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Re: [MathML4] Deprecation/Removal of the mfenced element

From: William F Hammond <hammond@csc.albany.edu>
Date: Tue, 26 Jul 2016 14:08:50 -0400
To: www-math@w3.org
Message-ID: <i74m7cp8zx.fsf@hilbert.math.albany.edu>

I have always liked "mfenced".

I think it is useful in catching translations from
well-designed LaTeX profiles.

I think it is useful to preserve as much semantic
information as might be reasonably found, or at least
derived by standard inference, in a well-designed LaTeX
profile.  Toward this end I think it will be good to be able
to continue making a distinction between the two concepts
that might in a computer algebra system be called
"expression sequence", on the one hand, and "list", on the
other.

I have always argued against the strict equivalence.  Less
harm would be done simply by relaxing that lousy standard
than by pulling mfenced.  I have mostly kept quiet my
complaints about processing decisions in the MathML world,
e.g., <mo>, based on CDATA values, in effect, using CDATA as
SDATA.  Really, such practice breaks the paradigm of XML.
In many cases my response to the loss of SDATA is to provide
empty, sometimes defined-empty elements, to replace what
might otherwise have been SDATA.  The gain with this is that
element content may contain markup whereas attribute values
may not.

In that direction another approach would be to deprecate the
"open", "close", and "separators" attributes in favor of new
elements that replace them.  That is, provide an mfenced
head, e.g., <mfhead>, and provide empty-element names for
things allowed as openers, closers, and separators, which are
allowed as children of <mfhead>.  The members of the list
could then be simply the children of <mfenced> that follow
<mfhead>, with the presence of <mfhead>.

I will read more carefully through FW's long list of
processing concerns in a few weeks.

In the end, the design of an XML markup is about the
organization of processing.  This requires time for thought
and experimentation.

                                    -- Bill
Received on Tuesday, 26 July 2016 18:09:15 UTC

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