Handling of unknown attributes of a tag by a browser

fwilliam@ccs.carleton.ca (Fred Williams)
From: fwilliam@ccs.carleton.ca (Fred Williams)
Message-id: <9307270157.AA24520@superior.YP.nobel>
Subject: Handling of unknown attributes of a tag by a browser
To: www-talk@nxoc01.cern.ch
Date: Mon, 26 Jul 93 21:57:12 EDT
X-Mailer: ELM [version 2.3 PL11]
Status: RO
A question concerning the handling of unknown attributes of a tag
within HTML or HTML+ proposal.  

I am currently defining the representation of building standards in
computerized form for my masters thesis.  I intend to use HTML+ as the basic
markup tool for this representation.  However it does require the
ability to assoicate an attribute or attributes to figures, headers
and paragraphs which will be used by both 'extended' browsers and the

However I would like the information to be available to other browsers
which would support HTML+ but not the specific extensions.  Through
the RFCs that are available for HTML and HTML+ I cannot locate a
definite answer on how a browser is to handle an undefined attribute.
Is it intended to:
          1)        just ignore the illegal attribute and process the
                    tag otherwise,
          2)        or, ignore the tag and associated text to the end
          3)        or some variation on the above.

For example, in HTML+, the following tag <p classifier="XXX"> I would
think should still generate a paragraph break even if the attribute
'classifier' is not understood by the browser.  The same would be for
<h2 classifier="YYY">

Thanks in Advance

Fred Williams 
School of Engineering
Carleton University
Ottawa, Ontario