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Blocks and browser support

From: Michael Cooper <mcooper@cast.org>
Date: Thu, 29 Jun 2000 19:07:47 -0400
To: <w3c-wai-er-ig@w3.org>
Hi - I was asked to pass on Bobby's browser compatibility information. It's
actually available in any local copy of Bobby, but I'm attaching a zip
collection to this message (hss.zip), and the documentation for
understanding them (2 years old) in an html file (hss.html).

I also have a very old action item to propose a technical-ish definition of
"blocks of content" for the purpose of then deciding if a block is "large".
Just for the sake of argument, to throw something out there, I would say:

Most generally, a block is a sequence of similar elements (especially ones
that are defined as block-level elements, such as <p>), delimited by
elements of some other type. So one or more <p> elements in a row is a
contiguous block, ideally delimited on both sides by any heading element, or
the opening/closing body tag.

Other elements define blocks more by virtue of being containers of other
elements. So, and <div> defines a block, as does any list (<ul>, <ol>,
etc.). All the <li> children of a list are members of a block. It gets
trickier when there are nested lists - I would say a nested list both
creates a new sub-block, and is a member of its parent block, but at any
rate does not begin a new block at the same level as its parent.

<div> elements are tricky too because they might include anything. In the
best case, a <div> defines a logical block. In reality, they might encompass
the whole page, or much smaller chunks, down to a single word or character
if they're confused for <span> which I often see. So, I would say that
whether a <div> defines a block depends on the diversity of elements inside
it. If there are a bunch of the same kind of element within a <div>, or
anonymous text (text not even in a <p> element), that <div> defines a block.
But, if there's a bunch of different kinds of elements, especially otherwise
block delimiters such as headings, it may not be useful to think of that
<div> as a block but as a formatting agent. Within it, there would be
several blocks defined by other means. I would say though that a block would
never span across a <div>'s boundaries, so if I had a bunch of <p> tags,
then a closing or opening <div> tag, then more <p> tags, those paragraphs
would be members of different blocks.

Tables also complicates the issue. First, I would say that overall, a data
table is its own block, and a layout table is not (but should be treated as
I do <div> above, as a container element). So, generally, if you had a bunch
of paragraphs, then a data table, then more paragraphs, the data table would
be its own block, and would also delimit the paragraphs before and after it
into distinct blocks. However, I would say this is only true for "large"
data tables. A "small" table might be considered to be a "for example"
within the block of text and not rightfully considered its own block. (The
same would be true of a <blockquote>, by the way). So I have to define
large. That's another discussion, but maybe for now if the table has more
than 20 cells, it's "large".


Michael Cooper
Bobby Project Manager
Technical Designer
CAST, Inc.
39 Cross St.
Peabody, MA  01960
Tel +1 978-531-8555 x265
TTY +1 978-538-3110
Fax +1 978-531-0192
Email mcooper@cast.org

Received on Thursday, 29 June 2000 19:09:58 UTC

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