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AsTeR chooses identifier names that convey some information about the object being replaced. This has two advantages:

- An identifier like ``summand'' when referring to the expression appearing as the summand in a summation conveys more information than the identifier [tex2html_wrap5866].
- When substitutions are spoken after rendering the top-level expression, the listener finds it easier to relate them to the top-level expression.

- Type information. The objects returned by the recognizer
are all typed. So at the very least, we have type information
for all objects,
*e.g.,*mathematical function, parenthesized expression, etc. - Contextual information. The first child of a fraction is called its ``numerator''. The left-hand side of an implication is called the ``premise'' and its right-hand side the ``conclusion''. We have built in this information for standard mathematical objects and provided a flexible mechanism for the user to add or modify such information.
- Special patterns: The special patterns presented in s:special_patterns are also used in synthesizing meaningful names for the substitutions.

Thus, when substituting for the subscript to a summation operator, AsTeR uses the name ``lower constraint''. Since more than one such ``lower constraint'' may be substituted in a general expression, such names are appended with an integer to make them unique. This is how the rendering shown earlier for Faa De Bruno's formula is produced.

TV Raman

Thu Mar 9 20:10:41 EST 1995