UA techniques for abbr and acronym

[Beginning with the definitions that better distinguish between these,
as developed by the Digital Talking Book 3.0 team, and replacing
the confusing ones in HTML documentation:]

Explanation: abbr designates an abbreviation, a shortened form of a word.

Explanation: acronym marks a word formed from key letters (usually
initials) of a group of words. For example: UNESCO, NATO, XML.

An abbr or acronym tag encloses "content" that represents its
"expansion". The enclosed content should not include surrounding
parentheses, as often appears at the first occurrence.

A user agent should be prepared for the user to ask what the
abbr or acronym tag content means, and return to the user the
expansion [Priority 2].

A user preference should allow expand/ignore expansion of the content
for all as encountered, or just the current abbr or acronym. [priority 2]

-------------- References -----------
1. Authoring Tools PR

Checkpoint 3.1: Prompt the author to provide alternative information (e.g.,
... expanded versions of acronyms, ...)

2. Web Content Accessibility Guidelines
Guideline 4

... Content developers should also provide expansions of abbreviations and 
acronyms.

4.2 Specify the expansion of each abbreviation or acronym in a document 
where it first occurs. [Priority 3] For example, in HTML, use the "title" 
attribute of the ABBR and ACRONYM elements. Providing the expansion in the 
main body of the document also helps document usability.
-------------
Web Content Accessibility Technique

4.3.2 Abbreviations and Acronyms

Checkpoints in this section: 4.2.
Mark up abbreviations and acronyms with ABBR and ACRONYM and use "title" to 
indicate the expansion ...[example]
---------------

Assume good authoring practice, as indicated above:

At least on first occurrence of an abbr or acronym tag for a particular
content , the title attribute value in that tag includes the expansion, 
title="expansion". That expansion is typically included in the text at
first use, as a courtesy to the traditional user, who was expected to
read linearly, and remember the expansion.

However, the assumption of linear reading of an entire document
is often invalid for web reading. The first occurrence may well be
in a different URI.

Technique 4.3.2 above indicates that every abbr or acronym tag should have
title="expansion". In this case, any such tag has its expansion locally.

A user first encountering the content of an abbr or acronym, without
its expansion there, the abbr or acronym content and its expansion
could be located in an index, glossary, list of abbreviations or acronyms.

Two authoring approaches might be used:

1. Title attribute for expansion

1a. Each occurrence of an abbr or acronym tag should have the attribute 
title="expansion" in its start-tag. This is the most straightforward,
as it allows the user agent to render that title value on user request.

[Assume an authoring tool that requests the expansion corresponding to the
content of any new abbr or acronym, and then assigns it to the title
attribute of that tag. Thereafter, whenever such identical content
is included in such tag, the authoring tool can then add the known 
title="expansion" to the tag.]

A user wanting an expansion of an abbr or acronym then has it available
at the point of regard, and the user agent should respond to the user
query for expansion from the title="expansion".

1b. Ideally a user agent, on encountering an abbr or acronym tag
without the title="expansion" should be able to find that expansion
from the first use of that tag content.

A user agent might keep a list of all content and expansions of abbr
or acronym. Then occurrences of the tag with recognized content could
in the absence of title="expansion" use that prior expansion. This
fails when the title="expansion" location is from an unvisited URI.
In that case, the user agent can only indicate the expansion has not
yet been encountered.

An authoring tool might maintain the convention of keeping a definition
list of each abbr or acronym content and its expansion, so it is prepared
to fill in the title="expansion" of those tags.

2. Hyperlinking from abbr or acronym content to definition

2a. Assume the first occurrence has a target anchor <a name="...">
surrounding the definition that often precedes the actual abbr or
acronym, and each such actual tag has an anchor <a href="#...">
pointing to that initial definition. An advantage of this approach
is that only one definition is required. A disadvantage is that this 
definition may be in a different URI, and the disruption in reading
flow to go elsewhere, then back may be difficult.

2b. If the expansion text for the abbr or acronym is in the glossary,
or list of abbreviations or acronyms, then that definition could be
enclosed in the target anchor. User request for expansion would get
that value from the remote location. The same disruption of reading
flow occurs, with the need to go back.

Regards/Harvey Bingham