Active Token: A token which has been activated in the partial plan. See the token state transition diagram for further details.
Base Domain: The maximal set of values a variable may take.
Closed World Assumption: An assumption that no new objects can be inserted into the partial plan. This assumption is enforceable in EUROPA, and leads to stronger propagation. For more information, see Dynamic Objects.
Compile Time Data: Those elements of a problem specification that are compiled prior to construction of a plan database, which remain static for the lifetime of a given plan database. Such data is typically considered the model. See the batch-solver process overview for further clarification.
DDL: Domain Description Language. Developed by Nicola Muscettola for the HSTS planner.
EUROPA: Extensible Reusable Remote Operations Planner. Refers to the planning technology platform consisting of a framework, a set of components, and a set of tools.
Grounded Plan: a plan in which all variables have been specified to a singleton value.
Plan Horizon: the temporal extent of the plan.
Inactive Token: A token which has been created in the plan database, either explicitly through an invocation by an external client, or implicitly through execution of a model rule instance. However, such a token has not yet been activated, merged or rejected. See the token state transition diagram for further details.
Interval Token: A token which has a duration of at least 1 time unit. All tokens on a class derived from Timeline are interval tokens.
Lower limit: Minimum boundary of a resource where the assumption is to produce early and consume late.
Master Token: An active token that has generated subgoals through rule instance execution.
Merged Token: A token which has been merged with an active token in the partial plan. See the token state transition diagram for further details.
Orphan Token: Any token that has been created by explicit request from a client external to the plan database. Such a token has no master.
Parameter Constraint: A constraint declared in the body of a NDDL predicate declaration. It can only apply to the immediate context of the predicate (i.e. built-in varaibles and user-defined predicate parameters). Parameter constraints apply to inactive and active tokens.
Partial Plan : a plan which is incomplete.
Plan Database: an object responsible for management of all entities in a partial plan. It provides operations for legal restrictions and relaxations to the partial plan and co-ordinates automated reasoning services to propagate consequences of such operations according to the domain-model and rules of inference of EUROPA.
Resource: A quantity which changes over time
Rejected Token: A token which has been rejected from the partial plan. See the token state transition diagram for further details.
Rule Instance: an instance of a model rule, scoped to a particular token and its subgoals.
Run-time Data: those elements of a problem specification that are created or deleted during the lifetime of a plan database. See the batch-solver process overview for further clarification.
Slave Token: Any token that has been created through rule instance execution.
Solver: A problem solving agent which conducts refinements to a partial plan until it is completed, has exhausted all possibilities, or has exhausted all its allocated time. For more information see solvers.
Specified Domain: indicates a subset of the base domain of a variable to which it has been specified by an external client.
Transaction: the act of producing or consuming a resource
Upper limit: Maximum bound of a resource where the assumption is to produce late and consume early.