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RE: BIG ISSUE -- re Delivery Units

From: Bailey, Bruce <Bruce.Bailey@ed.gov>
Date: Thu, 9 Feb 2006 14:04:00 -0500
Message-ID: <CCDBDCBFA650F74AA88830D4BACDBAB50B2D4B97@wdcrobe2m02.ed.gov>
To: <w3c-wai-gl@w3.org>

I am responding to a few threads in this single message.

Clearly I am not quite parsing the difference between Web Unit and Perceivable Unit.  Could a Perceivable Unit (e.g., typical frame based web site) contain multiple Web Units?  Is a strict hierarchy applicable? 

Content >= Perceivable Unit >= Web Unit >= Delivery Unit

> That works well technically but would an interactive movie  
> be viewed by many as a [web] document?

That is, I would argue, an easier lesson that teaching what is a "Web Unit".  Document has less paper connotation than page at least, and people have dissociated Web Page from hard copy.

> Putting perceivable unit back in you get [snip]

My point is that the current definition of content needs to be seriously reworked, since just substituting Web Unit for Delivery Unit doesn't work.  You can't include Perceivable Unit in the definition of "content" without defining Delivery Unit.  Will Delivery Unit still appear in the Glossary?

I respectfully suggest that the challenge, and solution to this Big Issue, is to define content without referencing Web Unit.

>> Structure:
>> 1. The way the parts of content are organized in relation to each other and;
>> 2. The way content is organized.

> I like it.  We should consider it.  Looking at it closer, 
> I'm not sure I understand the difference between 1 and 2. 
> Can you explain?  Or suggest better wording for #2 so it is clear?

I just substituted content for Web Unit from your most recent definition for Structure.

A longer definition we are kicking around here (borrows from other sources):
Structure:  Includes the hierarchical arrangement of the content and other relationships between document elements.  Structural elements convey organizational meaning beyond typographical formatting.  Examples of structure include the default order of paragraphs, cross-references, and the correspondence between header and data cells in a table.  Examples of structural elements include headings, lists, footnotes, table of contents, etc. 

> Also - the rule doesn't limit its scope to your scope.
> The way you wrote it, it was to all content.
> Not just content within a claim. 

It is not clear to me that it is sensible to consider content that is beyond the scope of a conformance claim.  My shop test web sites and software against the 508 Standards multiple times a week and the issue of what it is that we are evaluating never comes up.  Along that line, what it is exactly we are passing or failing is also not ambiguous.

> Hmmmm example. 
> The stop sign is used in one location to indicate the 
> control for marking something as not done.  In another 
> it is used to mark things that are forbidden or don't work.
> A site may have a hundreds of thousands of pages and 
> thousands of authors.  Requiring that they all do things 
> exactly the same is not realistic or possible. 

Good example, but not one that would be likely to be a problem.  There may be multiple stop sign images, used in a variety of ways, but even ones that are nearly visually identical almost certainly point to different file / directory path names.  If the large sight is tightly controlled, exactly the same image *could* be used perfectly consistently.  If the site is looser, then there are probably multiple claims for WCAG 2.0, and therefore multiple instances of scoping the applicable content.

Tying these recent threads together, here's a quick cut at the SC that currently use Delivery Unit.  They are re-written here so as to avoid Web Unit as well.  Only 2.4.4 was a stretch.

2.2.2:  Content does not blink for more than 3 seconds, or a method is available to stop any blinking.

2.4.2:  More than one way is available to locate content where not the result of, or a step in, a process or task.

2.4.3:  Repeated blocks of content are implemented so that they can be bypassed.

2.4.4:  Content has titles wherever applicable to the baseline technology.

2.4.5:  Each programmatic reference to other content is associated with text describing the destination.

2.4.7:  When content is navigated sequentially, elements receive focus in an order that follows relationships and sequences.

2.4.8:  Information about the user's location within content is available.

3.1.1:  The primary natural language or languages of content can be programmatically determined.

3.2.3:  Navigational mechanisms that are repeated occur in the same relative order each time they are repeated unless a change is initiated by the user. 

3.2.4:  Components that have the same functionality are identified consistently. 

4.1.1:  Content can be parsed unambiguously and the relationships in the resulting data structure are also unambiguous.
Received on Thursday, 9 February 2006 19:04:12 GMT

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