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21
A computationally efficient approximation of DempsterShafer theory
, 1988
"... An often mentioned obstacle for the use of DempsterShafer theory for the handling of uncertainty in expert systems is the computational complexity of the theory. One cause of this complexity is the fact that in DempsterShafer theory the evidence is represented by a belief function which is induced ..."
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An often mentioned obstacle for the use of DempsterShafer theory for the handling of uncertainty in expert systems is the computational complexity of the theory. One cause of this complexity is the fact that in DempsterShafer theory the evidence is represented by a belief function which is induced by a basic probability assignment, i.e. a probability measure on the powerset of possible answers to a question, and not by a probability measure on the set of possible answers to a question, like in a Bayesian approach. In this paper, we define a Bayesian approximation of a belief function and show that combining the Bayesian approximations of belief functions is computationally less involving than combining the belief functions themselves, while in many practical applications replacing the belief functions by their Bayesian approximations will not essentially affect the result.
Cones and Foci for Protocol Verification Revisited
 In Proc. 6th Conference on Foundations of Software Science and Computation Structures, LNCS 2620
, 2003
"... Abstract. We define a cones and foci proof method, which rephrases the question whether two system specifications are branching bisimilar in terms of proof obligations on relations between data objects. Compared to the original cones and foci method from Groote and Springintveld [22], our method is ..."
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Abstract. We define a cones and foci proof method, which rephrases the question whether two system specifications are branching bisimilar in terms of proof obligations on relations between data objects. Compared to the original cones and foci method from Groote and Springintveld [22], our method is more generally applicable, and does not require a preprocessing step to eliminate τloops. We prove soundness of our approach and give an application. 1
Enhancing PartialOrder Reduction via Process Clustering
 In: Automated Software Engineering, ASE 2001, 16th. IEEE International Conference, Proceedings
, 2001
"... Partialorder reduction is a wellknown technique to cope with the statespaceexplosion problem in the verification of concurrent systems. Using the hierarchical structure of concurrent systems, we present an enhancement of the partialorderreduction scheme of [12, 19]. A prototype of the new algo ..."
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Cited by 5 (1 self)
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Partialorder reduction is a wellknown technique to cope with the statespaceexplosion problem in the verification of concurrent systems. Using the hierarchical structure of concurrent systems, we present an enhancement of the partialorderreduction scheme of [12, 19]. A prototype of the new algorithm has been implemented on top of the verification tool SPIN. The first experimental results are encouraging.
A complete axiomatisation of branching bisimulation for probabilistic systems with an application in protocol verification
 In Proceedings of the 17th International Conference on Concurrency Theory, volume 4137 of Lecture Notes in Computer Science
, 2006
"... Abstract. We consider abstraction in probabilistic process algebra. The process algebra can be employed for specifying processes that exhibit both probabilistic and nondeterministic choices in their behaviour. We give a set of axioms that completely axiomatises the branching bisimulation for the st ..."
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Abstract. We consider abstraction in probabilistic process algebra. The process algebra can be employed for specifying processes that exhibit both probabilistic and nondeterministic choices in their behaviour. We give a set of axioms that completely axiomatises the branching bisimulation for the strictly alternating probabilistic graph model. In addition, several recursive verification rules are identified, allowing us to remove redundant internal activity. Using the axioms and the verification rules, we have successfully conducted a verification of the Concurrent Alternating Bit Protocol. This is a simple communication protocol, slightly more ‘sophisticated ’ than the wellknown Alternating Bit Protocol. As channels are lossy, sending continuous streams of data through the channels is a method to overcome this possible loss of data. This instigates a considerable level of parallelism (parallel activities) and as such requires more complex techniques for proving the protocol correct. Using our process algebra we show that after abstraction of internal activity, the protocol behaves as a buffer. 1
1 MANUFACTURING A CARTESIAN CLOSED CATEGORY WITH EXACTLY TWO OBJECTS OUT OF A CMONOID
"... We answer a question of Lambek and Scott (see [LS] p.99) by proving the following: Theorem. Let 9vt be a Cmonoid, with Cstructure (7t, 7t', £, (_)*, <_,_>). Then there exists a cartesian closed category A with exactly two objects U and T, such that End(U) =!M The construction of. is en ..."
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We answer a question of Lambek and Scott (see [LS] p.99) by proving the following: Theorem. Let 9vt be a Cmonoid, with Cstructure (7t, 7t', £, (_)*, <_,_>). Then there exists a cartesian closed category A with exactly two objects U and T, such that End(U) =!M The construction of. is entirely by hand. The intuitive idea is as follows.!may be viewed as a collection of endomorphisms of a set U. Let T _ { *I be a onepoint set; then u X*.u is a onetoone correspondence between U and the set of all functions from T to U. Now if. is a cartesian closed category with just U and T for its objects, where T is terminal, then in A we must have Hom(U,U) = Hom(TxU,U) = Hom(T,UU) = _ Hom(T,U); so if we put Hom(U,U) = iM, and like to think of Hom(T,U) as HomSets({*},U), we must have M _ U, as sets. Since it does not matter much what the elements of U are, we take M=U. Then we have functions ft _ k*.f: ku.*:U{*}, we have (X*.f) o (ku.*) = ku f: U U. *I U for every f E U. Composing with o
Process Algebra with Language Matching
, 1994
"... An axiom system ACP ø lm is presented as a variant of the process algebra ACP (Algebra of Communicating Processes). The acronym ACP ø lm stands for ACP with abstraction, extended with operators and axioms for language matching . Language matching is a technique based on trace information for lab ..."
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An axiom system ACP ø lm is presented as a variant of the process algebra ACP (Algebra of Communicating Processes). The acronym ACP ø lm stands for ACP with abstraction, extended with operators and axioms for language matching . Language matching is a technique based on trace information for labelling and cutting off process terms that do not match some given trace (or set of traces). It is shown that in combination with the axioms for action alphabets interesting results are derivable, the most important of which is the Redundancy Theorem 3.3.6, which roughly states that if no trace labels occur in the expression @H (p l k q), where p l is a labelled version of some process p, then it holds that @H (p l k q) = @H (p k q). It is shown that under certain natural conditions a similar result holds when abstraction is applied to p l and p, respectively. As an example the Concurrent Alternating Bit Protocol (CABP) is verified. The CABP is a simple communication protocol, which can be re...
Cones and foci: A mechanical framework for protocol verification
, 2006
"... We define a cones and foci proof method, which rephrases the question whether two system specifications are branching bisimilar in terms of proof obligations on relations between data objects. Compared to the original cones and foci method from Groote and Springintveld, our method is more generall ..."
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We define a cones and foci proof method, which rephrases the question whether two system specifications are branching bisimilar in terms of proof obligations on relations between data objects. Compared to the original cones and foci method from Groote and Springintveld, our method is more generally applicable, because it does not require a preprocessing step to eliminate τloops. We prove soundness of our approach and present a set of rules to prove the reachability of focus points. Our method has been formalized and proved correct using PVS. Thus we have established a framework for mechanical protocol verification. We apply this framework to the Concurrent Alternating Bit Protocol.
The State Operator in Real Time Process Algebra
"... Abstract: We extend the real time process algebra of [BB91a] with the state operator of [BB88]. We show the usefulness of this extension in several examples. We use concepts from (classical) real space process algebra of [BB91b] in order to deal with different locations. ..."
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Abstract: We extend the real time process algebra of [BB91a] with the state operator of [BB88]. We show the usefulness of this extension in several examples. We use concepts from (classical) real space process algebra of [BB91b] in order to deal with different locations.