from
The Free On-line Dictionary of Computing (8 July 2008)
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)