equations in HTML

Paul Topping (ptopping@lightside.com)
Mon, 12 Sep 94 12:13 PDT


Message-Id: <m0qkGot-000FVHC@covina.lightside.com>
Date: Mon, 12 Sep 94 12:13 PDT
To: www-html@www0.cern.ch
From: ptopping@lightside.com (Paul Topping)
Subject: equations in HTML

Hello,

In what I think is the latest HTML 2.0 specification, support for math has
evidently been dropped due to lack of consensus on how math should be
represented. Instead, HTML creators will have to use an Image Element. This
will be some kind of bitmap. Unfortunately, the <img...> tag does not give
sufficient alignment control to adequately do the job.
 
Equations, especially those that are likely to be placed in-line (as
opposed to those in their own paragraph), have a natural baseline. For
example,
                        ___________
                       |     b - c |
   Here is an equation:|a + -------|.
                       |       2   |
                       |___________|

In this equation, the baseline of "a" should align with the surrounding
text. Unfortunately, the <img...> tag allows only top, middle, or bottom
alignment. What is needed is to be able to specify a distance from the
bottom edge of the image to the internal baseline.

I believe the utility of this kind of alignment is not limited to math,
chemical equations have similar requirements. In fact, any text-based
notation will generally benefit from such an alignment feature.

We at Design Science have some experience with this. We market MathType, a
point-and-click mathematical equation editor that currently runs on the
Macintosh and under MS Windows. On both platforms, MathType embeds baseline
position information in equations written using the os's native picture
format so that importing applications can handle baseline adjustment
automatically. Many document-centric applications on both platforms DO
handle this just fine (e.g. Aldus PageMaker, Microsoft Word, ...).

I think what I'm proposing would involve adding an alignment attribute to
the IMG construct that would specify an offset (in some suitable distance
units) from the bottom of the image to the baseline within the image. I
know that adding distance values to HTML is generally to be avoided
(express structure, not specific formatting). However, this baseline offset
is really part of the image data itself. As images will normally contain
dimensions (pixels-per-inch, default height and width, etc.), this would
not be out of line.

By the way, we at Design Science are very much interested in the use of our
product in a World Wide Web and/or HTML environment, both for equations
stored as images and those stored in some future HTML markup, should such a
thing ever become a reality. If anybody out there has tried this or is
interested in discussing this, let me know.

Paul R. Topping
Design Science, Inc.
internet: ptopping@lightside.com
voice: 310-433-0685
fax: 310-433-6969