The HyperTeX project
Arthur Smith

(edited by Sebastian Rahtz)

INTRODUCTION

The past year has seen a revolution in the processes of Internet-based
information navigation and retrieval with the advent of easy-to-use
graphical browsers (in particular Mosaic) based on the World-Wide-Web
(WWW). The revolution is a result of two components. First, the
browsers allow a near-uniform (point-and-click or other method) access
to documents in almost any format and from almost any Internet-based
source; along with this the Universal Resource Locator (URL) mechanism
provides a surprisingly easy and uniform way to specify the location
of any document on the net. Second, for certain classes of documents
(html files, or gopher text files) embedded URL's or other addresses
are understood to refer to other, external, documents which can be
followed according to the interests of the person viewing the
document, producing an interconnected web of documents.

The goal of the HyperTeX collaboration is to extend this second
privileged class of documents to include documents based on TeX,
the word-processing language of choice for mathematical and scientific
writing, thus fully incorporating TeX documents into the burgeoning
textbf{web} of information on the internet.  The HyperTeX
introductory document is at http://xxx.lanl.gov/hypertex/.

HOW DOES IT WORK?

The underlying element of our implementation of HyperTeX is the use
of a TeX macro that bypasses the TeX interpretation process and
sends a message directly to the dvi interpreter that processes TeX
output, via the special command. The original HyperTeX specification (due
to Paul Ginsparg, Tanmoy Bhattacharya, and me) uses the initial
characters html: to denote HyperTeX elements in an HTML-like
style. After the initial html: string, the specification is identical
to a restricted form of HTML. The five arguments we have added to
the command are:

href: html:<a href = "href_string">
name: html:<a name = "name_string">
end: html:</a>
image: html:<img src = "href_string">
base_name: html:<base href = "href_string">

The href, name and end commands are used to do the basic hypertext
operations of establishing links between sections of documents. The
image command is intended (as with current html viewers) to eventually
place an image of arbitrary graphical format on the page in the
current location. Currently for XHDVI, image brings up an external
viewer with the image, if such a viewer is available. The base_name
command should be used to communicate to the dvi viewer the full (URL)
location of the current document so that files specified by relative
URL's may be retrieved correctly.

The href and name commands must be paired with an end command later in
the TeX file --- the TeX commands between the two ends of a pair form
an anchor in the document. In the case of an href command, the anchor
is to be highlighted in the dvi viewer, and when clicked on will cause
the scene to shift to the destination specified by href_string. The
anchor associated with a name command represents a possible location
to which other hypertext links may refer, either as local references
(of the form texttt{href="#name_string"} with the name_string
identical to the one in the name command) or as part of a URL (of the
form URL#name_string). Here href_string is a valid URL or local
identifier, while name_string could be any string at all: the only
caveat is that `"' characters should be escaped with a backslash (),
and if it looks like a URL name it may cause problems.

Because this html-based naming scheme is somewhat unwieldy, although
very general, Tanmoy Bhattacharya (tanmoy@qcd.lanl.gov) has written
several collections of TeX macros to simplify things.  The packages
are in http://nqcd.lanl.gov/people/tanmoy/hypertex/. An alternative
LaTeXe package is hyperref, by Sebastian Rahtz and Yannis Haralambous,
which is available on CTAN as
pathmacros/latex/contrib/supported/hyperref. This has additional
functionality for conversion to PDF.

HOW DO I USE IT?

There are currently three dvi interpreters that understand the
HyperTeX specials: XHDVI{} for X windows, HyperTeXView.app for
NextStep, and dvihps, a version of dvips that understands HyperTeX
and puts pdfmark commands in the output for Adobe's Distiller to
process.  For a TeX document that has already been processed to a
dvi file with HyperTeX elements, viewing the internal hypertext is
almost trivial --- you just fire up the dvi previewer and
navigate by button clicks.

The software available is:

1. A HyperTeX viewer based on xdvi-18, modified by Arthur Smith.  
ftp://snorri.chem.washington.edu/hypertex/xhdvi_0.6.tar.Z 

2. HyperTeXview.app, courtesy of Dmitri Linde (also the author of
InstantTeX.app) for NextStep, precompiled for Motorola and Intel-based
NeXT machines. See http://xxx.lanl.gov/hypertex/index.html#dvi for
availability.

3. dvihps, from Mark Doyle, converts the HyperTeX commands to a form
which can be processed by Acrobat Distiller. See the HyperTeX WEB home
page for location. Other PostScript interpreters are free to pick up
the pdfm operators as well. For instance, Tanmoy has hacked Ghostview
to pick up the links and make them active.  This can be found at
http://nqcd.lanl.gov/people/tanmoy/hypertex/ghostview-1.5-hacked.tar.gz.

Here is where the power of TeX's macro capabilities appears.
A working internal hypertext document can be made from a LaTeX 
document with a one-line addition to the file, using one of the
hypertex macro packages. These convert the standard LaTeX  markup
into hypertext links between the different sections of the document,
so that references to equations, tables, footnotes, and section
headings are in place, and bibliographic references and figures
refer to the bibliography entry or figure caption.

The macros developed thus far use standard naming conventions
for the underlying structures in LaTeX and other standard
macro packages, so that appending #equation.2.3, #page.7,
#figure.4, #table.2, etc. to the URL for any TeX file processed
with these packages will go to the right place, allowing
easy hypertext reference to the internal structure of other
documents.

HOW DO I STAY IN CONTACT?

The Hypertex discussion group is
a mailing list based at FTPsnorri.chem.washington.edu which I
maintain. Send me e-mail (asmith@mammoth.chem.washington.edu)
if you want to join the list, or send queries directly to the mailing
list: hypertex@snorri.chem.washington.edu.