6.6.1 Plan monitoring

To monitor a plan, a request goal is posted in the database. This invokes an Initialize-Plan Act that computes the conditions that should be globally monitored for this plan and posts facts to the EA Manager database declaring that there is a current plan with monitors. These facts in turn cause Acts to execute in the EA Manager, which load and execute the plan. The EA Manager traverses through the parallel branches of this plan as missions complete.

The global monitors are computed using the API function compute-plan-monitoring-data, which can specify domain-specific monitors. Domain-independent capabilities are also available, such as having the system determine all predicates in plan preconditions that must be true initially (as opposed to predicates that are achieved by plan actions that precede them). In the SUO domain, compute-plan-monitoring-data finds all decision points and ``named areas of interest'' specified in the plan, and sets up monitors for them. This monitoring is accomplished by posting facts in the EA Manager database that cause the EA to notice any adversarial activity in these locations.

The EA can abort monitoring of one plan and switch to monitoring a new plan. This process involves removing facts for old missions and monitors from the EA Manager database, aborting execution of the Acts currently intended for execution, and posting a goal to execute the new plan.

Figure 5: Graphical representation of the Act that responds to every friendly location report.