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Pattern backtracking algorithm for the workflow satisfiability problem with user-independent constraints

Karapetyan, D and Gagarin, A and Gutin, G (2015) Pattern backtracking algorithm for the workflow satisfiability problem with user-independent constraints. In: Frontiers in Algorithmics. FAW 2015., 2015-07-03 - 2015-07-05, Guilin, China.

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Abstract

The workflow satisfiability problem (WSP) asks whether there exists an assignment of authorised users to the steps in a workflow specification, subject to certain constraints on the assignment. (Such an assignment is called valid.) The problem is NP-hard even when restricted to the large class of user-independent constraints. Since the number of steps k is relatively small in practice, it is natural to consider a parametrisation of the WSP by k. We propose a new fixed-parameter algorithm to solve the WSP with user-independent constraints. The assignments in our method are partitioned into equivalence classes such that the number of classes is exponential in k only. We show that one can decide, in polynomial time, whether there is a valid assignment in an equivalence class. By exploiting this property, our algorithm reduces the search space to the space of equivalence classes, which it browses within a backtracking framework, hence emerging as an efficient yet relatively simple-to-implement or generalise solution method. We empirically evaluate our algorithm against the state-of-the-art methods and show that it clearly wins the competition on the whole range of our test problems and significantly extends the domain of practically solvable instances of the WSP.

Item Type: Conference or Workshop Item (Paper)
Additional Information: Published proceedings: Frontiers in Algorithmics 9th International Workshop, FAW 2015, Guilin, China, July 3-5, 2015, Proceedings. Part of the Lecture Notes in Computer Science book series (LNCS, volume 9130)
Subjects: Q Science > QA Mathematics
Q Science > QA Mathematics > QA75 Electronic computers. Computer science
Divisions: Faculty of Science and Health > Computer Science and Electronic Engineering, School of
Depositing User: Elements
Date Deposited: 24 May 2018 13:27
Last Modified: 24 May 2018 13:27
URI: http://repository.essex.ac.uk/id/eprint/22106

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