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Indefinitehorizon pomdps with actionbased termination
 In AAAI
, 2007
"... For decisiontheoretic planning problems with an indefinite horizon, plan execution terminates after a finite number of steps with probability one, but the number of steps until termination (i.e., the horizon) is uncertain and unbounded. In the traditional approach to modeling such problems, called ..."
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For decisiontheoretic planning problems with an indefinite horizon, plan execution terminates after a finite number of steps with probability one, but the number of steps until termination (i.e., the horizon) is uncertain and unbounded. In the traditional approach to modeling such problems, called a stochastic shortestpath problem, plan execution terminates when a particular state is reached, typically a goal state. We consider a model in which plan execution terminates when a stopping action is taken. We show that an actionbased model of termination has several advantages for partially observable planning problems. It does not require a goal state to be fully observable; it does not require achievement of a goal state to be guaranteed; and it allows a proper policy to be found more easily. This framework allows many partially observable planning problems to be modeled in a more realistic way that does not require an artificial discount factor.
Confirming configurations in EFSM
 In Proc. IFIP Joint Int’l Conf. FORTE/PSTV
, 1999
"... In this paper we investigate the problem of configuration distinguishability for the EFSM model, specifically, given a configuration and an arbitrary set of configurations, determine an input sequence such that the EFSM in the given configuration produces an output sequence different from that of th ..."
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In this paper we investigate the problem of configuration distinguishability for the EFSM model, specifically, given a configuration and an arbitrary set of configurations, determine an input sequence such that the EFSM in the given configuration produces an output sequence different from that of the configurations in the given set or at least in a maximal proper subset. Such a sequence can be used in a test case to confirm the destination configuration. We demonstrate that the distinguishability problem could be reduced to the EFSM traversal problem, so that the existing methods and tools developed in the context of model checking become applicable. The theoretical framework for determining configurationconfirming sequences based on projections and products of EFSMs is presented. Our approach can be implemented in a number of heuristic test derivation strategies.
Timed Testing under Partial Observability
, 2009
"... This paper studies the problem of modelbased testing of realtime systems that are only partially observable. We model the System Under Test (SUT) using Timed Game Automata (TGA) which has internal actions, uncontrollable outputs and timing uncertainty of outputs. We define the partial observabilit ..."
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This paper studies the problem of modelbased testing of realtime systems that are only partially observable. We model the System Under Test (SUT) using Timed Game Automata (TGA) which has internal actions, uncontrollable outputs and timing uncertainty of outputs. We define the partial observability of SUT using a set of predicates over the TGA state space, and specify the test purposes in Computation Tree Logic (CTL) formulas. A recently developed partially observable timed game solver is used to generate winning strategies, which are used as test cases. We propose a conformance testing framework, define a partial observationbased conformance relation, present the test execution algorithms, and prove the soundness and completeness of this test method (i.e., a detected error really violates the conformance relation; and if the SUT violates the test purpose, then a test case can be generated to detect this violation). Experiments on some nontrivial examples show that this method yields encouraging results.
Test Generation Driven by Userdefined Fault models
 Proceedings of the Twelfth International Workshop on Testing of Communicating Systems
, 1999
"... In this paper, we consider the problem of test derivation from a specification FSM, assuming that all possible implementation FSMs are submachines of some nondeterministic FSM. The latter represents a restricted class of faults defined by the user. The state number in an implementation may exceed ..."
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Cited by 6 (2 self)
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In this paper, we consider the problem of test derivation from a specification FSM, assuming that all possible implementation FSMs are submachines of some nondeterministic FSM. The latter represents a restricted class of faults defined by the user. The state number in an implementation may exceed that of the specification. We present a method for test generation that can deliver shorter tests than the other existing methods. The method is also more flexible than the traditional FSMbased methods, which embody a universal fault model defined only by a state number.
Probabilistic ωAutomata
, 2012
"... Probabilistic ωautomata are variants of nondeterministic automata over infinite words where all choices are resolved by probabilistic distributions. Acceptance of a run for an infinite input word can be defined using traditional acceptance criteria for ωautomata, such as Büchi, Rabin or Streett c ..."
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Probabilistic ωautomata are variants of nondeterministic automata over infinite words where all choices are resolved by probabilistic distributions. Acceptance of a run for an infinite input word can be defined using traditional acceptance criteria for ωautomata, such as Büchi, Rabin or Streett conditions. The accepted language of a probabilistic ωautomata is then defined by imposing a constraint on the probability measure of the accepting runs. In this paper, we study a series of fundamental properties of probabilistic ωautomata with three different languagesemantics: (1) the probable semantics that requires positive acceptance probability, (2) the almostsure semantics that requires acceptance with probability 1, and (3) the threshold semantics that relies on an additional parameter λ ∈]0, 1 [ that specifies a lower probability bound for the acceptance probability. We provide a comparison of probabilistic ωautomata under these three semantics and nondeterministic ωautomata concerning expressiveness and efficiency. Furthermore, we address closure properties under the Boolean operators union, intersection and complementation and algorithmic aspects, such as checking emptiness or language containment.
State identification problems for timed automata
 Proc. of the 17th IFIP Int’l Conf. on Testing of Communicating Systems (TestCom 2005). LNCS 3502
, 2005
"... Abstract. A wellestablished theory exists for testing finite state machines. One fundamental class of problems handled by this theory is state identification: we are given a machine with known state space and transition relation, but unknown initial state, and we are asked to find tests which ident ..."
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Abstract. A wellestablished theory exists for testing finite state machines. One fundamental class of problems handled by this theory is state identification: we are given a machine with known state space and transition relation, but unknown initial state, and we are asked to find tests which identify the initial or final state of the machine. In this paper, we study state identification in the context of timed automata which contrary to, say, Mealy or Moore machines, is a suitable model for realtime systems. We are interested in digitalclock tests which have a finite clock precision and are thus implementable. We develop a general technique, based on timeabstracting bisimulation, which reduces the problem to the case of nondeterministic finitestate Mealy machines. We illustrate our technique on a toy example. 1
Using model counting to find optimal distinguishing tests
 In Proc. of COUNTING’08
, 2008
"... Abstract. Testing is the process of stimulating a system with inputs in order to reveal hidden parts of the system state. In the case of nondeterministic systems, the difficulty arises that an input pattern can generate several possible outcomes. Some of these outcomes allow to distinguish between ..."
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Abstract. Testing is the process of stimulating a system with inputs in order to reveal hidden parts of the system state. In the case of nondeterministic systems, the difficulty arises that an input pattern can generate several possible outcomes. Some of these outcomes allow to distinguish between different hypotheses about the system state, while others do not. In this paper, we present a novel approach to find, for nondeterministic systems modeled as constraints over variables, tests that allow to distinguish among the hypotheses as good as possible. The idea is to assess the quality of a test by determining the ratio of distinguishing (good) and not distinguishing (bad) outcomes. This measure refines previous notions proposed in the literature on modelbased testing and can be computed using model counting techniques. We propose and analyze a greedytype algorithm to solve this test optimization problem, using existing model counters as a building block. We give preliminary experimental results of our method, and discuss possible improvements. 1
Combining ModelBased Testing and Runtime Monitoring for Program Testing in the Presence of Nondeterminism
"... Abstract—In case of underspecified or not fully predictable systems, models specifying system behaviors are nondeterministic. Nondeterminism poses several challenges for the validation and verification activities, including the problem of inconclusive tests in modelbased testing with model checker. ..."
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Abstract—In case of underspecified or not fully predictable systems, models specifying system behaviors are nondeterministic. Nondeterminism poses several challenges for the validation and verification activities, including the problem of inconclusive tests in modelbased testing with model checker. It is a validation technique that use model checker counterexamples as test cases. In this paper, we tackle the problem of testing nondeterministic systems by combining modelbased testing and runtime conformance monitoring: the input sequences of the tests are automatically generated from nondeterministic models; then their execution is runtime monitored to check conformance of the code w.r.t. its specification. This technique provides an oracle for the test data, it never bears inconclusive responses, and it allows measuring the requirement coverage. The approach uses the Abstract State Machines as formal method for specification purposes and Java as implementation language. As a proof of concepts, the TicTacToe game is taken as example of a system with nondeterministic behavior (both at specification and code levels). I.
Regression testing process improvement for specification evolution of realworld protocol software
 in: Proceedings of the 10th International Conference on Quality Software (QSIC 2010), IEEE Computer Society Press, Los Alamitos, CA
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Mutation Testing from Probabilistic and Stochastic Finite State Machines
 Journal of Systems and Software
, 2009
"... Specification mutation involves mutating a specification, and for each mutation a test is derived that distinguishes the behaviours of the mutated and original specifications. This approach has been applied with finite state machines based models. This paper extends mutation testing to finite state ..."
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Specification mutation involves mutating a specification, and for each mutation a test is derived that distinguishes the behaviours of the mutated and original specifications. This approach has been applied with finite state machines based models. This paper extends mutation testing to finite state machine models that contain nonfunctional properties. The paper describes several ways of mutating a finite state machine with probabilities (PFSM) or stochastic time (PSFSM) attached to their transitions and shows how test sequences that distinguish between them and their mutants can be generated. Testing then involves applying each test sequence multiple times, observing the resultant output sequences and using results from statistical sampling theory in order to compare the observed frequency of each output sequence with that expected. Key words: mutation testing; probabilities; stochastic time; specification mutation 1