantic level
-- a link to the very start
For instance,
<H1>Navigation</H1>
Select an option from the list below:
<UL>
<LI> <A HREF="2-4.html">Go to the previous section</A>
<LI> <A HREF="2-6.html">Go to the next section</A>
<LI> <A HREF="2.html">Go to the start of this chapter</A>
<LI> <A HREF="1.html">Go to the start of the previous chapter</A>
<LI> <A HREF="3.html">Go to the start of the next chapter</A>
<LI> <A HREF="home.html">Go to the start of the book</A>
</UL>
DEPTH
I use this term to refer to information that may help to understand
the debate or development of discussion, but which (once accepted or
understood) can be accepted as true and omitted. This is a
mathematical lemma, for instance, or a reference that backs up a claim
you make. I generally would advocate a parenthetical comment with a
link to the document, eg.
Since the price of stoats has increased exponentially since
1955 (see <A HREF="...">Hahner and Hofner, JNEM, 1988</A>),
the cost of ...
or
With fifteen voters, compulsory voting and two parties, one
party must get at least seven votes (by <A ...>the Pigeon-Hole
Principle</A>).
TANGENTS
I draw a distinction between tangents and depth, based on the
relevance to the argument or theme development in the document the
link is from. For instance, if I'm describing what's on TV tonight,
links to cast lists for each of the shows would be depth, but links to
other shows the actors have been in would be tangential. There is
really no clear-cut method of identifying tangents, except to trust
the reader's intuition that tangential links are essentially
irrelevant to the current document's thread.
<A ...>David Thorpe</A>, who played the lead in <A
...>Wiggins</A>' <A ...>bowel</A>-shattering production of <A
...>Hamlet</A> in the <A ...>1960s</A>
Some would say that tangents ought to be eradicated, but the reason we
call the WWW clients ``browsers'' is that we can browse the world of
knowledge without keeping to the strict confines of the paths of
argument. If I had my way, careful authors would tag the tangents
specially to indicate frivolity or irrelevance.
NAVIGATION
When arranging information for quick navigation, menus seem to me to
be best. They can provide quick overviews of the destination of the
link, and are structured (vertically in most cases) so that the eye
can assimilate the whole in a comparatively short period of time. I
advocate the <DL> and the <UL>:
<H1>Our Campus</H1>
A spiel about the campus should go here.<P>
The following items of relevance to our campus are available
for browsing:
<DL>
<DT><A HREF="grounds/home.html">Grounds<DD>The groundskeepers
ensure a balance between buildings and nature is preserved.
<DT><A HREF="map/home.html">Map<DD>An aerial photograph, taken
in 1989 and enhanced by our graphics laboratory, provides the
basis for this guide to the campus.
...
</DL>
When you use ULs, I advocate placing the text of the link near the
start of the <LI> so that the text of the links make sense.
CERN's menus are good, offering shortcuts to items two levels away ...
<DT><A HREF="browser.html">Browser Menu<DD>Many browsers are
available: <A HREF="cern.html">the cern line mode browser</A>,
...
when the browser.html menu contains
<DT><A HREF="cern.html">Cern LineMode Browser<DD>This browser
is designed for terminals without full-screen capability ...
IN GENERAL
I always advocate placing meaningful text inside the <A>...</A> tags,
so that what the eye picks up as highlighted text provides an instant
clue to the destination. If all the eye sees when it scans a list is
a bunch of HEREs, then the owner of the eye is forced to read when
they shouldn't have to --- most links (currently) are navigation
links, and users should be able to find documents they are interested
in with a minimum of wasted time.
Remember, these are just my opinions and preferences. I've seen (but
god knows why) empty tags (<A HREF=...></A>) and other things that
defy explanation. Authors have the power to create almost any
document they wish, and the Jedi Jury is still out on precisely what
is the Dark Side of hypertext.
Nat