Subactivity Theory
# Subactivity Theory

The PSL Ontology uses the `subactivity` relation
to capture the basic intuitions for the composition of activities.
The core theory subactivity.th alone does not specify any relationship
between the occurrence of an activity and occurrences of its subactivities.
For example, the specification of subactivities alone does not allow us to
distinguish between a nondeterministic activity and a deterministic activity.

The basic ontological commitments of the Subactivity Theory are based on the
following intuitions:

** Intuition 1:**

*
The composition relation is a discrete partial ordering, in which
primitive activities are the minimal elements.
*

## Informal Semantics for the Subactivity Theory

`(subactivity ?a1 ?a2)` is TRUE in an interpretation of Subactivity
Theory if and only if activity ?a1 is a subactivity of activity ?a2.

`(primitive ?a)` is TRUE in an interpretation of Subactivity Theory
if and only if the activity ?a has no proper subactivities.

Last Updated: Wednesday, 15-December-2003 11:42:40

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