Rendering Rules and Styles

We begin this chapter by building up a general framework of rendering rules and styles in Section 4.1. Rendering rules enable the generation of different audio views of the same object. Section 4.2 introduces the concept of fleeting and persistent sound cues and uses these to develop an audio layout for conveying structure present in typical document content, e.g., sections and itemized lists.

We then develop a system of audio notation to convey mathematical content and present a collection of rendering rules for producing such audio notation in Section 4.3. The processing required to produce context sensitive renderings from the quasi-prefix representation (see Chapter 2.2) is covered in Section 4.4. Some descriptive rendering rules for mathematical content are discussed in Section 4.5.

When reading complex mathematics in print, we often use a chunking strategy: rather than read the entire expression, we first obtain a high-level view by grouping related subexpressions. This becomes even more necessary in oral communication —otherwise, the listener has to remember the mathematical content. Complicated mathematical expressions can be better communicated by first substituting names for complex subexpressions to provide a quick overview. This process, called rendering with variable substitution, is described in Section 4.6. A flexible mechanism for delaying the rendering of specific objects is described in Section 4.7. Appendix A.4 documents the external interface to the system of rendering rules and styles.

Throughout this chapter, we describe how AS TE R renders different object types. Note, however, that the user is free to customize all of the renderings produced by AS TE R.

4.1 Rendering Rules and Styles

Rendering Styles

4.2 Rendering Document Content

Rendering Hierarchical Document Objects

4.3 Rendering Mathematics

Producing Audio Notation for Mathematics

4.4 Processing the Quasi-Prefix Form

Recognizing Special Patterns

4.5 Descriptive Renderings

Rendering Integrals

Obtaining Different Views

4.6 Variable Substitution

Examples

Criterion for Applying Variable Substitution

Motivation for above Criteria

Basic Algorithm

Refining the Algorithm

Substitution Threshold Values

Naming the Substitution

Additional Examples

Implementation Issues

4.7 Floating Objects

Example of a Floating Rendering Rule

Using Floating Renderings