KRSL Plans Working Group - Plans and Activities
DRAFT: 20-Sep-96
The Plan Ontology Construction Group of ARPI is seeking to define a
generic ontology of plans and activitiess. An earlier draft was
arrived at following discussions in late 1994 and early 1995.
The result of this work was the
Draft KRSL-Plans ontology dated 2-Feb-95.
New work, involving a larger group, is now taking place to redefine
this ontology and to seek a larger group consensus on its contents.
The following definitions are the current draft of this ontology.
Level 1: Overall Framework
- A PLAN is a SPECIFICATION of ACTIVITY to meet one or more
OBJECTIVES.
- A SPECIFICATION of ACTIVITY denotes or describes one or more
ACTIVITIES.
- An ACTIVITY may change the STATES-OF-AFFAIRS.
- STATES-OF-AFFAIRS is something that can be evaluated as holding
or not.
- An AGENT can perform ACTIVITIES and/or hold OBJECTIVES.
- An OBJECTIVE may have [one or more] EVALUATION-CRITERIA.
Level 1 Issues Remaining
- a worry about the need for or way in which to include "in the
domain" or "in the model" in the definitions. An earlier
version (2-Feb-95) of the definitions used terms "world" and "model" in a
number of places.
The intention is an interpretation of the world as "the domain in
which activity takes place".
The definitions imply that we ave separation of the domain in which
activities take place and the specification of activities in that
domain.
Issue being considered by Jon Doyle and Mike Uschold.
- a worry that we may wish to have a range of uses states-of-affairs
and that there is no detailed definition for this yet. Current level
1 definition is meant to be uncommitted as to what a states-of-affairs
can relate to. It even excludes the earlier examples we had in order
not to imply any restriction on use (it is simply anything that can be
evaluated as holding or not at the moment). Should level 2 introduce
specific ontolological commitments on this?
Issue being considered by Jon Doyle, James Allen, Mike Uschold, plus
others.
Level 2: The Definition of Activity in the Context of Plans
- An EVALUATION-CRITERIA is an ASPECT of [one or more] STATES-OF-AFFAIRS
or an ASPECT of [one or more] PLANS.
Does ASPECT = FUNCTION?
- An EVALUATION is a predicate (holds/does not hold) or a
preference ranking on [one or more] EVALUATION-CRITERIA.
- An ACTIVITY takes place over a TIME INTERVAL identified by its two
ends, the BEGIN TIME POINT and the END TIME POINT. The BEGIN TIME
POINT is temporally before the END TIME POINT.
- An ACTIVITY-SPECIFICATION may have CONSTRAINTS associated with it
[and its TIME-INTERVAL].
- An ACTIVITY-SPECIFICATION may be decomposed into one or more
ACTIVITY-DECOMPOSITIONS.
- ACTIVITY-DECOMPOSITION: The specification of how an ACTIVITY is decomposed
into one or more SUB-ACTIVITIES; this may include the specification of
constraints on and between the SUB-ACTIVITIES
[and their TIME-INTERVALs].
- SUB-ACTIVITY: Sub-activities are the constituent activities
designated in any ACTIVITY-DECOMPOSITION.
- PRIMITIVE ACTIVITY is an ACTIVITY with no (further)
ACTIVITY-DECOMPOSITION.
- CONSTRAINTS can be stated with respect to none, one or more than
one time point. They express things which are required to hold.
They are evaluable with respect to a specific PLAN as
holding or not holding.
Such constraints may refer to world statements (conditions and effects),
resource requirements and usage, authority requirements or provision,
etc.
Level 2 Issues Remaining
Level 3: Aids to Specifying Activities
At this level, aids to enable the specification of activities and the
constraints on activities are to be provided. These are likely to
include:
- commonly used mechanisms for expressing activity orderings
(and-split, and-join, or-split, or-join, conditionals, etc), the
introduction of "dummy" nodes (to simplify ordering constraint
specification and user communication) or activities in an
activity-specification, etc.
Issue being considered by Austin Tate.
- relationship of terms like "resource", "authority", etc to the more
general definitions relating to states-of-affairs in levels 1 and 2.
Issue being considered by Austin Tate.
- A need to allow for annotations, outstanding issues, and
dependencies of various kinds to be recorded within plans.
Issue being considered by Austin Tate.