Feature Set Matching Sample Code
================================

NOTES:

Class 'FeatureSet' provides the main entry points for this code.
Namely: Parse, Format, Write, Match, Simplify.

Class 'Test' is a runnable test harness that also provides example
use of the feature set parsing and matching code.  File 'Test.out is
a copy of the output from this test harness.

Classes of the form xxxPredicate are used to represent different
types of feature set predicate, and also contain code for simplifying
predicate expressions.  These correspond roughly to the syntax elements
declared in RFC 2533.

The values TRUE and FALSE are represented by the special auxiliary
predicates (TRUE) and (FALSE).


TODO:
(a) Add support for q-values -- and other parameters.
(b) Add support for unit designators
(c) Add support for auxiliary predicate parameters.
(d) [MAYBE] Revise algorithm to keep set expressions intact,
    and use additional rules to handle them.  This should
    help contain the explosion of conjunctions when
    converting to DNF.


Version 1.00A   27-Apr-1999
---------------------------

Initial working version, based closely on RFC 2533.


Version 1.00B   27-Apr-1999
---------------------------

Test handling of (TRUE), (FALSE) in conjunction.

Test handling of (TRUE), (FALSE) in disjunction.

Test handling of various set expression forms.

Fix rational number parsing bug

Fix set expression [3..2] simplification bug

Fix rational comparison bug.

Added support for basic auxiliary predicates.  Redefined
TRUEPredicate and FALSEPredicate as instances of AuxPredicate.
(At this time, there is no support for auxiliary predicate
simplification).


Version 1.00C   29-Apr-1999
---------------------------

Implemented multiline expression formatting.

Add examples from RFC 2531 into test data set.

Revised multiline output to place as many complete
predicates on a line as will fit.


Version 1.00D   18-May-1999
---------------------------

(Revise algorithm to produce more intuitive results
based on <=, >=, = and != operators.)

Add EQFIRST processing tag value to Predicate.

Add logic to ANDPredicate to process EQFIRST tag value.

Change AtomicPredicate simplification to use EQ, NE, GE and LE for
its four primitive comparison operators.

ANDPredicate.ReducePredicates re-worked to perform reductions based
on EQ, NE, GE, LE.


Version 1.00E   14-Jun-1999
---------------------------

Add copyright notice, redistribution terms and conditions and warranty
disclaimer to each source module.

Change algorithm description references to indicate
<draft-klyne-conneg-feature-match-xx.txt> rather than RFC 2533.


Version 1.10A   06-Apr-2000
---------------------------
Updated by Graham Klyne, Content Technologies Ltd., to include calculation of
feature set hash value per <draft-ietf-conneg-feature-hash-xx.txt>


Version 1.20A   05-Mar-2002
---------------------------
Updated by Graham Klyne, Nine by Nine.
Revised the pretty-print formatting logic around modules Formatter and FormatterBase.  Added Auxilliary predicate definition and substitution (without support for parameters).  Added test program for IPP-fax examples.