[W/K] :: abstract syntax

  abstract syntax
       
           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)