Re: notes on conference call of 15 July

Bruce, on response to the notes of 15 July:

>> >Ron asked about the possibility of using the display list format as an
>> >entry point for those who would like to transmit only visual data.
>> >The idea would be to filter from TeX or the current ISO 12083 Math DTD
>> >data to display list format directly, rather than trying to "upgrade"
>> >legacy data or machine-ambiguous data to HTML-Math form.  Neil felt
>> >that our display list specification already carried much of the
>> >information which the expression tree carries, and that there is
>> >nearly a one-one correspondence between the two trees.  Whether this
>> >is actually true or whether is should be true seem to be questions in
>> >the air at the moment.  [Bruce, what was your intent?]
>> 
>> Can you clarify the suggestion? I'm not completely sure what is being asked.

Perhaps vaguely, I have the idea that layout schemata such as
mfraction, mroot, mscripts, munderscript, moverscript, mprescripts,
etc.  correspond to ISO 12083 elements fraction, radical, sup, inf,
top, bottom, etc. (the correspondence isn't quite parallel as given
here).  Generally, my understanding of the layout schemata is that
they are our abstract handle on visual layout:

   Every expression in HTML-Math ultimately specifies the relative
   sizes and arrangement of a collection of symbols layed out in a
   "logically 2-dimensional" manner. This structure is specified not
   as coordinates, but in terms of a small set of "perceptual
   primitives" or "layout schemas" which are sufficient to describe
   almost all of the commonly used notations in existing typeset
   mathematics. This choice of level of representation is both as
   general and as abstract as possible while still being based on
   the structure of the notation for an expression, rather than
   purely on its semantic structure or meaning.

						- Wolfram proposal

The "logical 2-dimensional layout" is also what ISO 12083 (the current
version, not the update being generated now) addressed.  These weren't
the words used by the standard, but I think that was the spirit.  So
my question is whether the structure of the ISO standard and our
method of logical 2-dimensional layout can be aligned so as to make it
possible for people to filter directly (and without hand-standing) to
the display list format and to avoid the expression-tree (which
resides at a logically higher level in my view, although Neil was
reluctant to agree to this).  I'm just thinking that this creates a
smooth connection between our work and the world of 2-D layout.
Upgrade to expression-level wouldn't be required, but since we will be
supporting a layout level, we support the work of others if we make
our layout primitives equivalently "universal" as those of 12083.  The
"logical" 2-D layout model is clean insofar as it is well-understood
and "closed" in certain natural ways.

I'm not sure this answers your question, though, Bruce.  Perhaps I'm
still waving my hands too much.  Let me know.

-Ron


I suspect there's a conceptual parallel here also to the layers of
OpenMath, "expression" being a layer above "layout".  Can we give
entry at the layout layer?