KR2020Proceedings of the 17th International Conference on Principles of Knowledge Representation and ReasoningProceedings of the 17th International Conference on Principles of Knowledge Representation and Reasoning

Rhodes, Greece. September 12-18, 2020.

Edited by

ISSN: 2334-1033
ISBN: 978-0-9992411-7-2

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Copyright © 2020 International Joint Conferences on Artificial Intelligence Organization

On Sufficient and Necessary Conditions in Bounded CTL: A Forgetting Approach

  1. Renyan Feng(Guizhou University, P. R. China, Vrije Universiteit Amsterdam, The Netherlands)
  2. Erman Acar(Vrije Universiteit Amsterdam, The Netherlands)
  3. Stefan Schlobach(Vrije Universiteit Amsterdam, The Netherlands)
  4. Yisong Wang(Guizhou University, P. R. China)
  5. Wanwei Liu(National University of Defense Technology, P. R. China)


  1. Geometric, spatial, and temporal reasoning-General
  2. Knowledge representation languages-General
  3. Computational aspects of knowledge representation-General


Computation Tree Logic (CTL) is one of the central formalisms in formal verification. As a specification language, it is used to express a property that the system at hand is expected to satisfy. From both the verification and the system design points of view, some information content of such property might become irrelevant for the system due to

various reasons, e.g., it might become obsolete by time, or perhaps infeasible due to practical difficulties. Then, the problem arises on how to subtract such piece of information without altering the relevant system behaviour or violating the existing specifications over a given signature. Moreover, in such a scenario, two crucial notions are informative: the strongest necessary condition (SNC) and the weakest sufficient condition (WSC) of a given property. To address such a scenario in a principled way, we introduce a forgetting-based approach in CTL and show that it can be used to compute SNC and WSC of a property under a given model and over a given signature. We study its theoretical properties and also show that our notion of forgetting satisfies existing essential postulates of knowledge forgetting. Furthermore, we analyse the computational complexity of some basic reasoning tasks for the fragment CTLAF in particular.