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Re: "Equivalency" in UAAG/WCAG, Checkpoint 2.3

From: Al Gilman <asgilman@iamdigex.net>
Date: Mon, 16 Oct 2000 07:46:36 -0400
Message-Id: <Version.32.20001015224239.04123150@pop.iamdigex.net>
To: "UA List (E-mail)" <w3c-wai-ua@w3.org>
At 07:25 PM 2000-10-13 -0400, Hansen, Eric wrote:
>Re: "Equivalency" in UAAG/WCAG, Checkpoint 2.3
>In your memo entitled "Minority opinons (equivalency has no 'target,' only
>'partners')" ([0]) you raised several important issues that deserve to be
>I hope that these responses are helpful. I will address the issues


An issue that I raised, and one you did not address, is seeking reasons
way) why checkpoint 2.3 _should_ be built using a more ordinary, symmetrical
model of equivalency, or the ordered relationship reflected in the language of
the current draft.

The alternative to the present language would be to take equivalency as "there
is some information that is represented in each, that is the same in both
[/all]."  This relationship is symmetrical.  This relationship is general. 
This relationship applies to an image and its alt text.  It applies to the
different-language subtitles for the same movie.  The point of building the
rule in this way is that it covers the widest range of cases with one
rule.  It
subsumes what people with disabilities need under a more general principle
benefits everyone.  

We fought long and hard to get the "author proposes, user disposes" protocol
established as the law of !important in CSS.

The purpose of 2.3 is to extend the guarantee of "author proposes, but user
disposes" to view control concerning any feasible choices in the view
extraction which can yield better usability for the user and still convey the
same information for the author. 

We should not be writing the checkpoint narrower than that (unless we then
multiple checkpoints for coverage). 

Because of the breadth of applicability, the principle is somewhat abstracted
from the particulars of many of the cases.  I agree it is a bit of a
stretch to
get people to think of the relationship between an image and a text phrase as
one of equivalence.  So the applicability is not totally obvious.  But people
can understand it when they think about it.  Many of the interesting cases are
polarized or ordered in some sense, but by using the equivalency relationship
(which is not so polarized or ordered) as the basis for applying the rule, we
get to all the cases that we need to cover, whether there is some additional
order or precedence among the equivalents or not.  The order is often present,
but it comes in addition to the equivalency we care about, not as an intrinsic

It may be argued that this is an internal matter to be settled whithin the
UAAG.  On the other hand, PF has a dependency on this point.  In dealing with
people defining new formats, it really helps PF to have the simple, broad
versions of the rule be what shows through clearly and consistently as the WAI
message from all corners.  That is why I have objected to the way that 2.3 is
presently stated.

Whenever the abstract, un-polarized relationship is true, the user should be
able to exercise control over which of the choices is exposed in the actual
view of the content.    If we put a more narrow test in the applicability
section of the rule, we run the risk that the rule as defined will not
apply to
all cases where it is needed.

Sorry not to give you a point by point reply, but I don't find your points
reflect what I was getting at very well.  So I have tried to assert afresh
I do see as the issue, 


>Question 1. Is the term "equivalent" the best term for expressing a
>uni-directional relationship between pieces of content?
>You have, in effect, posed the question as to whether the term "equivalent"
>is the best way to express such a uni-directional relationship. 
>In order to address this question, I want to start where I think (and hope)
>that we can all agree. Specifically, I don't think I hear any disagreement
>about whether the UAAG (29 September 2000) conception of equivalency is
>uni-directional (asymmetrical). The concept of equivalent is summarized in
>the following sentence from the definition of "Equivalent" in the glossary.
>"In the context of this document, an equivalency relationship between two
>pieces of content means that one piece -- the "equivalent" -- is able to
>serve essentially the same function for a person with a disability (at least
>insofar as is feasible, given the nature of the disability and the state of
>technology) as the other piece -- the "equivalency target" -- does for a
>person without any disability." (UAAG, 29 September 2000, definition of
>'Equivalents (for content)')
>Note that under this definition, just because content A is an equivalent for
>content B does _not_ necessarily mean than content B is an equivalent for
>content A. Thus, the relationship is uni-directional (asymmetrical) as
>opposed to bi-directional (symmetrical).
>Now let us get back to the question of whether the terms "equivalent",
>"equivalency target", and "equivalency relationship" can make sense for such
>a uni-directional relationship. 
>Let us consider the following excerpts the range of meanings found in the
>entry for "equivalent" in the on-line Merriam-Webster Dictionary [5]:
>"1 : equal in force, amount, or value; also : equal in area or volume but
>not admitting of superposition <a square equivalent to a triangle>"
>"2 a : like in signification or import b : having logical equivalence
><equivalent statements>"
>"3 : corresponding or virtually identical especially in effect or function"
>"4 obsolete : equal in might or authority"
>"5 : having the same chemical combining capacity <equivalent quantities of
>two elements>"
>"6 a : having the same solution set <equivalent equations> b : capable of
>being placed in one-to-one correspondence <equivalent sets> c : related by
>an equivalence relation"
>Some have expressed concerns that the UAAG concept of equivalent does not
>match meaning #1 ("equal in force, amount, or value"). Yet consider the
>other meanings. For example, meaning #6b ("capable of being placed in
>one-to-one correspondence") seems very compatible with our usage of the term
>as does meaning #2b ("having logical equivalence <equivalent statements>").
>Meaning #2a ("like in signification or import") and meaning #6c ("related by
>an equivalence relation") appear related, but not as directly.
>My conclusion from this review is that our usage of the term is well within
>the acceptable range of meanings for the term "equivalent". 
>It might be possible (or might have been possible) to find a different word,
>other than "equivalent" that would convey the uni-directional nature of
>"equivalent" and thereby avoid the sense of concern that we feel about the
>fact that our usage of equivalent does not match perfectly meaning #1 of
>equivalent ("equal in force, amount, or value").
>In conclusion, I have no problem with trying to find words that better
>express the uni-directionality of the relationship between an equivalency
>target and its equivalent. But at the same time, I am not persuaded that our
>current usage is seriously flawed.
>Question 2. Is the UAAG conception of equivalency fundamentally different
>from that expressed in WCAG?
>You have indicated that the UAAG concept of equivalency is contrary to that
>expressed in WCAG (1.0). You stated:
>"The "equivalent vs. equivalency target" definitions in this volume are not
>the same definition of "equivalent" as in math, English or the _WCAG_ and
>the math, English and _WCAG_ sense is appropriate in this context, and the
>usage currently in the draft is not." ([1], emphasis added)
>Although you did not seem to elaborate on this particular issue, insofar as
>I understand your concern, I disagree.
>Ian is correct in his suggestion that in crafting language for the UAAG
>definition of equivalent, I was trying to remain consistent with what is
>found in WCAG 1.0 [2].
>The WCAG 1.0 definition 'Equivalent' states:
>"In the context of this document, the equivalent must fulfill essentially
>the same function for the person with a disability (at least insofar as is
>feasible, given the nature of the disability and the state of technology),
>as the primary content does for the person without any disability." (WCAG
>1.0, definition of 'Equivalent')
>Please note that this definition, like that of the UAAG definition of
>equivalent, is uni-directional. The basic changes that we have in UAAG is
>that we give the relationship a name ("equivalency relationship") and that
>instead of using the term 'primary content' we use the term 'equivalency
>target'. I think that Ian would agree that the term 'primary content' has
>long been a 'fuzzy' (ambiguous) term that we haven't felt entirely
>comfortable with. I think that the working group is acquainted with my
>efforts to find a good definition for the term 'primary content'. And when I
>proposed the term 'equivalency target' [3], the working group accepted it
>[4]. As noted in the minutes [4], working group members seemed to appreciate
>its simplicity and that it neutralizes or eliminates some of the negative
>connotations that seemed associated with some definitions of 'primary
>In conclusion, I find the UAAG concept and definition of equivalency
>fundamentally in line with what is expressed in WCAG. Most to the point,
>both the UAAG and WCAG conceptions of equivalent are uni-directional
>(asymmetric) in their equivalency relationship.
>3. Is the current UAAG conception of equivalency simply the
>"primary/alternative" distinction but in different words?
>You indicated that "The current language (in the 29 Sept. Draft) is just
>primary/alternate content under new labels." I am reasonably certain that I
>disagree. I would be more certain if I knew that we were agreed about the
>meaning of the "primary/alternate" distinction. As I mentioned earlier in
>this memo, the term "primary" has long been known to have some ambiguity in
>it. And as you know, I struggled for quite a while trying to bring about
>some consensus regarding the meaning of "primary content" ([6], [7], [8],
>[9]) but ultimately failed [3].
>Notwithstanding some uncertainty about what is or should be meant by the
>term "primary content", I think I understand what you are referring to and
>will try to respond on that basis.
>I surmise that you think that the UAAG distinction "equivalency target
>versus equivalent" is another name for the distinction "content intended for
>people _without_ disabilities versus content intended for people _with_ any
>disabilities". A number of people found the latter distinction troubling in
>my discussion of "primary content"; in that context the distinction went
>under different names, sometimes "primary content/secondary content" and
>other times "primary content/alternative content". 
>As I indicated in a recent telecon, I have revised some of my thinking about
>the relevance and value of this distinction ([3], [4]). For the record, I
>will say that I think a better name for the distinction might be "core
>content" (intended for audience without any disabilities, plus any people
>with disabilities who can benefit from it) and supplementary content
>(intended for audience with disabilities who find the core content
>If this is what you meant when you indicated that "The current language (in
>the 29 Sept. Draft) is just primary/alternate content under new labels" then
>I disagree and will attempt to show how these distinctions are different. I
>will say that I expected this concern would arise and have been looking
>forward to the opportunity to clarify this point.
>The idea I would like to get across this: The concept of equivalency as I
>have been trying to articulate it is neutral_ as to whether any or both of
>the two pieces of content -- equivalent or equivalency target -- are
>intended for people with a certain disability status (e.g., with
>disabilities versus without disabilities). This means, for example, that
>there is nothing in the basic meaning of equivalent or equivalency target
>that denotes that one is intended for people with disabilities and one is
>for people without disabilities. 
>This may seem surprising since the UAAG definition of equivalent, which
>"In the context of this document, an equivalency relationship between two
>pieces of content means that one piece -- the "equivalent" -- is able to
>serve essentially the same function for a person with a disability (at least
>insofar as is feasible, given the nature of the disability and the state of
>technology) as the other piece -- the "equivalency target" -- does for a
>person without any disability." (UAAG, 29 September 2000, definition of
>'Equivalents (for content)')
>This definition makes clear reference to a person _with_ a disability at the
>'equivalent' end of the relationship and a person _without_ a disability at
>the 'equivalency target'. If so, then how can one then likewise affirm, as I
>do, that my concept of equivalency "is _neutral_ as to whether any or both
>of the two pieces of content -- equivalent or equivalency target -- are
>intended for people with a certain disability status (e.g., with
>disabilities versus without disabilities)"?
>The answer is essentially this: Just because content X serves essentially
>the same function for a person _with_ a disability and as content Y does for
>a person _without_ a disability DOES NOT MEAN that the author intends
>content X for persons _with_ disabilities and content Y for people _without_
>disabilities. The author's intended audience for a piece of content is _not_
>denoted by its status as an equivalent or as an equivalency target. That
>intention, insofar as it is important, must be designated by another means
>or, if necessary, guessed at. Let us consider an example of a Web-based
>instructional module that is teaching about _captions_ for multimedia
>presentations (movies, etc.) and that this instructional module is designed
>for all audiences. The captions are a kind of equivalent, specifically a
>text equivalent of the auditory track of the movie that is synchronized with
>the visual and auditory tracks. My assertion is that even though the caption
>text is a text equivalent for the auditory track of the movie, this does not
>mean that the author intends those captions, in the context of that
>instruction, specifically for people _with_ disabilities. Indeed, as we have
>said, in this case the author intends the caption text for people _without_
>disabilities (as well as people with disabilities who can benefit from
>Thus, I disagree that "The current language (in the 29 Sept. Draft) is just
>primary/alternate content under new labels." Personally I believe that the
>ability for an author to indicate that he or she intends some piece of
>content for persons with certain classes of disability. (I am confident that
>in some applications, this capability will prove essential.) The importance
>of this ability is increased by the fact that the distinction is between
>equivalent and equivalency target is _not_ a vehicle for conveying such
>information; in any given instance, one, or both, or none of the equivalent
>and the equivalency target might be intended for people with disabilities.
>On the other hand, the disability status of the intended audience was the
>_defining_ characteristic of the primary/alternative (or primary/secondary)
>I will reexamine the language of the UAAG document and see if there is a way
>that I can clarify this issue in the document. 
>Thanks for giving me the opportunity to discuss this point.
>Question 4. Should checkpoint 2.3 be altered to take in a greater variety of
>Judging from comments on the list, there seems to be quite a bit of interest
>in expanding the scope of checkpoint 2.3.
>I think that this is a very good point to bring up. Your suggestions have
>helped me think through my concerns about things that don't fit into the
>regular mold of equivalency relationships.
>Here is my suggestion for checkpoint 2.3:
>"2.3 Where multiple elements of content within a document are related by
>_equivalency and similar relationships_, provide easy access to each element
>among the related elements. This shall be done through at least one of the
>following mechanisms: (1) allowing configuration to render one element
>instead of other related elements; (2) allowing configuration to render more
>than one of the related elements; (3) allowing the user to select a
>displayed element and then inspect any of the other elements; (4) providing
>a direct link to other related elements, just before or after a displayed
>element in document order.
>[Priority 1]"
>"Note: For example, if an image in an HTML document has text equivalents,
>provide access to them by (1) allowing configuration to replace one element
>from among the image and its rendered equivalents;  (2) allowing
>configuration to render an image plus one or more of its rendered
>equivalents; (3) allowing the user to select a displayed image or equivalent
>and then inspect any of the other elements; (4) providing a direct link to
>other related elements (image or equivalent), just before or after a
>displayed element in document order."
>"Techniques for checkpoint 2.3"
>Also, add the following to the definition of Equivalent or in a Note:
>"_Equivalency and similar relationships_ include at least the following:
>equivalency relationships; linearizations and summaries of tables;
>expansions (of acronyms); abbreviations (of phrases); language translations;
>titles, etc."  
>Comment 1:
>I used a "defined" term "element" rather than an undefined term "fragment";
>provide the example; defined the "equivalency and similar relationships". 
>Comment 2:
>I presume that we don't need to mention that they only need to work with
>what they can recognize.
>Comment 3:
>I suspect the definition of "Equivalency and similar relationships" needs
>further work.
>Below for comparison are (1) the old (29 September 2000) version of
>checkpoint 2.3 and (2) Al Gilman's suggestion.
>Old (29 September 2000):
>2.3 Provide easy access to each equivalent and each equivalency target
>through at least one of the following mechanisms: (1) allowing configuration
>to render the equivalent instead of the equivalency target; (2) allowing
>configuration to render the equivalent in addition to the equivalency
>target; (3) allowing the user to select the equivalency target and then
>inspect its equivalents; (4) providing a direct link to the equivalent in
>content, just before or after the equivalency target in document order.
>[Priority 1] 
>Note: For example, if an image in an HTML document has text equivalents,
>provide access to them (1) by replacing the image with the rendered
>equivalents, (2) by rendering the equivalents near the image, (3) by
>allowing select the image and then inspect its equivalents, or (4) by
>allowing the user to follow readily available links to the equivalents. 
>Techniques for checkpoint 2.3
>Al's suggestion:
>2.3 Where there are multiple fragments of content within a document which
>are equivalent in the senses that they convey the same information, closely
>or roughly; provide easy access to any equivalent among the range of
>This shall be done through at least one of the following mechanisms: (1)
>allowing configuration to render one equivalent instead of another; (2)
>allowing configuration to render more than one equivalent; (3) allowing the
>user to a displayed equivalent and then inspect any equivalents of the
>selected item; (4) providing a direct link to another (each other)
>equivalent in content, just before or after a displayed equivalent in
>document order.
>[Priority 1]
>("Primary content -- OK as a "Fuzzy" Concept?")
>("Primary Content", etc. - Response to Ian Jacobs)
>("Primary Content", etc. - Corrected!)
>(""Primary Content", etc.")
>Eric G. Hansen, Ph.D.
>Development Scientist
>Educational Testing Service
>ETS 12-R
>Princeton, NJ 08541
>609-734-5615 (Voice)
>E-mail: ehansen@ets.org
>(W) 609-734-5615 (Voice)
>FAX 609-734-1090
Received on Monday, 16 October 2000 07:22:27 UTC

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