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Comments on XML Accessibility Guidelines (29 August 2001 draft)

From: Ian B. Jacobs <ij@w3.org>
Date: Tue, 25 Sep 2001 19:20:56 -0400
Message-ID: <3BB11158.1AB1F51C@w3.org>
To: wai-tech-comments@w3.org
CC: ij@w3.org
Hello,

Here are some preliminary comments (preceded by IJ:) about
the XML Accessibility Guidelines:
  http://www.w3.org/TR/2001/WD-xmlgl-20010829

I'm glad to see this important document advancing. I think it
should be moved to the Recommendation track for at least two
reasons:

 - It should undergo the same scrutiny and review as the
   other WAI Guidelines. If it does not, it is likely that
   people will refer to it as though it had the same standing
   as the other WAI Guidelines, even if the authors warn against
   this.

 - It deserves the same status as the other documents and I think
   it should be a core document on which the others depend. WCAG
   should ask authors to use formats that conform to XMLAG. 
   UAAG should require that developers implement formats that
   conform to XMLAG.

Sorry for the length of this email.
Thank you for your hard work,

 - Ian

P.S. In a separate email, I suggested that future versions of this
document carry version number "1.0".

> XML Grammars, and The Scope Of XMLGL
> 
> The  XML  grammars (called schemata - but see the caveat about our use
> of  the  term  "schema"  in  the definition section) can be classified
> along two different axes:
> 
> Data-oriented:
>        Tagsets  for:  User Interface (UI)--oriented structural textual
>        rendering,   such   as   Docbook,   HTML,  MenuML,  OEB,  etc.;
>        specialized  rendering  -  for  example MathML, Scalable Vector
>        Graphics  (SVG),  MusicML,  Synchronized Multimedia Integration
>        Language  (SMIL);  or  any  generic  data  storage  format.  An
>        informal  definition  is  'anything  for which the question "is
>        there  a textual equivalent of all rich media data bits?" makes
>        sense'. 

IJ: I find this informal definition very problematic. First, the term
"textual equivalent" has not been defined yet, so I don't know that it
will be understood by a large audience (and even those closely
involved struggle over the definition of this term). Also, it's
not clear to me what "data-oriented" can be reduced to text.

Please clarify what is meant informally here.

> Data-centric schemata include both the interaction and
>        behavioral aspects of an XML application.
> 
> Metadata-oriented:
>        When  the  content  being  marked up is metadata. Examples: For
>        expressing  data processing (for example XSL - Extensible Style
>        Language),   RDF   (Resource   Description  Framework),  Schema
>        languages, etc.

IJ: The split is problematic since one person's metadata is another
person's data.
 
> According   to   this   taxonomy,   these   guidelines   only  address
> Data-oriented  schemata.  This  does  not  imply  that  there  are not
> accessibility  issues  or  features  in a Metadata-Oriented schemata -
> see,  for example, how XSLT, a component of XSL, can assist in Braille
> formatting.  Since they do not convey end-user oriented data, however,

IJ: "end-user oriented data" is much closer to what I would have
expected, but even that's somewhat problematic. For instance, in UAAG
1.0, we a consider style sheet that cause the color blue to appear to
be content meant for humans (even though 'color : blue' is never read
by humans, only by the machine).

> Metadata-Oriented schemata are out of the scope of these guidelines.
>   _________________________________________________________________
> 
> Problem statement
> 
> The  WAI (Web Accessibility Initiative) has done extensive work in the
> HTML area, resulting in lots of new functionalities being added to the
> version  4.0 of the language (see the HTML4 Accessibility Improvements
> paper).
> 
> These features includes:
>   * Improved structure (such as fieldset, optgroup in form)
>   * Support of separate Style Sheets
>   * Better alternate content (required alt, longdesc, caption, etc)
>   * Easier navigation (tabindex, link, etc)
> 
> One  area  of  concern  with  the advent of XML is that the freedom of
> design  it  bringshas  and  can  result  in  a  loss  of accessibility
> features,  present  today  because  of  HTML's  pervasive presence and
> widely available specification.
> 
> For  instance,  one could design a new XML language that would prevent

IJ: I think that "prevent" is too strong, notably since one might
still provide a secondary page for access. How about "make it much
more difficult?"

> the  creation of accessible documents, by not including in the element
> or  attribute set a way to attach an alternate textual description for
> a photo:
> <menu>New England Restaurant</menu>
> <appetizer>Clam Chowder
> <photo url="clam.jpg"/> <!-- no alt attribute or
> 			     textual content model here -->
> </appetizer>
> 
> In  this  example, the problem is not that the author of this document
> didn't  put  an  alt  attribute  or textual equivalent attached to the
> photo  element,  it's that the designer of the language didn't put the
> attribute  or  the  proper support in the language itself (that is, in
> the schema or the DTD).
> 
> But  let's  start  by  defining  what we mean by accessible schema and
> documents  (Details  on  these  definitions are provided at the end of
> this document):
>   * An  XML  schema  is  accessible if it enables, and indeed actively
>     promotes, the creation of accessible documents
>   * A  document  is  accessible if it can be equally understood by its
>     targeted audience regardless of the device used to access it.
>     An  accessible  document  is also defined as conforming to the Web
>     Content Accessibility Guidelines.

IJ: Please do not define an accessible document to be one that
conforms to WCAG. In all three WAI Guidelines, we have gone out of our
way to say that conformance DOES NOT equal accessibility. ATAG 1.0
says [1]:

   "There will also be authoring tools that produce accessible content
   in favorable circumstances (e.g., a text editor used by a motivated
   author), or provide an accessible interface to authors with certain
   disabilities, but that do not conform to these guidelines."

UAAG 1.0 says [2]:

   "Note: Conformance to the requirements of this document is expected
   to be a strong indicator of accessibility, but it is neither a
   necessary nor sufficient condition for ensuring the accessibility
   of software."

I would prefer that XMLAG (that seems to be the current short name for
this document) NOT rely on WCAG, otherwise the conformance
dependencies will be circular. I would like XMLAG to explain how to
build an XML format that supports accessibility. I would like WCAG to
require authors to use formats that conform to XMLAG (though WCAG will
also require more). I would like UAAG to require that developers
implement specs that conform to XMLAG. I imagine we will have more
discussions on this topic. In the development of UAAG 1.0, since we
did not have XMLAG, we require that developers implement
specifications that allow authors to conform to WCAG 1.0. But this is
an unnecessary indirection, I think.

[Please include references to all three WAI Guidelines in the
references section.]

[1] http://www.w3.org/TR/ATAG10/#Introduction
[2] http://www.w3.org/TR/UAAG10/conformance.html#Conformance
 
> As explained in the introduction, we're only considering Data-oriented
> languages  here,  and  for  them,  the  message  is  simple: be device
> independent and export your semantics as much as you can.
> 
> While  the  priority is stronger on the first aspect (multi-modality),
> both aspects are important, as without the knowledge of the meaning of
> the   XML  elements  and  attributes,  there  is  little  chance  that
> alternative  user  agents  can  do something intelligent with just the
> document bits.

IJ: As I read this I think that you need an introduction that explains
the expected processing model. The previous sentence would make more
sense if you explained how various user agents will interact, and some
things that an AT can do with semantically-rich content.
 
> This  semantics  knowledge  can  be  provided  through  human readable
> documentation  of  course,  but  having machine readable assertions of
> semantics  that  can  then  be used to present the document in various
> media  is  paramount  for  pervasive access (that is, you don't need a
> programmer, you just need a program). Enabling others to map from your
> language  to  existing  ones, or vice versa, is a useful accessibility
> feature.
> 
> ICADD  (International  Committee  on Accessible Document Design) was a
> pioneer  in  this  topic,  

IJ: Reference?

> for  SGML  accessibility and ways to convey
> arbitrary schema semantics (using specific SGML binding mechanisms). A
> few years later, ICADD has not really been adopted (in fact, the ICADD
> DTD was replaced by HTML and its well known semantics), and people are
> still trying to solve the same problem, albeit with more experience in
> the field of HTML accessibility, and applied to XML this time.
>   _________________________________________________________________
> 
> Guidelines for Designers of Data-oriented XML Tagsets
> 
> This  section  provides  a  list of four guidelines, which are general
> principles  of  accessible  design.  Guidelines  include rationale and
> checkpoints.  Each  checkpoint  expresses a requirement, includes some
> informative  text  about the checkpoint and one or several Techniques,
> where  implementations  and  examples of the checkpoint are discussed.
> Note that the checkpoints are not prioritized at that point.

IJ: I recommend that the structure of a guideline/checkpoint be
more formal, otherwise readers will have a hard time
distinguishing normative from informative parts. For instance, in
UAAG informative notes are identified as such. In XMLAG, there is
often an informative sentence or two after the checkpoint
text. If I were listening to the content, I would not know when
the informative material starts. Also, I think that it's useful
to distinguish rationale (i.e., why doing this helps people with
disabilities) from clarification of the checkpoint's intentions.

>   * Guideline  1.  Ensure  that  authors  can associate multiple media
>     objects as alternatives
>     Web  content  providers must able to offer alternative versions of

IJ: To avoid confusion about what is normative, I recommend not using
"must" outside of a checkpoint requirement.

>     their  content  if  they  wish  to  do  so  (as  the  Web  Content
>     Accessibility   Guidelines   tell   them   to   do   so).  Textual
>     alternatives,  for  instance, can be repurposed for many different
>     output devices, whereas non-textual content is often confined to a
>     certain   set  of  devices.  Thus,  by  allowing  and  encouraging
>     synchronized  textual  alternatives,  you  allow your tagset to be
>     more interoperable, and hence accessible.

IJ: The subject of the sentence shifts from "Web content developers"
to "you". [I prefer the impersonal form rather than "you".]
 
>      1.1 Provide a mechanism to explicitly associate alternative
> 	     equivalents for content or content fragments.

IJ: Can "alternative equivalent" be reduced to "alternative"? 
What is an alternative that is not equivalent? I might seek a 
job as a computer scientist or alternatively as a doctor. These
are alternative careers that I wouldn't try to qualify as being
equivalent. In the context of XMLAG, are there any alternatives that
are not intended to be equivalent? If always intended as equivalents,
I recommend shortening to "alternative".

> 	     Authors  using  the  elements/attributes in your language
> 	     must  have  the  ability  to provide alternatives for any
> 	     content,  be  it  images,  movies,  songs,  running text,
> 	     whatever.
> 
>      Techniques for 1.1
> 	     For  example, the summary and the caption elements in the
> 	     XHTML  table module can be used to provide a rich textual
> 	     description   of   a  non-textual  media.  cf.  WCAG  1.0
> 	     checkpoint 1.1.
> 
> <table border="1"
>     summary="This table gives some statistics about fruit
> 	     flies: average height and weight, and percentage
> 	     with red eyes (for both males and females).">
> <caption><em>Statistics</em> about fruit flies</caption>
> <tr><th rowspan="2"><th colspan="2">average
>    <th rowspan="2">red<br>eyes
> <tr><th>height<th>weight
> <tr><th>males<td>1.9<td>0.003<td>40%
> <tr><th>females<td>1.7<td>0.002<td>43%
> </table>
> 
>      1.2 Define flexible associations, where a given kind of
> 	     relationship can link to or from objects of varying
> 	     types.
> 	     By flexible, we mean so that it is not constrained by the
> 	     language  itself.

IJ: Rather than use "flexible", I recommend stating the part about
constraints in the checkpoint. The indirection will lead to 
confusion.

Furthermore, I think the requirement could be expressed more clearly,
but I don't have a proposal right now. I think that if the concept of
"alternative" is expanded on in checkpoint 1.1, then it may be reused
with more clarity in 1.2.. For instance, does 1.2 mean that
relationships between alternatives should be (1) explicit in markup,
not just in prose and (2) bi-directional? Add to this (3) allow rich
markup, (4) allow reuse, ...

> For example, HTML lets you add "alt" to
> 	     images,  but  it  does  not let you add images to runs of
> 	     text/markup,  so people have to put up with less adequate
> 	     mechanisms,  perhaps  by adding "see figure 1" at the end
> 	     of  a  paragraph.  If the content of <img> was other than
> 	     empty, this would have solved the problem to some extent.
> 	     Another  way  would  have  been  to  add  an  "appliesto"
> 	     attribute  to  the <img> element, allowing you to put the
> 	     associated  image  elsewhere  in the document. Satisfying
> 	     this  checkpoint  takes  a  lot  of  thought  due  to its
> 	     subjective  nature, but it's very important. For example,
> 	     if  <img>  were  non-empty,  or  if  it  had an appliesto
> 	     attribute,  it is probable that many more people would be
> 	     associating images with text/markup runs.
> 
>      Techniques for 1.2
> 	     In SVG, the desc element can be used to fully described a
> 	     graphic,  using  structured  text from a different tagset
> 	     for instance, and in the graphics itself, the description
> 	     text can be reused.
> 
> <svg xmlns="http://www.w3.org/2000/svg" xml:lang="en">
> <g>
>     <desc xmlns:mydoc="http://example.org/mydoc">
>        <mydoc:title id="title1">The sales bar chart by region</mydoc:title>
>        <mydoc:para>This description uses markup from the
>        <mydoc:emph>mydoc</mydoc:emph> namespace.</mydoc:para>
>     </desc>
>        <!-- now the picture which includes text referencing the description
> -->
>      <rect x="10" y="20" ...>
>      <text x="100" y="200" font-size="15" fill="red" >
> 	<tref xlink:href="#title1"/>
>      </text>
> </g>
> </svg>
> 
>      1.3 Reuse existing accessible modules to indicate
> 	     alternative-equivalent associations.

IJ: I think I prefer might be "accessibility modules" to
"accessible modules". I think it might be useful to preface
the requirement a little with something like:
   "When building a format out of smaller modules, reuse 
    proven accessibility modules."

Why would one only be interested in reuse of modules related to
alternative equivalents? Are there other functionalities that benefit
accessibility (e.g., metadata) that might be reusable?

> 	     Reusing  accessible modules has the advantage of assuring
> 	     that  your  "customers"  can  be confident that materials
> 	     produced  using your language will be accessible to their
> 	     clients.  No  need to create "new" elements/attributes or
> 	     re-invent   the  wheel  just  to  satisfy  some  creative
> 	     fantasy.  There's a non negligeable cost for your authors
> 	     (the people using your language) to learn new concepts.
> 
>      Techniques for 1.3
> 	     This example shows how to use an existing DTD module: the
> 	     object from the XHTML tagset
> 
> <!DOCTYPE document SYSTEM "myDTD.dtd" [
>  <!ENTITY % qnames
>       PUBLIC "-//W3C//ENTITIES XHTML Qualified Names 1.0//EN"
> 	     "xhtml-qname-1.mod" >
>  <!ENTITY % object
>       PUBLIC "-//W3C//ELEMENTS XHTML Embedded Object 1.0//EN"
> 	     "xhtml-object-1.mod" >
>  %qnames;
>  %object;
>  ]>
> <i:inventory xmlns:i="http://www.my.org/xmlns/inventory">
> <i:stockitem>
>  etc.
> <xhtml:object...>
>  to include a picture or movie of the part.
> 
>   * Guideline 2. Create semantically-rich languages

>     Data-oriented  XML  should contain precise methods of encoding the
>     data for its particular scope. By increasing the semantics of your
>     tagset,  and  setting  linking devices to outside presentations or
>     further  semantics,  you  allow  your data to become "Webized" and
>     hence to operate within many environments.

IJ: I think that the term "semantically-rich" needs more
explanation. For instance, HTML is rich in presentation semantics
(not really, but it's got presentation markup built-in). What
semantics are "good semantics" in terms of accessibility? Perhaps
that will be explained via the checkpoints below, but it would be
nice to have a model in my head as I go to read them.
 
>      2.1 Ensure all semantics are captured in markup in a
> 	     repurposeable form.
> 	     In  general,  languages must be designed so that they can
> 	     be  presented in a device independent way. 

IJ: That's the sentence I was looking for. Can it be moved up
to the intro paragraph?

Similarly, "repurposeable form" doesn't satisfy me because I
don't know what the reference is. Repurposable with respect to
what? Probably input and output devices, and but there are other
axes as well such as spatially independent (don't make the user
have to use a mouse), temporally independent (don't require input
within a finite time interval), etc.

>Languages used
> 	     only  for  presentation to a certain scope of users (that
> 	     is,  final  form  tagsets) should adhere to the following
> 	     caveats:
> 
> 	    o They  should  not  be  promoted  as  being  a  generally
> 	      suitable  method  of  storing  content  that can be used
> 	      across a variety of devices.
> 	    o The  server  should  make  sure  the  client  wants this
> 	      particular form before serving it.
> 	    o They  should  allow  the  authors to associate the final
> 	      form  with  the  higher  level  semantics of the source,
> 	      whenever applicable.

IJ: I suggest making this a separate checkpoint (or part of 2.1),
as in:

 2.x A format that represents information in a "final form" 
 that is device-dependent must:
    a) allow the author to associate instances of the format
       with source documents that are more semantically rich,
    b) not be served without confirmation from the client
    c) not be promoted as a suitable method of storing
       information in a device-independent manner.

I think that it's probably a good idea to group checkpoints
according to their subject. For example:

  1) An XML format must ... (most of the checkpoints in this
     document). This can also be turned into "a developer of
     a format must", but I don't think that's necessary. In UAAG
     we say "a user agent must" and not "a UA developer must..."

  2) An server of this format must ... (e.g., part of 2.1)

  3) The create of the format must ... (e.g., checkpoint 3.1,
     since it's about a default style sheet for the format, and
     less about the elements of the format. I don't know whether
     this distinction is useful: DTD/Schema-level requirements 
     versus specification-level requirements such as the default
     style sheet.)
 
>      Techniques for 2.1
> 	     See  the  last  paragraph of the XSL 1.1.1 section for an
> 	     example of such wording.
> 
>      2.2 Separate presentation properties using stylesheet
> 	     technology/styling mechanisms.
> 	     Authors  must  be  able  to mark up documents with proper
> 	     structural  elements  and control presentation with style
> 	     sheets   rather   than  with  presentation  elements  and
> 	     attributes.  This separation of content from presentation
> 	     facilitates   the  adaptation  to  users  with  different
> 	     presentational  needs (larger font, better contrast, etc)
> 	     and it also facilitates the maintenance of the
>            pages.
>      Techniques for 2.2
> 	     Example: Wrong
> 
> 	     Do  not include presentational attributes and elements in
> 	     your language.
> 
> <p align="center" font="arial" weight="bold">News items 1</p>
> <p align="center" font="arial" weight="bold">News items 2</p>
> <p align="center" font="arial" weight="bold">News items 3</p>
> 
> 	     Example: Right
> 
> 	     Support  the  inclusion  and processing of external style
> 	     sheets.
> 
> mystyle.css: .news { text-align: center; font: bold arial }
> 
> <?xml-stylesheet href="mystyle.css" type="text/css"?>
> <p class="news">News items 1</p>
> <p class="news">News items 2</p>
> <p class="news">News items 3</p>

IJ: As I understand the benefits of style sheets:

   a) Most of the benefits are for authors (e.g., factorization,
      reuse, caching, performance improvements, etc.).
   b) The primary (only?) user benefit is the ability to override
      author-specified styles. CSS builds this in. XSL does not.

I don't think that the example shown is that relevant
(other than it shows style sheets) because it doesn't say
how the user can override the authors' styles.
 
>      2.3 Use the standard XML linking and pointing mechanisms (XLink
> 	     and XPointer).
> 	     XLink  and  XPointer have been reviewed for accessibility
> 	     and provide known linking and pointing mechanisms.

IJ: Change "and provide known linking and pointing mechanisms" to
"and their linking/pointing semantics may be recognized with certainty."
 
>      Techniques for 2.3
> 	     Example. Wrong
> 
> 	     User Agents have no way of knowing this is a link.
> 
> <mylink
> linkend="http://mysite/myfile.xml">
>  Current list of references
> </mylink>
> 
> 	     Example: Right
> 
> 	     Links can be recognized reliably by XLink
> applications.

IJ: Yes, that's what I mean.
 
> <crossref xmlns:xlink="http://www.w3.org/1999/xlink"
>  xlink:href="http://mysite/myfile.xml">
>  Current list of references
> </crossref>
> 
>      2.4 Define element types that allow classification and grouping
> 	     (header, section, list, etc).
> 	     Make  use of existing mechanisms (noting checkpoint 1.2),
> 	     or   create   them   where   necessary,  following  these
> 	     guidelines.  Ensure  that  elements are present which can
> 	     then be used for classification and grouping.

IJ: Delete the sentence starting with "Ensure" (I don't think it
adds any information). I think the previous sentence can be
reduced to a cross reference to a general reuse checkpoint.
 
>      Techniques for 2.4
> 	     Think  about the overall structure of your documents when
> 	     you design a tagset.

IJ: I don't think that the previous sentence is very useful.
Format designers always think about what they are doing. They may
not think about it the way you want them to. What do you want
them to think about?


> <-- menu - highest level block element
>   appetizer - first child of section, major block element
>   entree - second child of section, major block element
>   entity meal-sequence - common paragraph level blocks -->
> <!ELEMENT menu (title , ((%meal-sequence;)|  appetizer)+)>
> <!ELEMENT appetizer (title? , ((%meal-sequence;) | entree)+)>
> 
>      2.5 Provide for a full containment model with chunks of
> 	     reasonable size.
> 	     If  a document instance is fully contained, i.e. adequate
> 	     wrapper  elements  around  PCDATA, then both CSS and XSLT
> 	     can   be  used  to  style  content  for  presentation  in
> 	     alternate  formats.  If  content  is  in reasonable sized
> 	     containers, it enables the document to be skimmed quickly
> 	     by  non-  visual  readers.  If  a  logical  hierarchy  of
> 	     elements is used, then a table of contents or summary may
> 	     be   generated   providing  logical  access  to  document
> 	     content.

IJ: This checkpoint is hard to understand. I'm not sure I
understand what a full containment model is. Also, please try to
be more specific than "chunks of a reasonable size." 

If I understand, there is an art to designing a format so that
there is "just enough markup in just the right places." You don't
want long stretches of text without any surrounding structure.
And you don't want to require the author to use tags left and
right (I don't know whether a million tags always benefits ATs
either, but I don't have data to back that up). If this is the
thrust of the checkpoint, I think it could be clearer.

Do you have any advice about the accessibility issues around
mixed content models?
 
>      Techniques for 2.5
> 	     In  this XML Schema example, a document is broken up into
> 	     a number of sections, and a sequence of nestable sections
> 	     with   a  consistent  structure  may  be  used  for  both
> 	     navigation  and  the  automated  generation of a table of
> 	     contents to whatever level.
> 
> <xsd:schema xmlns="http://www.publishing.org"
>   xmlns:xsd="http://www.w3.org/2000/10/XMLSchema">
>  <xsd:element name="document">
>      <xsd:complexType>
> 	 <xsd:sequence>
> 	     <xsd:element ref="head"/>
> 	     <xsd:element ref="section"/>
> 	 </xsd:sequence>
>      </xsd:complexType>
>   </xsd:element>
>   <xsd:element name="head" type="xsd:string">
>    <xsd:annotation>
>       <xsd:documentation>Section title</xsd:documentation>
>    </xsd:annotation>
>   </xsd:element>
>   <xsd:element name="section">
>      <xsd:complexType>
> 	 <xsd:sequence>
> 	     <xsd:element ref="head"/>
> 	     <xsd:element ref="section"/>
> 	     <xsd:element ref="paragraph" maxOccurs="unbounded"/>
> 	 </xsd:sequence>
>      </xsd:complexType>
> </xsd:element>
>   <xsd:element name="paragraph" type="xsd:string"/>
> </xsd:schema>
> 
>      2.6 Define element types that identify important text content.
> 	     Within  most  documents,  certain elements are key to its
> 	     understanding.  If  these  are both clear, and identified
> 	     for  machine  access, their content can be presented to a
> 	     user  to  gain  a swift understanding of the semantics of
> 	     the  element,  section and eventually the whole document.


IJ: I'm not sure that "important" will be helpful to
designers. In UAAG 1.0, checkpoint 2.3, we decided that we would
gain more by being more specific, so we refer to "summary, title,
alternative, description, or expansion of another piece of
content". In 9.9, we do refer to "navigation of important
structural elements". This kind of vague requirement should be
made with caution (though I'm happy that there is consistency
between UAAG and XMLAG language). Here's an attempt to state 
when content is *important to accessibility*.

   a) A piece of content A is important if the semantics of the
   format explicitly designate it as important. For instance, in
   HTML, <strong> and <em> call out the fact that some content is
   important. Of course, a <table> may be very important, but the
   semantics of importance are not part of the specification.

   b) Content A is important if it would allow a user to
   understand another piece of content B more quickly. Thus,
   titles, summaries, and descriptions are important.

   Note: These things are important to *accessibility* for
   reasons of orientation. Content may be important for
   other reasons (e.g., tables are important for associating
   data).

   c) Content A is important to accessibility if it is
   identified by specification to be an accessibility feature.

These are just some ideas on being more specific about what
is important.

> 	     Examples  of  such important elements are numbers, dates,
> 	     titles and links.
> 
>      Techniques for 2.6
> 	     Mark  up  your  text  with more semantics, such as saying
> 	     "this is a date", or "this is an acronym".

IJ: This is confusing. It sounds like the author should be using
those English words. Rather: "Use markup for datatypes where
available."

> 	     Code  example:  Using the XML schema language to identify
> 	     data types, rather than simply leaving them as strings: a
> 	     fully constrained ISBN number:
> 
> <xsd:simpleType name="ISBN-Type">
>  <xsd:restriction base="xsd:string">
>      <xsd:pattern value="\d{5}-\d{5}-\d{5}"/>
>      <xsd:pattern value="\d{1}-\d{3}-\d{5}-\d{1}"/>
>      <xsd:pattern value="\d{1}-\d{2}-\d{6}-\d{1}"/>
>  </xsd:restriction>
> </xsd:simpleType>
> 
>      2.7 Provide a mechanism for identifying summary / abstract /
> 	     title.

IJ: I think this checkpoint is more helpful since more specific.
Can it be combined with 2.6?

> 	     Knowing how to extract that information allow User Agents
> 	     to present it to the end-user, thus facilitating browsing
> 	     of  the  content (e.g. deciding if yes or no the document
> 	     is of interest).
> 
>      Techniques for 2.7
> 	     Example:  XML  using  RDF  and  Dublin  Core  well  known
> 	     semantics.
> 
> <someElement xmlns="http://xmlns.com/example">
> <rdf:RDF
>  xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
>  xmlns:dc="http://purl.org/dc/elements/1.1/">
>  <rdf:Description about="http://www.dlib.org/">
>    <dc:Title>
>        D-Lib Program - Research in Digital Libraries
>    </dc:Title>
>    <dc:Description>The D-Lib program supports the community of
>     people with research interests in digital libraries and
>     electronic publishing.</dc:Description>
>    <dc:Publisher>
>        Corporation For National Research Initiatives
>    </dc:Publisher>
>    <dc:Date>1995-01-07</dc:Date>
>    <dc:Type>World Wide Web Home Page</dc:Type>
>    <dc:Format>text/html</dc:Format>
>    <dc:Language>en</dc:Language>
>  </rdf:Description>
> </rdf:RDF>
> <!-- .....other xml.... -->
> </someElement>
> 
>      2.8 Don't overload the semantics of individual elements.

IJ: Change "individual elements" to "each element type." And use
"element type" instead of "element name" below. [I may be wrong
here - perhaps "element name" is correct, in which case it should
be used consistently.]

> 	     If an element name may be confused, within the context of
> 	     the  document instance, then it is said to be overloaded.
> 	     If  each  element  name  is  unique  within context
> it is

IJ: What does "within context" mean and what is the relation to
namespaces?

> 	     easier   to  access  the  document  semantics.  Note  the
> 	     relation to checkpoint 4.9.
> 
>      Techniques for 2.8
> 	     Example: Wrong
> 
> <report>
> <invoice>
>  <amount>25 dollars</amount>
>  ....
>  </invoice>
> <description>
> <item>Widgets</item>
> <amount>25</amount>
> </description>
> </report>
> 
> 	     In the example above, the designer of the schema intended
> 	     the  first  occurrence  of  the  element "amount" to mean
> 	     'price'   of   the  products  purchased  and  the  second
> 	     occurrence to mean 'quantity' of the products purchased.
> 
> 	     Example: Right

IJ: I think I prefer "Incorrect example" and "Example", and it's
probably better to put the "Example" before the "Incorrect
Example" as much as possible -- that way people arrive at the
right thing to do first.
 
> <report>
> <invoice>
>  <price>25</price>
>  <currency>Dollar</currency>
>  ....
> </invoice>
> <description>
> <item>Widgets</item>
> <quantity>25</quantity>
> </description>
> </report>
> 
> 	     In  the example above, the meaning of all the elements is
> 	     clear and none of the individuals elements is overloaded.
> 
>      2.9 Reuse accessible modules from schemata as originally
> 	     specified / intended.
> 	     When using modules from other schemata, use them with the
> 	     same semantics as originally intended.

IJ: I suggest merging this checkpoint with 1.3: "Reuse modules,
and reuse them appropriately."
 
>      Techniques for 2.9
> 	     Example: reusing SMIL switch
> 
> ...
> <par>
>  <video src="anchor.mpg" ... />
>  <switch>
>    <audio src="HiQuality.wav" systemBitrate="56000" ... />
>    <audio src="MedQuality.wav" systemBitrate="28800" ... />
>    <audio src="LowQuality.wav" ... />
>  </switch>
> </par>
> 
>      2.10 Allow association of metadata with distinct elements and
> 	     groups of elements.
> 	     This   permits   authors   to  make  even  more  semantic
> 	     associations  than  what  was  originally intended by the
> 	     language designer.

IJ: There are several options here:
  1) The author has metadata associated with some content A, and 
    the content A is unaffected.

  2) The author references the metadata from A (so A "knows about
    it").

  3) The author includes the metadata directly in A.

Which mechanisms does 2.10 mean to address? From the prose
description, I understood 3 only. 
 
>      Techniques for 2.10
> 	     In  SVG  for  instance, there is a metadata element where
> 	     RDF  statements  can  be  declared, pointing at graphical
> 	     elements and adding more relational semantics (one object
> 	     linked  to  another,  or  on top of another) than what is
> 	     provided  by  SVG  itself. See the SVG Accessibility note
> 	     for examples.

IJ: Please include the SVG Accessibility Note in the references
sections.
 
>   * Guideline 3. Design an accessible user interface.
>     Web  content  is  rapidly  shifting  from  static pages to dynamic
>     pages,  called  Web  applications. This is most often done using a
>     scripting language based on event callback. The language designers
>     must  ensure  that the model they chose allows for user control of
>     presentation.  Always  ensure  that  nothing in the presentational
>     aspect  of  the  document attempts to restrict user control of how
>     the document instance is accessed.

IJ: Much of the previous paragraph sounds like a list of
requirements, rather than rationale that explains the
accessibility issues.
 
>      3.1 Provide default style sheets for multiple output modalities
> 	     where possible.
>
> 	     The additional effort from the language designer point of
> 	     view  in providing stylesheets which can represent an XML
> 	     document  instance in alternate modalities is minimal and
> 	     will  have a multiplier benefit for all the authors using
> 	     the  language  and  these  style  sheets. Readers of your
> 	     documents  may  prefer  audio  access,  so  providing  an
> 	     appropriate  stylesheet with your schema which will allow
> 	     those  readers  to  utilise synthetic speech to produce a
> 	     clear rendering of the content.
> 
>      Techniques for 3.1
> 	     Example: See the sample style sheet for HTML 4.0 provided
> 	     with the CSS2 spec,
> 
>      3.2 Define navigable structures that allow discrete, sequential,
> 	     structured, and search navigation functionalities.
> 	     Navigable  structures  are  the  key  elements  used  for
> 	     navigation  around  an  XML  application.  Define element
> 	     types  that  allow classification and grouping, or re-use
> 	     existing accessible grouping and classification modules.
> 
>      Techniques for 3.2
> 	     Example:  See  how  the Digital Talking Book DTD provides
> 	     elements for navigable structures.

IJ: I think that you'll need to explain the different navigation
functionalities in more detail (e.g., discrete v. sequential).
 
>      3.3 Use CSS or XSLT to describe a basic outline view.

IJ: Presumably, the outline view will be based in part on some of
the "important" elements (or more specifically "title"-like
elements) discussed in earlier checkpoints. I recommend a cross
reference and harmonization of the terms/expressions used to
describe the elements.

> 	     The  language  designer  is  the best placed to provide a
> 	     mapping of the new language constructs to a basic outline
> 	     format,  which  will facilitate the deployment of content
> 	     by making it understandable for all classes of users.
> 
>      Techniques for 3.3
> 
> <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
> 	     version="1.0">
> <xsl:output method="html"/>
> <xsl:template match="/">
> <html>
> <head>
> <title>Outline of x</title>
> <body>
> <-- This provides the link back to the full source document -->
> <a href="source.xml">full source of document</a>
> <h3>Outline view</h3>
> <p>  <xsl:for-each select="//section">
>    <xsl:number level="multiple" count="section" format="1.1.1"/>
>    <xsl:value-of select="title"/>
>    <br />
> </xsl:for-each>
> </p>
> <xsl:apply-templates/>
> </body>
> </html>
> </xsl:template>
> <xsl:template match="*"/>
> </xsl:stylesheet>
> 
>      3.4 Use a device-independent interaction and events model /
> 	     module.
> 	     Any  XML  application which contains user interaction may
> 	     exclude  readership  if  presumptions  are made about the
> 	     technology  used to access that application. What happens
> 	     when  the application only support mouse interaction, and
> 	     the  user  is  not  mouse bound? 

IJ: I don't recommend asking a rhetorical question here, but
explaining the issues to the reader.

> The result could be lost
> 	     sales,  it  will  be  a loss of interest and a search for
> 	     alternatives.
> 
>      Techniques for 3.4
> 	     Using DOM2 event the right way in SVG.
> 
> <script> function DoOnActivate(evt) { .. } </script>
> 
> <g onactivate="DoOnActivate(evt)">
> <rect id="button" x="500" y="500" width="250" height="40"/>
> </g>
> 
>      3.5 Allow for user control of interaction timing - rate of
> 	     change, external events triggering document changes,
> etc.

IJ: I think this checkpoint needs more work. It's not clear
what "interation timing" means. There are a lot of technical
details like: events that are synchronized with the wall clock,
events that are driven by the user, events that are synchronized
relative to other presentation events, etc. I think more
explanation is required.

> 	     If an XML application presumes that all readers will take
> 	     in content in a fixed time period, will read at a certain
> 	     rate, or access each page in a certain time, then readers
> 	     and  users  of  that application will be lost. We each do
> 	     things in our own time, and dislike being dictated to.
> 
>      Techniques for 3.5
> 	     Ensure  and  promote the work the user agent has to do to
> 	     control  - on behalf of the end-user - the rate of change
> 	     of  content presentation, perhaps using element attribute
> 	     for  pause  facility  orr settable rate to allow the user
> 	     control  of all interactions. Fixed time period time-outs
> 	     are not popular. See the SMIL-Animation specification for
> 	     examples of such design.
> 
>   * Guideline 4 Document and export semantics
>     Make  sure  that  all people can understand your design and
> map to and  from  your  elements,  and easily make assertions
> about them.

IJ: I don't think that you can guarantee that all people will
understand something. Also, I'm not sure what mapping to
and from means. Please clarify the intent of this first sentence.

>     Furthermore,  make  sure  that  you  provide  your own first party
>     assertions  about  your  languages:  for example, don't make users
>     guess an element's purpose.
> 
>      4.1 Ensure human-readable documentation conforms to WCAG double
> 	     A.
> 	     Everybody  should  be  able  to  read  and  understand  a
> 	     technical specification, even one that is purely intended
> 	     for a particular class of users.

IJ: I think it's overstating the issue to say that "everyone
should be able to understand a technical spec." I think that it's
one thing to write a document clearly for a particular audience,
and it's another to write related material for different
audiences. I don't think that XMLAG should set the expectation
that every piece of documentation must be usable by every person.
It may be sufficient to say "Write clearly, and provide materials
for different audiences and different reading skills." 

By the way, the sentence (which is about comprehension) doesn't
line up with the requirement (which is about accessibility).
 
>      Techniques for 4.1
> 	     For  instance,  blind  users routinely author Web content
> 	     that  is  intended  for sighted users, and they can do so
> 	     because   the   HTML   and  the  CSS  specifications  are
> 	     accessible  (well  structured,  description  of pictures,
> 	     etc).

IJ: Hey, thanks! <grin>
 
>      4.2 Provide a machine-understandable means/mechanism to get from
> 	     a document instance to the schema.

IJ: What about DTDs? 

How about 

   "4.2 Provide a machine-understandable means/mechanism
        to retrieve the formal grammar (e.g., schema or DTD)
        used to structure content."

I wanted to say "identify" instead of "retrieve", but the
next sentence explicitly mentions automatic retrieval. It
may be good to require 'identification' of the formal grammar
in either a machine-readable or human-readable form. And 
machine-readable form for automatic retrieval.

> 	     This   allows  programs  to  automatically  retrieve  the
> 	     documentation of a language.
> 
>      Techniques for 4.2
> 	     Example:  Uses the W3C XML Schema language as the schema,
> 	     referencing it via the xsi:schemaLocation attribute.
> 
> <?xml version="1.0" encoding="utf-8"?>
> <my:doc
>  xmlns:xsi="http://www.w3.org/2000/10/XMLSchema-instance"
>  xsi:schemaLocation="http://www.example.org/schemas/doc.xsd"
>  xmlns:my="http://www.jenitennison.com/"
>  xmlns="http://www.w3.org/1999/xhtml">
> 
>      4.3 Provide explicit human readable definitions for markup
> 	     semantics.

IJ: I'm not sure what this checkpoint means. Does this mean
"Write documentation?" If the format developer writes no
documentation, the format will probably be useless (or at least
not easy to use). Does this mean "Write human-readable, not just
machine-readable" documentation? Does this mean "Write *good
documentation* where the semantics of each element is made
explicit?"

> 	     Any  schema  which  is  designed  by a single person in a
> 	     reasonable  period

IJ: What does "in a reasonable period" mean?

>             will only be understood by that person
> 	     designing   it.   When   exposed   to  document  authors,
> 	     interpretations  will vary. If the schema designer wishes
> 	     document authors to utilise the same semantics then those
> 	     semantics  require  documentation. The better the quality
> 	     of   that  documentation,  the  more  likely  the  shared
> 	     understanding.
> 
>      Techniques for 4.3
> 	     Example: TREX
> 
> <element name="paragraph">
>  <xsd:annotation>the lowest level block container.</xsd:annotation>
>  <empty/>
> </element>
> 
>      4.4 Use schema (in preference to DTD) to provide explicit
> 	     documentation/annotation of element/attribute/etc
> 	     semantics.

IJ: Use "schemas" or "schema"? Can 4.3 and 4.4 be merged?
It sounds like 4.4 supersedes 4.3 the way they are written.

> 	     Schema  allows the language designer to explicitly attach
> 	     documentation  to elements and attributes, thereby making
> 	     the language more understandable.
> 
>      Techniques for 4.4
> 	     Example:  The  need  for  the  head  element  is  clearly
> 	     described.
> 
> <xsd:element name="head" type="xsd:string">
> <xsd:annotation>
>  <xsd:documentation xml:lang="en-US">Title of the section.
>      Required for table of contents generation.
>  </xsd:documentation>
> </xsd:annotation>
> </xsd:element>
> 
>      4.5 Provide semantic relationships to other schemata where
> 	     appropriate and possible.

IJ: Pick one form and stick to it (schemas/schemata). [Maybe you
already do. This just occurred to me as a thing to watch for.]

I'm not sure what "provide semantic relationships" means. 

Does this checkpoint mean: "When you create a schema, you should
think about explaining how it relates to other schemas
(preferably expressing the relationships with a machine-readable
format)." Or does the checkpoint mean: "You will benefit the
world by showing how different schemas relate." When the
checkpoint says "to other schemata", you mean other than what?

> 	     This allows the authors using the language to reuse their
> 	     existing knowledge and tools.
> 
>      Techniques for 4.5
> 	     This can be done implicitly via subclassing/derivation of
> 	     existing  types,  by  asserting equivalence of type (e.g.
> 	     SVG  title  and  SMIL  title) or by mapping to well known
> 	     semantics.
> 	     Example:   mapping  the  Menu  example  provided  in  the
> 	     Introduction to XHTML using XSLT:
> 
> <html xsl:version="1.0"
>    xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
>    xmlns="http://www.w3.org/1999/xhtml>
> <head>
> <title>Mapping of language MenuML to html</title>
> <body>    <h1>Menu of: <xsl:value-of select="menu/"/></h1>
>  <h2>Appetizer: <xsl:value-of select="menu/appetizer/"/></h2>
> etc...
> </body>
> </html>
> 
>      4.6 Document accessibility features of the application.
> 	     This  is  useful  in  order  to foster the development of
> 	     state  of  the art assistive technologies to identify all
> 	     the  features  of  a  new  language  that  make  it  more
> 	     accessible.
> 
>      Techniques for 4.6
> 	     SVG  has  provided a good example of this being a part of
> 	     the  recommendation.  For W3C Working drafts, include and
> 	     document  those  specific  features  which positively aid
> 	     accessibility.
> 
>      4.7 Include accessibility requirements in conformance
> 	     requirements
> 	     This  promotes  the  development of accessible content in
> 	     the community caring about conformance.
> 
>      Techniques for 4.7
> 	     SVG  has specific accessibility requirements as a part of
> 	     the  overall  requirement document. When the requirements
> 	     are  drawn up, specific clauses need to be included which
> 	     clearly state accessibility requirements
> 
>      4.8 Document techniques for WCAG, ATAG, and UAAG with respect to
> 	     the XML application.

I recommend instead: "In the format documentation, explain how
the requirements of WCAG, ATAG, UAAG, and XMLAG apply to the
format." My only concern is that if XMLAG refers to UAAG etc.,
this may create a circular dependency. I'll have to think about
this.

> 	     The  WAI  suite  of accessibility guidelines (WCAG, ATAG,
> 	     and  UAAG)  contain  detailed  descriptions  as to how to
> 	     satisfy    each   individual   document's   requirements.
> 	     Therefore, it is important to review your XML application
> 	     to  ensure that you have implemented a relevant technique
> 	     for  each  checkpoint  in  the WAI suite of accessibility
> 	     guidelines.   For   example,   you   could   show  how  a
> 	     (hypothetical)  instance  of your application conforms to
> 	     WCAG,   how  an  authoring  tool  which  implements  your
> 	     application  would  enable an author to create accessible
> 	     content;  how  a  user  agent  capable of supporting your
> 	     application must conform to UAAG, etc.
> 
>      Techniques for 4.8
> 	     Still  using  the  MenuML  language, here are examples of
> 	     WCAG techniques
> 
> 	    o WCAG checkpoint 1.1: Provide a text equivalent for every
> 	      non-text element
> 	      MenuML  technique:  use the content of the photo element
> 	      to indicate the textual equivalent of the picture.
> 	    o WCAG  checkpoint  3.5:  Use  header  elements  to convey
> 	      document   structure   and   use   them   according   to
> 	      specification.
> 	      MenuML technique: use the appetizer element to introduce
> 	      a new appetizer, not a para and some bigger font
> 
>      4.9 Do not assume that element or attribute names provide any
> 	     information about element semantics.

IJ: To whom is this checkpoint addressed? Who should not assume
this? The user of the format spec (whether author or tool
developer)? Please clarify this (possibly grouping this
checkpoint with others related to format consumers).

> 	     An  element named may have a fully contextualized meaning
> 	     for  the schema author, but is unlikely to mean much to a
> 	     non-English  speaker.  Equally,  taken  out  of  context,
> 	     without  semantic  explanation,  element names often lose
> 	     their  meaning. Simply naming an element is not enough to
> 	     assure that document authors will utilise that element in
> 	     semantic  conformance  with the schema authors intent. It
> 	     is likely that confusion and misinterpretation will arise
> 	     if element or attribute names are relied upon to document
> 	     a schema.
> 
>      Techniques for 4.9
> 	     For example, using TREX, avoid colloquial element names.
> 
> 	     Example: Wrong
> 
> <element name="paragraph">
>  <xsd:annotation>
>  <xsd:documentation>paragraph</xsd:documentation>
>  </xsd:annotation>
>  <empty/>
> </element>
> 
> 	     Here  the  element  name  has  been  described  using the
> 	     element name only, which adds no semantic value.
> 
> 	     Example: Right
> 
> <element name="paragraph">
>  <xsd:annotation>
>  <xsd:documentation>The lowest level block container.
>  </xsd:documentation>
>  </xsd:annotation>
>  <empty/>
> </element>
> 
> 	     Here  the element name has been described in an alternate
> 	     form to clarify semantics rather than re-enforce the name
> 	     by repeating it.
> 
>      4.10 Document navigable structures. Describe how discrete,
> 	     sequential, structured, and search navigation mechanisms
> 	     should work
> 	     In order to navigate around a significant document, it is
> 	     helpful  to  the  reader  if  they know what elements are
> 	     available for such navigation.
> 
>      Techniques for 4.10
> 	     Random  access  to  any part of a document via a detailed
> 	     table   of  contents,  numbered  headings  which  may  be
> 	     searched for, a hierarchical view enabling fast access to
> 	     sought parts, and a search capability aid in this.
>   _________________________________________________________________
> 
> Appendices
> 
> Appendix A: Techniques Rationale
> 
> In  the  presentation  of  guidelines for XML accessibility, we try to
> separate  abstract  guidelines  from  implementation  techniques. This
> allows  us  to  talk  about  the  general guideline principles without
> spending the time up-front to solve the implementation issues.
> 
> In  fact,  there  are several techniques for achieving the same result
> and people's decision will be a function of time and product available
> and their own commitment to access.
> 
> For  instance,  if  an XML designer want to create some kind of "list"
> element  in  a  given  markup,  this  can be implemented using various
> techniques:
>   * using  the XHTML namespace and its [INS: elements :INS] (xhtml:ul,
>     xhtml:li)
>   * invent new constructs but provide an XSLT binding (to a HTML UL/LI
>     pair of element)
>   * using  XML/RDF  schemata  (if  a  list  primitive is available; or
>     through a new schema if a primitive is unavailable)
>   * using Architectural forms with support for list semantics
>   * etc
> 
> Appendix B: XML Accessibility Definitions
> 
>   * Schema: Even though we use the term "schema", we don't want people
>     to  assume  we  are  only talking about a schema as defined in XML
>     Schema  but  rather some document or collection of documents which
>     contains  all  the references for interpreting a document which is
>     encoded  in  accordance  with  the  usage  of  some application or
>     community  of  discourse. "Profile" might be a better word for our
>     usage.
>   * An  XML  schema  is accessible if it enables and actively promotes
>     the creation of accessible documents
>   * A  document  is  accessible if it can be equally understood by its
>     targeted audience regardless of the device used to access it.
>     An  accessible  document  is also defined by conforming to the Web
>     Content Accessibility Guidelines.

IJ: I don't think these definitions work. I prefer not talking
about "what is accessible", but instead "what conforms to this
document". This document promotes accessibility, by meeting known
user needs. I think you should delete the definitions and just
refer to conformance.
 
>   * The  word  "promote" is important as "enable" alone does not cover
>     the   case   where   a  schema  could  include  some  open  string
>     representation somewhere and claim minimal accessibility.
>     To  take  an example, suppose HTML didn't have an ALT attribute on
>     IMG,  it would still in theory "enable" the creation of accessible
>     documents,  since  HTML  files carry textual content and one could
>     always  describe  images inline, as in: <IMG SRC="Tax.gif"> How to
>     pay  your  taxes  but this doesn't "promote" accessibility as most
>     authors  will  not  want  to repeat "How to pay your taxes" if the
>     logo  already says "How to pay your taxes" (assuming CSS cannot be
>     used  for  that  instead  of  a  bitmap). Having the ALT attribute
>     "promotes"  accessibility  as  it  allows  images  to be described
>     without performance loss - such as duplication - for image viewer.
>     In  any case, accessibility is not just about alternative content,
>     as the next section will show.
>   * The  word  "device"  is also important as it encompasses more than
>     just  media  independence:  it's  both  output  (graphical, voice,
>     braille,  text-only)  and  input  (mouse, keyboard, voice, keypad,
>     one-touch).
>     This  term  also potentially carries with it the issues related to
>     high  bandwidth  availability  (or  lack thereof), where access to
>     data  becomes  impossible  on  slow  connection  because  of their
>     volume.
>   * The term "equal understanding" is critical as it permits some form
>     of  graceful  transformation  when presenting in one media content
>     primarily designed for another media.
>     Graceful   transformation   is  a  key  concept  in  the  area  of
>     accessibility. Let's define it.

IJ: Don't say "Let's define it". Just define it.

Also, the term graceful transformation doesn't appear elsewhere
in the document. I recommend avoiding it if you can. The document
already talks specifically about device-independence. Is that
sufficient?

I don't think "graceful transformation" is a bad concept, but if
you don't use it, it seems best to not define it.

>     Definition:
>     Graceful  transformation  is a property of a system that can still
>     function  relatively error free when the system is damaged or when
>     the  input  stimuli  are  incomplete.  In such systems, removing a
>     symbol token only results in the loss of the information stored in
>     that  token,  with  no  abrupt  performance decline of the overall
>     process.
>     For instance, suppose I need to check the online yellow line train
>     schedule  and  I don't have visual access to the Web. If the train
>     Web  site  uses  a  yellow  wagon animated icon to point me at the
>     schedule,  and does not provide a label somewhere saying that this
>     is  for  the  yellow line, thus only relying on my capacity to see
>     the  color,  I  suddenly  cannot understand this site: it does not
>     transform gracefully.
>     If  the  schema designer hasn't provided a way to attach alternate
>     content  to  some  rich  piece  like an animated yellow wagon, the
>     content  provider will not reach all of his/her audience with this
>     information.
>     Suppose  now  in  a  different  page this Web site provides a nice
>     clickable  2D map with all the stops and ask me to select my start
>     and destination. If a simple list of the line stops is provided in
>     textual  form, it does transform gracefully: it's not as fast as a
>     couple  of  mouse  clicks,  so  there is some "degradation" in the
>     system, but a user reliant on text can obtain the information.
>   * Another  aspect  of  "understanding"  is  that in order for a User
>     Agent  to  make  sense  and gracefully transform the content of an
>     arbitrary   schema-based   document  some  semantics  have  to  be
>     disclosed.    By    reusing    or   binding   a   priori   unknown
>     elements/attributes  to well know ones (in XML core or HTML), this
>     is achievable.

IJ: Please refer to the definition of "recognize" in UAAG 1.0,
rather than use the term "understand".
 
> Appendix C: Acknowledgments

> In  addition  to  the editors, the following WAI Protocols and Formats
> Working  Group  (PF)  participants  have  contributed  directly to the
> content of this document:
> 
> Kynn  Bartlett  ,  Geoff  Freed, Al Gilman, Vijay Gummadi, Ian Jacobs,
> Chris  Lilley,  William  Loughborough,  Charles  McCathieNevile,  Dave
> Pawson, Gregory J. Rosmaita, Aaron Swartz and Carlos A. Velasco.
> 
> Appendix D: References

IJ: Please add references to the other Guidelines documents and
please mark up references in a style consistent with other W3C
technical reports (e.g., check out how UAAG 1.0 references are marked
up).
 
>   * W3C WAI Home page
>   * WAI PF Home page
>   * W3C XML Home Page

-- 
Ian Jacobs (ij@w3.org)   http://www.w3.org/People/Jacobs
Tel:                     +1 718 260-9447
Received on Tuesday, 25 September 2001 19:21:16 GMT

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