Tableaux and witnesses for the my--calculus

Symbolic temporal logic model checking is an automatic verification method. One of its main features is that a counterexample can be constructed when a temporal formula does not hold for the model. Most model checkers so far have restricted the type of formulae that can be checked and for which counterexamples can be constructed to fair CTL formulae. This paper shows how counterexamples and witnesses for the whole µ-Calculus can be constructed. The witness construction presented in this paper is polynomial in the model and the formula

Local model checking in Park\u27s my--calculus

Temporal logic model checking is an automatic verification method for finite-state systems. In global model checking, the truth of a formula (and its subformulae) is determined for all the states in the model. Local model checking procedures are designed for proving that a specific state of the model satisfies a given formula. This may avoid the exhaustive traversal of a model. Also, the proof tree constructed during local model checking can serve as a witness (counterexample) which demonstrates the error in the design and can thus help locating errors. In \cite{StiWal91} it was shown how local model checking can be performed in the modal $\mu$-calculus. In this paper, we introduce a tableau system and thus a local model checking method for the more expressive $\mu$-calculus of Park \cite{Par76} and prove its soundness and completeness

Formula dependent model reduction through elimination of invisible transitions for checking fragments of CTL

We present a reduction algorithm which reduces Kripke structures by eliminating transitions from the model which do not affect the visible components of the model. These are exactly the variables contained in the specification formula. The reduction algorithm preserves the truth of special CTL formulae. In contrast to formula-dependent reduction algorithms presented so far, which are mostly computationally expensive, our algorithm needs only one pass through the reachable states of the model. Nevertheless, preliminary results show that models are reduced considerably, which is plausible because, in general, the number of visible components of a reactive system is small compared to the number of internal components

Generation of counterexamples for the my--calculus

Symbolic temporal logic model checking is an automatic verification method. One of its main features is that a counterexample can be constructed when a temporal formula does not hold for the model. Most model checkers so far have restricted the type of formulae that can be checked to fair CTL formulae. Model checkers constructed just recently can check arbitrary $\mu$-calculus formulae. How to construct counterexamples for arbitrary \muf has not been investigated yet. This paper shows how counterexamples and witnesses for the whole $\mu$-calculus can be constructed

From tableaux to witnesses for the my--calculus

Symbolic temporal logic model checking is an automatic verification method. One of its main features is that a counterexample can be constructed when a temporal formula does not hold for the model. Most model checkers so far have restricted the type of formulae that can be checked and for which counterexamples can be constructed to fair CTL formulae. This paper shows how counterexamples and witnesses for the whole µ-Calculus can be constructed. The witness construction is derived in a formal way from the local model checking method. The witness construction presented in this paper is polynomial in the model and the formula

Reduced witnesses for the my--calculus

Symbolic temporal logic model checking is an automatic verification method. One of its main features is that a counterexample can be constructed when a temporal formula does not hold for the model. Most model checkers so far have restricted the type of formulae that can be checked and for which counterexamples can be constructed to fair CTL formulae. In a previous paper, we have presented an algorithm which constructs counterexamples and witnesses for the whole µ-Calculus. The witnesses constructed by this algorithm can be huge, however. In this paper, we show how to construct reduced witnesses

A case study on different modelling approaches based on model checking - verifying numerous versions of the alternating bit protocol with SMV

Recently, outstanding results have been achieved in the formal verification of concurrent systems by model checking techniques. In this paper we report our experience with SMV, a symbolic model verifier, applied to a communication protocol, the alternating bit protocol. We investigated different approaches of modeling the alternating bit protocol in SMV. We describe the problems encountered because of the restrictions of SMV. As a consequence, we call for a more general language for model checking, which both overcomes these disadvantages of SMV and enhances the possibility of optimizations, and more specific input languages on top of it, easing the application of model checking for the end user

Induction of Immune Mediators in Glioma and Prostate Cancer Cells by Non-Lethal Photodynamic Therapy

BACKGROUND: Photodynamic therapy (PDT) uses the combination of photosensitizing drugs and harmless light to cause selective damage to tumor cells. PDT is therefore an option for focal therapy of localized disease or for otherwise unresectable tumors. In addition, there is increasing evidence that PDT can induce systemic anti-tumor immunity, supporting control of tumor cells, which were not eliminated by the primary treatment. However, the effect of non-lethal PDT on the behavior and malignant potential of tumor cells surviving PDT is molecularly not well defined. METHODOLOGY/PRINCIPAL FINDINGS: Here we have evaluated changes in the transcriptome of human glioblastoma (U87, U373) and human (PC-3, DU145) and murine prostate cancer cells (TRAMP-C1, TRAMP-C2) after non-lethal PDT in vitro and in vivo using oligonucleotide microarray analyses. We found that the overall response was similar between the different cell lines and photosensitizers both in vitro and in vivo. The most prominently upregulated genes encoded proteins that belong to pathways activated by cellular stress or are involved in cell cycle arrest. This response was similar to the rescue response of tumor cells following high-dose PDT. In contrast, tumor cells dealing with non-lethal PDT were found to significantly upregulate a number of immune genes, which included the chemokine genes CXCL2, CXCL3 and IL8/CXCL8 as well as the genes for IL6 and its receptor IL6R, which can stimulate proinflammatory reactions, while IL6 and IL6R can also enhance tumor growth. CONCLUSIONS: Our results indicate that PDT can support anti-tumor immune responses and is, therefore, a rational therapy even if tumor cells cannot be completely eliminated by primary phototoxic mechanisms alone. However, non-lethal PDT can also stimulate tumor growth-promoting autocrine loops, as seen by the upregulation of IL6 and its receptor. Thus the efficacy of PDT to treat tumors may be improved by controlling unwanted and potentially deleterious growth-stimulatory pathways

Local Model Checking in Park's µ-Calculus

Temporal logic model checking is a verification method for reactive systems. In global model checking, the truth of a formula (and its subformulae) is determined for all the states in the model. Local model checking procedures are designed for proving that a specific state of the model satisfies a given formula. This may avoid the exhaustive traversal of a model and can thus be applied also to infinite models. Also, the proof tree constructed during local model checking can serve as a witness (counterexample) which demonstrates the error in the design and can thus help locating errors. In this paper, we introduce a tableau system and thus a local model checking method for the µ-calculus of Park [1] and prove its soundness and completeness

Local Model Checking in Park's µ-Calculus

Temporal logic model checking is an automatic verification method for finite-state systems. In global model checking, the truth of a formula (and its subformulae) is determined for all the states in the model. Local model checking procedures are designed for proving that a specific state of the model satisfies a given formula. This may avoid the exhaustive traversal of a model. Also, the proof tree constructed during local model checking can serve as a witness (counterexample) which demonstrates the error in the design and can thus help locating errors. In [SW91] it was shown how local model checking can be performed in the modal ¯-calculus. In this paper, we introduce a tableau system and thus a local model checking method for the more expressive ¯-calculus of Park [Par76] and prove its soundness and completeness. 1 Introduction In the last twenty years many approaches to program verification have been developed. Hoare's partial correctness logic for simple while programs gave an ea..