1.2 What is AS TE R?

AS TE R is a computing system3 for producing audio renderings of electronic documents. The present implementation works with documents written in the TEX family of markup4 languages: TEX, LATEX and AM S-TEX. We were motivated by the need to render technical documents, and much effort was spent on designing audio renderings of complex mathematical formulae. However, AS TE R works equally well on structured documents from non-technical subjects. Finally, the design of AS TE R is not restricted to any single markup language —all that is needed to handle documents written in another markup language is a recognizer for it.

AS TE R recognizes the logical structure of a document embodied in the markup and represents it internally. The internal representation is then rendered in audio by applying a collection of rendering rules written in AFL, our language for audio formatting. Rendering an internalized high-level representation enables AS TE R to produce different views of the information. A user can either listen to an entire document, or browse its internal structure and listen to portions selectively. The rendering and browsing components of AS TE R can also work with high-level representations from sources such as OCR-based document recognition.

This chapter gives an overview of AS TE R, which is implemented in Lisp-CLOS with an Emacs front-end. The recommended way of using it is to run Lisp as a subprocess of Emacs. Throughout this chapter, we assume familiarity with basic Emacs concepts.

Section 1.3 introduces AS TE R by showing how documents can be rendered and browsed. Section 1.4 explains how AS TE R can be extended to render newly defined document structures in (LA)TEX. Section 1.5 gives some examples of changing between different ways of rendering the same information. Section 1.6 presents some advanced techniques that can be used when listening to complex documents such as text-books. AS TE R can render information produced by various sources. We give an example of this by demonstrating how AS TE R can be used to interact with the Emacs calculator, a full-fledged symbolic algebra system.