Authors:
Andreas Lanz
1
;
Roberto Posenato
2
;
Carlo Combi
2
and
Manfred Reichert
3
Affiliations:
1
University of Ulm, Germany
;
2
University of Verona, Italy
;
3
Ulm University, Germany
Keyword(s):
Simple Temporal Constraint Network with Uncertainty, STNU, Controllability, Guarded Constraints.
Related
Ontology
Subjects/Areas/Topics:
Agents
;
Artificial Intelligence
;
Constraint Satisfaction
;
Formal Methods
;
Informatics in Control, Automation and Robotics
;
Intelligent Control Systems and Optimization
;
Planning and Scheduling
;
Simulation and Modeling
;
Symbolic Systems
;
Task Planning and Execution
Abstract:
The Simple Temporal Network with Uncertainty (STNU) model focuses on the representation and evaluation
of temporal constraints on time-point variables (timepoints), of which some (i.e., contingent timepoints) cannot
be assigned (i.e., executed by the system), but only be observed. Moreover, a temporal constraint is expressed
as an admissible range of delays between two timepoints. Regarding the STNU model, it is interesting to
determine whether it is possible to execute all the timepoints under the control of the system, while still
satisfying all given constraints, no matter when the contingent timepoints happen within the given time ranges
(controllability check). Existing approaches assume that the original contingent time range cannot be modified
during execution. In real world, however, the allowed time range may change within certain boundaries, but
cannot be completely shrunk. To represent such possibility more properly, we propose Simple Temporal
Network with Partially Shrink
able Uncertainty (STNPSU) as an extension of STNU. In particular, STNPSUs
allow representing a contingent range in a way that can be shrunk during run time as long as shrinking does
not go beyond a given threshold. We further show that STNPSUs allow representing STNUs as a special case,
while maintaining the same efficiency for both controllability checks and execution.
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