minutes of teleconference, 16 sep

Notes on HTML-Math Interest Group Teleconference Call
16 Sep 96
---------------------------------------------------------------------

In attendance:

Ste'phane Dalmas Safir, INRIA
Patrick Ion      Mathematical Reviews
Robert Miner     The Geometry Center
Bruce Smith      Wolfram Research, Inc.
Neil Soiffer     Wolfram Research, Inc.
Bob Sutor        IBM
Stephen Watt     Safir, INRIA
Ron Whitney      American Mathematical Society
Ralph Youngen    American Mathematical Society

[Notes prepared by RW.  Corrections welcome.]
---------------------------------------------------------------------

The discussion centered on operator precedence parsing (OPP) as the
parsing method of choice in the Wolfram Proposal.  For this
discussion, OPP is contrasted with a "function application" (FA)
approach which uses prefix-operators in place of infix- or
postfix-operators.

Bruce said that when he joined the committee, Dave had been a strong
proponent of OPP, perhaps because it allows commonly-understood and
easily-entered notation for simple math.  Bruce's first inclination
might have been to use more of an FA approach, but Dave had made a
convert of him.  Stephen suggested that this might make extensibility
more awkward (allowing someone to define an operator with the
precedence of addition on the left, but of times on the right), and
Bruce said that, although he felt considerations about extensibility
are very important issues, they should not necessarily drive the basic
approach.

Ron said that he had been attracted to OPP because he felt that
translation from layout languages without semantical constructs to an
OPP language might have fewer obstructions (the intuition being that,
since the OPP of the Wolfram Proposal is based on the general
precedences of visually oriented layout, a filter from TeX to
html-math could more easily hit the visual target and disregard the
semantically oriented information which might be necessary for a
"proper" html-math encoding).  This point of view was not supported by
others, although Neil did argue at one point that there was some
greater chance for a linearization which targets the Wolfram OPP table
to "look ok" (i.e. be visually acceptable, albeit perhaps not
entirely semantically so).

Stephen [[and others, I think -RW]] expressed concern about a standard
that is only a slight perturbation of TeX, feeling that this will
mostly cause confusion to those who try to directly edit both
html-math and TeX notation.  Could our basic notation be TeX?  Bruce
said he felt the Wolfram Proposal does capture "expression structure",
which TeX does not, and is crucial to proper semantical handling.
Stephen suggested that we might use a few of the central TeX
operations, but switch to an FA approach otherwise.  He was concerned
that people (authors and editors) would have to learn a host of
operator precedences which would make the system awkward to use.
Bruce and Neil said they felt that users would become familiar with
the needs of notations they use regularly, and would group expressions
explicitly otherwise.

Stephen was concerned about imprecisions which remain in the OPP of
the Wolfram Proposal, and asked whether a formal grammar existed.
(There are about 90 different precedences at this point.)  Bruce and
Neil said they felt one could be written down, although handling
embellishments on operators complicates matters, and their work for
Wolfram had actually exceeded a certain internal, hard-coded parameter
for a public domain YACC.  This is not a limitation in concept,
however.

The discussion ended with Ron asking Stephen to provide some more
concrete examples of what might be problematic WP-style encodings
(i.e. encodings in the Wolfram Proposal for html-math which might be
ambiguous to readers or might hit the wrong target when rendered to a
CAS).



[[ As with other minutes of teleconferences, these minutes do not
claim to summarize all conversation, although conversational topics
are not knowingly omitted.  It is difficult to summarize these
discussions.  I welcome additional remarks about the conference, and
suggest that individuals submit more detailed statements about their
opinions on specific topics.  -RW]]