Hypertext specials

Current support for the World Wide Web in the TeX system does not involve modifying TeX itself. We need only define some specials; Arthur Smith (@email{apsmith@aps.org}), Tanmoy Bhattacharya, and Paul Ginsparg originally proposed and implemented the following:

html:<a href="xurl">
html:<a name="name">
html:</a>
html:<img src="xurl">
html:<base href="xurl">

Like all TeX \special's, these produce no visible output, and are uninterpreted by TeX itself. They are instructions to DVI processors only.

Here, xurl is a standard WWW uniform resource locator (URL), possibly extended with a `#type.string' construct, where type is `page', `section', `equation', `reference' (for bibliographic references), `figure', `table', etc. For example,

\special{html:<a href="http://www.maths.tcd.ie/~tim/ch1.dvi#equation.1.1">}

is a link to equation (1.1) in an example document by Tim Murphy.

See @url{http://www.w3.org/hypertext/WWW/Addressing/Addressing.html} for a precise description of base URL's. (That itself is a URL, in case you were wondering.)

Descriptions of the \special's:

`href'

Creates links in your TeX document. For example:

\special{html:<a href="http://www.tug.org/">}\TeX\ Users
Group\special{html:</a>}

The user will be able to click on the text `TeX Users Group' while running Xdvi and get to the TUG home page. (By the way, this is for illustration. In practice, you most likely want to use macros to insert the \special commands; reference above.)

`name'

Defines URL targets in your TeX documents, so links can be resolved. For example:

\special{html:<a name="#paradise">}Paradise\special{html:</a>}
is exactly where you are right now.

This will resolve an `href="paradise"'.

`img'

Links to an arbitrary external file. Interactively, a viewer is spawned to read the file according to the file extension and your `mailcap' file (see the Xdvi documentation).

`base'

Defines a base URL that is prepended to all the name targets. Typically unnecessary, as the name of the DVI file being read is used by default.

The `img' and `base' tags are not yet implemented in Dvips or the NeXTSTEP DVI viewer.