Definition of User Agent

To: UA List
From: Eric Hansen
Re: Definition of User Agent

This memo documents a suggestion that I made to Ian today regarding a change 
to the definition of "user agent".

There has arisen a mismatch between the language of the checkpoints and what 
we have meant by user agents. The checkpoints make requirements for the 
"user agent" but we really mean "the subject of the claim".

We also have the general mismatch between the title of the document "_User 
Agent_ Accessibility Guidelines" and the fact that we are really focusing on 
only a narrow set of "user agents". For example, the focus is on Web 
browsers without or without players and helper applications. Furthermore, we 
really don't expect a singular assistive technology to be evaluated by this 
document, even though it is technically, as "user agent".

I propose to change the definition of "user agent" so that that there are 
two meanings, one meaning user agent in the most general sense and another 
meaning "the subject of the claim".

I think that doing so can help bring everything into alignment. With this 
change, it is perfectly reasonable to use the phrase "user agent" in the 
checkpoints. Furthermore, the entire document becomes most assuredly about 
"user agents".

On a brief perusal of the document, I think that changes to make are very 
minor, a seemingly small price to pay for long-term consistency and clarity.

In a sense, all this change does is formalize what we have already done in 
the checkpoints -- allowed the term 'user agent' to refer to the subject of 
the claim.

The main changes as I see them are as follows.

Change 1: Change the definition of user agent.

Old (29 September 2000):

"User agent"
"A user agent is software that retrieves and renders Web content, including 
text, graphics, sounds, video, images, and other content types. A user agent 
may require additional user agents that handle some types of content. For 
instance, a browser may run a separate program or plug-in to render sound or 
video. User agents include graphical desktop browsers, multimedia players, 
text browsers, voice browsers, and assistive technologies such as screen 
readers, screen magnifiers, speech synthesizers, onscreen keyboards, and 
voice input software."

New:

"User agent"
"In this document, the term 'user agent' is used in two ways."
"1. Any software that retrieves and renders Web content for users. This may 
include Web browsers, media players, plug-ins, and other programs -- 
including assistive technologies -- that help in retrieving and rendering 
Web content."
"2. The subject of a conformance claim for this document, i.e., software for 
which a claim is made. This is the most common use of the term in this 
document and is the usage in the _checkpoints_. A _conforming user agent_ is 
a user agent for which the claim is _valid_. In order to emphasize this 
second meaning of user agent, this document instead sometimes uses the term 
'subject' or 'subject of the claim'.

========

Change 2: Fix the _explanation_ of our use of the term "user agent" in the 
checkpoints.

Old (29 September 2000):

"Each checkpoint definition includes:"

"(bullet) The checkpoint number."
"(bullet) The statement of the checkpoint. The statement of the checkpoint 
is one or more requirements that must be met by the subject of a conformance 
claim. For readability, the checkpoints refer to a single "user agent", but 
the subject of the conformance claim may consist of several software 
components."


New:

"Each checkpoint definition includes:"

"(bullet) The checkpoint number."
"(bullet) The statement of the checkpoint. The statement of the checkpoint 
is one or more requirements that must be met by the user agent (i.e., the 
subject of a conformance claim). As emphasized earlier, the user agent may 
consist of several software components."

====

Change 3: Possibly reduce reliance on the phrase "subject of the claim" and 
its variants.

One could possibly reduce reliance on the term 'subject of the claim' and 
its variants in Sections 3, but I don't know that it is essential. As noted 
in the definition, we sometimes use the terms ('subject', etc.) to make 
clear that we are referring to the second meaning of the term.

<END OF MEMO>



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Received on Tuesday, 10 October 2000 19:06:04 UTC