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Re: Revision to the definition of 'Element'

From: Al Gilman <asgilman@iamdigex.net>
Date: Fri, 20 Oct 2000 20:36:11 -0400
Message-Id: <Version.32.20001020193541.041b0f00@pop.iamdigex.net>
To: "UA List (E-mail)" <w3c-wai-ua@w3.org>
1.  Why is this conversation happening now?  Are we making changes like
this to
the PR draft?

2.  There is no need for a Term of Art, here, because the sense of
'element' in
the WCAG provisions that are the basis for the UAAG provisions in question
is a
natural English sense of "a constituent part" [c.f.
<<http://www.m-w.com/cgi-bin/dictionary>http://www.m-w.com/cgi-bin/dictionar
y>,
search on 'element,' select sense #2].  That said,  Let me clear up the usage
in this area just a bit.

There is rampant in the community an ambiguity in the use of 'element' between
denoting an actual part of an actual document [instance] vs. an element type
specified (in a DTD or otherwise) for use in markup to delimit and classify
the
previous, more concrete sort of 'element.'  To make the distinction clear, one
could use 'element' and 'element type' but often 'element' gets reassigned and
we wind up talking about 'element instance' and 'element.'  Under the
circustances there is no reader-safe usage except to say 'element instance'
when one means a specific part of a specific document, and 'element type' when
one specifically means a category of the above, such as for example all the
element types defined in HTML, the dialect of SGML.

However: the sense of 'element' in the WCAG 1.0 discussion of "text
equivalents
for non-text elements" is the natural English sense of "a constituent part"
and
not the syntax-technical sense of "an instance of a markup construct
defined as
an element in the formal specification of the markup dialect."  The fact that
it is not the technical sense may bear mentioning, but this is a warning,
not a
'definition.'

Note:  The phrase 'logical construct' is much too broad as it includes
categories such as 'connective' or 'preposition' or 'reference' which are
never
referred to as 'elements' in the disucssions in the WAI documents.  The
category of 'logical constructs' that we use 'element' for is 'element
types.' 
There is no need to fall back any further into looser categories.

Warning 1: It is important to understand the design elements of a web page as
including the actual image embedded in the document by an IMG element in the
markup language, although regarding the document as just the HTML text of the
source one would find that only a reference to the image is preseant in the
IMG
element in the HTML file.

Warning 2: It is perfectly legitimate, however, for someone to talk about
header font and type color scheme as elements of a company's branding scheme. 
This is a pattern of properties that is not a document part and it is not
represented by an XML or SGML element type definition in the  formal
organization of the markup language.  But it can be said in one of our
documents without breaking our usage because it is just another example of the
plain English sense of 'element.'  The key is that it is made clear in the
context what this syndrome of presentation properties is an element (i.e. part
of component) _of_.

There was question as to whether 'element' refers to a type of content.  Not
quite.  The point is that all the named elements in HTML and other SGML and
XML
applications _do_ have connotations as to categories that the content range so
marked falls within.  But these categories are often heuristic, that is to say
not machine-interpretable without the aid of a natural-language-capable
human. 
So although one of the common senses of 'element' is 'element type,' and
'element type' does contain information about what kind of stuff is in there,
an 'element type' is not a kind of stuff, but rather a kind of part which has
restrictions as to the kind of stuff one will find in it (and its role in the
context).

Webster lists "a constituent part" as the second sense of 'element' and
that is
the generic sense used throughout UAAG and the rest of the WAI literature.  It
is inadvisable to try to give a reserved meaning to 'element' in the UAAG as a
whole.  If you want to make the usage more precise in various places, it could
be useful to introduce glossary entries for "element instance" and "element
type" and place a note in the glossary indicating that 'element' has been used
for either of these or the Webster sense "a constituent part" interchangeable
where it is clear from the context which of these is intended.  We should
endeavor, and say we have so tried, to use "element instance" or respectively
"element type" where the distinction is important.

Note: there is no need to be concerned about how 'element' is defined as used
in the glossary entry for "text element."  The introduction of "text element"
in the glossary is gratuitous.  Searching for this phrase encounters no hits
until it appears in the glossary.  It is a self-requiring exercise in
unnecessary definition of terms.  However, if you wish to understand what
"text
element" and "non-text element" should mean in the satisfaction of WCAG,
please
consider the following nominations:

* A _text element_ is a constituent part of the document (i.e. in the general,
not syntax-technical sense) whose content is entirely composed of text and
properties of that text.

* A _non-text element_ is a constituent part of the document (same proviso)
that is not a text element and cannot be reasonably decomposed into
constituent
parts some of which are text elements and some are not.

The main reason for putting a glossary entry in the document is that
readers of
the content may be markup-language-literate and will need to be warned that
the
syntax-technical sense is not what is intended [in the WCAG language].  Note
that since the issue here is echoing the WCAG requirement, the appropriate way
to get usage clarification would be to ask the WCA WG for an interpretation of
the document.

All of this is dependent of understanding that 'part' in the above indicates
something which contains a subset of the content of the document, _and_ would
be recognizable by a reasonable user as a thing in its own right.

Al

At 05:15 PM 2000-10-20 -0400, Hansen, Eric wrote:
>I wanted to make sure that our definition of "Element" adequately covers our
>usage in definitions such as "Text element". Is our usage as a "logical
>construct" or something else? I think it as a "unit of content" rather than
>necessarily being tied to particular "type of content". For example, a
>"multimedia presentation" might be considered an element, but also might its
>visual track or even a text equivalent of a visual track might be considered
>"elements".  
>
>Your comments welcome.
>
>Old (29 September 2000):
>
>"Element This document uses the term "element" both in the XML sense (an
>element is a syntactic construct as described in the XML 1.0 specification
>[XML], section 3) and more generally to mean a type of content (such as
>video or sound) or a logical construct (such as a header or list)."
>
>New:
>
>"Element This document uses the term "element" both in the XML sense (an
>element is a syntactic construct as described in the XML 1.0 specification
>[XML], section 3) and more generally to mean a unit of content (text element
>or non-text element) or a logical construct (such as a header or list)."
>
><END OF MEMO>
>  
Received on Friday, 20 October 2000 20:10:47 GMT

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