RFC 2533 (rfc2533) - Page 2 of 37

A Syntax for Describing Media Feature Sets

RFC 2533       A Syntax for Describing Media Feature Sets     March 1999


        3.4.1 Data resource options............................7
        3.4.2 Recipient capabilities...........................7
        3.4.3 Combined options.................................7
     3.5 Feature set predicates ...............................8
        3.5.1 Comparison with directory search filters.........8
     3.6 Describing preferences ...............................9
     3.7 Combining preferences ...............................10
   4. Feature set representation..............................11
     4.1 Textual representation of predicates ................11
     4.2 Interpretation of feature predicate syntax ..........12
        4.2.1 Filter syntax...................................12
        4.2.2 Feature comparison..............................13
        4.2.3 Feature tags....................................13
        4.2.4 Feature values..................................14
          4.2.4.1 Boolean values                              14
          4.2.4.2 Numeric values                              14
          4.2.4.3 Token values                                15
          4.2.4.4 String values                               15
        4.2.5 Notational conveniences.........................15
     4.3 Feature set definition example ......................16
   5. Matching feature sets...................................16
     5.1 Feature set matching strategy .......................18
     5.2 Formulating the goal predicate ......................19
     5.3 Replace set expressions .............................19
     5.4 Move logical negations inwards ......................20
     5.5 Replace comparisons and logical negations ...........20
     5.6 Conversion to canonical form ........................21
     5.7 Grouping of feature predicates ......................22
     5.8 Merge single-feature constraints ....................22
        5.8.1 Rules for simplifying ordered values............23
        5.8.2 Rules for simplifying unordered values..........23
   6. Other features and issues...............................24
     6.1 Named and auxiliary predicates ......................24
        6.1.1 Defining a named predicate......................24
        6.1.2 Invoking named predicates.......................25
        6.1.3 Auxiliary predicates in a filter................25
        6.1.4 Feature matching with named predicates..........25
        6.1.5 Example.........................................26
     6.2 Unit designations ...................................26
     6.3 Unknown feature value data types ....................27
   7. Examples and additional comments........................27
     7.1 Worked example ......................................27
     7.2 A note on feature tag scoping .......................31
   8. Security Considerations.................................34
   9. Acknowledgements........................................34
   10. References.............................................35
   11. Author's Address.......................................36
   Full Copyright Statement...................................37



Klyne                       Standards Track