Working Draft 10-Jul-1997

6. Entities, Characters and Fonts

6.1 Introduction

6.1.1 The Intent of Entity Names

Notation has proved very important for mathematics. Mathematics has grown in part because of the succinctness and suggestiveness of its evolving notation. There have been many new signs evolved for use in mathematical notation, and mathematicians have not held back from making use of many symbols originally developed elsewhere. The result is that mathematics makes use of a very large collection of symbols. It is difficult to write mathematics fluently if these characters are not available for use in coding. It is difficult to read mathematics if glyphs are not available for presentation on specific display devices.

This situation poses a problem for the HTML-Math Working Group. It does not fall naturally within the purview of a math for HTML specification and DTD production to worry about more than the entities allowed in the DTD. However, as experience has shown, a long list of entities with no means to display them is of little use, and a cause of frequent frustrations in trying use a standard. On the other hand, a large collection of glyphs or characters without a standard way to refer to them is not of much use either.

The HTML-Math Working Group has therefore taken on directly specification of part of the full mechanism of proceeding from notation to final presentation, and is collaborating with organizations undertaking specification of the rest.

For instance, we try to use entity names that are contained in ISO TR 9573, which supersedes the ISO TR 8879 annex as far as math is concerned. There are considerations of mathematical usage that do on occasion militate against this, and the TR 9573 lists need supplementing. We hope to be able to agree with the TR 9573 WG on suitable extensions, in the course of the revision of their document that they are presently undertaking.

In addition, a subcommittee has been preparing a comparative listing of math symbols and the names used for them in the ISO, TeX and Mathematica worlds. Tables showing the results are accessible from this section. This work is also shared with the STIX project of the STIPUB group of scientific and technical publishers.

For the above reasons, the work of the Working Group on entities, characters, glyphs and fonts is not expected to be completed, even in its first phase, until July 1997. The tables below are a good indication of the form intended, and the information in the comparative database is supposed to be correct, but this Chapter 6 is probably further from the final version of the Working Group's recommendation in September 1997, than the draft versions of other Chapters.

6.1.2 The STIX Project

The STIX project team leader, Nico Poppelier, is a member of the HTML-Math Working Group. The STIX project, set up by the STIPUB group of publishers, aims to formulate a collection of characters needed in the course of scientific and technical publishing. A database, which is an extension of the comparative listing referred to above, is being produced by collaborating publishing organizations. Then the team will propose to the Unicode consortium the additions to the next revision of the Unicode character set that this process shows are needed , together with the appropriate character codes. Finally the STIX project will commission the production of a complete set of fonts covering those Unicode characters for science and technology, to be made available to the public under license but free of charge. The STIPUB group recognizes that easy availability of the characters and fonts greatly facilitates communication.

6.1.3 Entity Listings

This chapter of the MathML proposal contains a listing of entities for use in MathML. This is given in tabular form, showing the name proposed, the present Unicode corresponding, and an example of a corresponding glyph when available. The headings are

MathML entity	Unicode	Sample glyph

The names are, as remarked above, with some exceptions those in use in TR 9573; there are additions of alternatives too if that makes sense for mathematics. Since this is a first draft proposal for comment, it is to be expected that some entity names will be revised later.

There are cases where a glyph image is not yet available, and the tables will be completed in later editions. Since the GIF images are from more than one source the quality and the form of the background vary.

The ordering of the tables is essentially by Unicodes at the present time. They are divided into groups of 100 to make them easier to load into a browser since they involve about one GIF image per character. Later we expect to offer other groupings of this collection of entities. In the Unicode column, if there is no Unicode available then the AFII number appears in brackets, like [2139], or if that is also unavailable then a code from an internal grid system appears in double brackets, like [[cbx]]. For instance:

MathML entity	Unicode	Sample glyph
&andand;	[DB3D]
∈	[[bob]]

Entity tables

To provide more background on the characters used by mathematics we provide also the larger tabular comparative database showing codes and meanings in other common math environments. The HTML-Math Working Group is very grateful to Elsevier Science and to Wolfram Research (makers of Mathematica ®) for making available so much useful data to us. These tables have 15 columns.