abstract syntax

language, data A representation of data (typically either a

message passing over a communications link or a program being

compiled) which is independent of machine-oriented structures

and encodings and also of the physical representation of the

data (called "concrete syntax" in the case of compilation or

"transfer syntax" in communications).

A compiler's internal representation of a program will

typically be specified by an abstract syntax in terms of

categories such as "statement", "expression" and "identifier".

This is independent of the source syntax (concrete syntax)

of the language being compiled (though it will often be very

similar). A parse tree is similar to an abstract syntax

tree but it will typically also contain features such as

parentheses which are syntactically significant but which are

implicit in the structure of the abstract syntax tree.

(1998-05-26)