Proposed Feature #22

[Seth Proctor <Seth.Proctor@Sun.COM>]

Attached is the description for proposed 2.0 feature #22
(time-in-range). The function is being proposed as an errata item since
it represents functionality that the 1.0 specification was supposed to
contain, but does not.


seth

22: time-in-range function

  Provide a function for comparing that a time of day is between two
  other times of day.

MOTIVATING USE-CASE AND REQUIREMENT

  The XACML 1.0 specification includes a standard representation of time
  in the http://www.w3.org/2001/XMLSchema#time datatype, and also
  includes functions for operating on time values. Some of these
  functions are comparators. One of the motivating uses for these
  comparison functions was to be able to determine whether some time
  falls between two other times (eg, is the access time between
  09:00:00 and 17:00:00). This is a very common access pattern that is
  needed by many.

  Unfortunately, due to the way that time is represented, the comparison
  functions don't actually provide this functionality with any
  guarantees. This was discussed in a thread starting with

    http://lists.oasis-open.org/archives/xacml/200307/msg00044.html

  Therefore, there is no standard way to see if a given time falls in a
  given range of time. The proposed function provides that
  functionality. Because this is a widely needed feature, it's important
  to have a standard way to support this range comparison.

  This feature is being proposed as an errata, since it fixes a problem
  with the specification (namely, there is supposed to be support for
  checking if a time is in a range, but the current specification is in
  error since it doesn't actually support this use case).  

SUMMARY OF OPEN ISSUES

  There is no open issue for this feature, though this change is related
  to open issues associated with the http://www.w3.org/2001/XMLSchema#time
  datatype and its associated functions. These were first raised in

    http://lists.oasis-open.org/archives/xacml/200307/msg00044.html

  These issues were discussed on the list, and there was tentative
  agreement on the given proposal. The issue is currently in front of
  the XMLSchema group.

PROPOSED SOLUTION

  A proposal was already made in

    http://lists.oasis-open.org/archives/xacml/200307/msg00044.html

  for a function named time-in-range that takes 3 parameters (all of
  type http://www.w3.org/2001/XMLSchema#time), and returns true iff the
  first parameter falls between the second and the third parameters. In
  early discussions on the TC list, this solution seems to be
  acceptable.

DETAILED SOLUTION

  This requires no schema changes. Details to follow when a solution has
  been agreed upon.