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Subject: Re: [docbook-tc] adding CALS attrs to HTML tables
Hi Paul,
As you say, examining the purity of CALS tables in DocBook is useful. The
CALS table model supports two parameter entities %bodyatts; and %secur; for
attributes, which don't seem to be defined in the CALS standard. [1] I take
this to mean that any number of additional attributes can be defined in
those PEs to add to CALS tables. In DocBook, the bodyatts PE is populated
with floatstyle, label, and the new rowheader. The secur PE is populated
with all the DocBook common attributes, of which there are 17 in V5.0. So
CALS interoperability seems to permit the addition of any number of
attributes on the table element through these two extension parameters.
The HTML table model does not have such an extension mechanism. In the
current proposal for HTML tables in V5.0 [2], the common attributes are not
permitted on the HTML table element or its HTML descendents. I have to
wonder if that was intentional, or if this concept of table model purity
requires it. I suspect DocBook users would revolt if they didn't have the
common attribs on HTML tables. So perhaps we should also discuss whether
HTML table elements should permit the DocBook common attribs. If those are
permitted, then adding a couple more attribs from the CALS table model seems
OK.
Regarding interoperability of table models, currently an XML application
supporting a CALS table has to support, or at least recognize, the
additional attributes defined in the bodyatts and secur parameter entities.
For example, an editing application needs to read the schema and add those
attributes to the choice list for CALS tables. Those attributes don't
affect the element content models, so the application can properly arrange
the rows and columns on the screen.
If an application also supports HTML table markup in DocBook, they will also
have to read the schema, because the table cells contain content that is not
necessarily HTML. If it handles the CALS tables with arbitrary attributes,
it would seem adding attributes to HTML tables would not create problems.
Again, the extra attributes would not modify the content models of the HTML
table elements.
If interoperability means moving an HTML table between a DocBook document
and an HTML file, then a few extra attributes in the HTML table would not be
a problem. HTML browsers simply ignore extra attributes. A bigger problem
would be any DocBook markup in the table cells, which could create
unreadable output. In a sense, we have already created a hybrid table model
by permitting DocBook markup within an HTML table cell. So I think it would
be useful for those who desire interoperability to define it in terms of
real requirements.
So let's first decide if HTML tables should have the common attribs.
[1] http://www.oasis-open.org/specs/a502.htm
[2] http://www.docbook.org/tdg5/en/html/html.table.html
Bob Stayton
Sagehill Enterprises
DocBook Consulting
bobs@sagehill.net