University of Konstanz

Displaying 1-23 of 23 results

  • White Papers // May 2012

    Causality Checking for Complex System Models

    The authors present an approach for the algorithmic computation of causalities in system models that they refer to as causality checking. They are basing their notion of causality on counterfactual reasoning, in particular using the structural equation model approach proposed in that has been extended to reasoning about computational models...

    Provided By University of Konstanz

  • White Papers // Mar 2012

    Analysis of an Airport Surveillance Radar Using the QuantUM Approach

    The authors report on the modeling and formal analysis of reliability requirements in the context of an Airport Surveillance Radar system using SysML and probabilistic model checking. The system is modeled using the QuantUM modeling tool which uses the PRISM model checker as an analysis back-end. They illustrate how a...

    Provided By University of Konstanz

  • White Papers // Jan 2012

    Towards Causality Checking for Complex System Models

    With the increasing growth of the size and complexity of modern safety-critical systems, the demand for model based engineering methods that both help in architecting such systems and to asses their safety and correctness becomes increasingly obvious. Causality checking is an automated method for formal causality analysis of system models...

    Provided By University of Konstanz

  • White Papers // Dec 2011

    CTL: A Platform-Independent Crypto Tools Library Based on Dataflow Programming Paradigm

    The diversity of computing platforms is increasing rapidly. In order to allow security applications to run on such diverse platforms, implementing and optimizing the same cryptographic primitives for multiple target platforms and heterogeneous systems can result in high costs. In this paper, the authors report their efforts in developing and...

    Provided By University of Konstanz

  • White Papers // Jun 2011

    From Probabilistic Counterexamples Via Causality to Fault Trees

    In recent years, several approaches to generate probabilistic counterexamples have been proposed. The interpretation of stochastic counterexamples, however, continues to be problematic since they have to be represented as sets of paths, and the number of paths in this set may be very large. Fault Trees (FTs) are a well-established...

    Provided By University of Konstanz

  • White Papers // May 2011

    DiPro - A Tool for Probabilistic Counterexample Generation

    The computation of counterexamples for probabilistic model checking has been an area of active research over the past years. In spite of the achieved theoretical results in this field, there is no freely available tool that allows for the computation and representation of probabilistic counterexamples. The authors present an open...

    Provided By University of Konstanz

  • White Papers // May 2011

    Modeling and Analyzing Spike Timing Dependent Plasticity With Linear Hybrid Automata

    The authors propose a model for synaptic plasticity according to the Spike Timing Dependent Plasticity (STDP) theory using Linear Hybrid Automata (LHA). They first present a compositional LHA model in which each component corresponds to some process in STDP. They then abstract this model into a monolithic LHA model in...

    Provided By University of Konstanz

  • White Papers // May 2011

    Market Liberalization, Regulatory Uncertainty, And Firm Investment

    Motivated by the German postal market, this paper analyzes the effects of regulatory uncertainty about labor costs for investment into a liberalized market. The authors distinguish between the external investment margin (market entry) and the internal investment margin (technology) and establish that regulatory uncertainty affects these margins differently, encouraging market...

    Provided By University of Konstanz

  • White Papers // Apr 2011

    Is German Domestic Social Policy Politically Controversial?

    This paper investigates empirically the influence of government ideology on social policy using German data. Examining the funding and the benefits of social security and public healthcare policy, the author's results suggest that policies implemented by governments dominated by left- and rightwing parties were similar over the 1951-2007 period. Leftwing...

    Provided By University of Konstanz

  • White Papers // Apr 2011

    Unemployment, Human Capital Depreciation And Pension Benefits: An Empirical Evaluation Of German Data

    This paper investigates empirically how unemployment-induced employment-breaks at different career stages influence pension benefits. The analysis is based on German data. The author distinguishes four different career phases and investigates to what extent the prevailing social security policy compensated for earning losses. The results suggest that losses in pension benefits...

    Provided By University of Konstanz

  • White Papers // Feb 2011

    The QuantUM Approach in the Context of the ISO Standard 26262 for Automotive Systems

    The forthcoming standard ISO 26262 defines processes and techniques in support of a safe design and implementation of automotive systems. The authors comment on the recommendations that this standard provides with respect to the use of semi-formal and formal methods, including formal verification, during various stages of the proposed safety...

    Provided By University of Konstanz

  • White Papers // Feb 2011

    QuantUM: Quantitative Safety Analysis of UML Models

    When developing a safety-critical system it is essential to obtain an assessment of different design alternatives. In particular, an early safety assessment of the architectural design of a system is desirable. In spite of the plethora of available formal quantitative analysis methods it is still difficult for software and system...

    Provided By University of Konstanz

  • White Papers // Jan 2011

    Quantitative Analysis of UML Models

    When developing a safety-critical system it is essential to obtain an assessment of different design alternatives. In particular, an early safety assessment of the architectural design of a system is desirable. In spite of the plethora of available formal quantitative analysis methods it is still difficult for software and system...

    Provided By University of Konstanz

  • White Papers // Jan 2011

    Efficient Firm Dynamics In A Frictional Labor Market

    The introduction of firm size into labor search models raises the question how wages are set when average and marginal product differs. The authors develop and analyze an alternative to the existing bargaining framework: firms compete for labor by publicly posting long-term contracts. In such a competitive search setting, firms...

    Provided By University of Konstanz

  • White Papers // Sep 2010

    Endogenous Credit Constraints, Human Capital Investment And Optimal Tax Policy

    This paper employs a two-period life-cycle model to derive the optimal tax policy when educational investments are subject to credit constraints. Credit constraints arise from the limited commitment of debtors to repay loans and are endogenously determined by private banks under the non-default condition that individuals cannot be better off...

    Provided By University of Konstanz

  • White Papers // Sep 2010

    Integer Linear Programming Based Property Checking for Asynchronous Reactive Systems

    Asynchronous reactive systems form the basis of a wide range of software systems, for instance in the telecommunications domain. It is highly desirable to rigorously show that these systems are correctly designed. However, traditional formal approaches to the verification of these systems are often difficult because asynchronous reactive systems usually...

    Provided By University of Konstanz

  • White Papers // Jun 2010

    Extending Non-Termination Proof Techniques to Asynchronously Communicating Concurrent Programs

    Currently, no approaches are known that allow for non-termination proofs of concurrent programs which account for asynchronous communication via FIFO message queues. Those programs may be written in high-level languages such as Java or Promela. The authors present a first approach to prove non-termination for such programs. In addition to...

    Provided By University of Konstanz

  • White Papers // Nov 2009

    Automated Predicate Abstraction for Real-Time Models

    Model checking has been widely successful in validating and debugging hardware designs and communication protocols. However, state-space explosion is an intrinsic problem which limits the applicability of model checking tools. To overcome this limitation software model checkers have suggested different approaches, among which abstraction methods have been highly esteemed. Modern...

    Provided By University of Konstanz

  • White Papers // Jul 2009

    Generation of Counterexamples for Model Checking of Markov Decision Processes

    The practical usefulness of a model checker as a debugging tool relies on its ability to provide diagnostic information, sometimes also referred to as a counterexample. Current stochastic model checkers do not provide such diagnostic information. In this paper, the authors address this problem for Markov Decision Processes. First, they...

    Provided By University of Konstanz

  • White Papers // Jun 2009

    Safety Analysis of an Airbag System Using Probabilistic FMEA and Probabilistic Counterexamples

    Failure Mode and Effects Analysis (FMEA) is a technique to reason about possible system hazards that result from system or system component failures. Traditionally, FMEA does not take the probabilities with which these failures may occur into account. Recently, this shortcoming was addressed by integrating stochastic model checking techniques into...

    Provided By University of Konstanz

  • White Papers // May 2009

    Directed Explicit State-Space Search in the Generation of Counterexamples for Stochastic Model Checking

    Current stochastic model checkers do not make counterexamples for property violations readily available. In this paper, the authors apply directed explicit state space search to discrete- and continuous-time Markov chains in order to compute counterexamples for the violation of PCTL or CSL properties. Directed explicit state space search algorithms explore...

    Provided By University of Konstanz

  • White Papers // May 2009

    K*: Heuristics-Guided, On-the-Fly k Shortest Paths Search

    In this paper, the authors consider the K-Shortest-Paths Problem (KSP) which is about finding the k shortest paths from a start vertex s to a target vertex t in a directed weighted graph G for an arbitrary natural number k. Application domain examples for KSP problems include logistics, finance analysis,...

    Provided By University of Konstanz

  • White Papers // May 2009

    Heuristic Search for Unbounded Executions

    The authors present a heuristic search based approach to finding un-bounded executions in software models that can be described using Communicating Finite State Machines (CFSMs). This improves the unboundedness test devised by Jeron and Jard in case certain knowledge about potential sources of unboundedness is available. Such knowledge can be...

    Provided By University of Konstanz

  • White Papers // May 2009

    K*: Heuristics-Guided, On-the-Fly k Shortest Paths Search

    In this paper, the authors consider the K-Shortest-Paths Problem (KSP) which is about finding the k shortest paths from a start vertex s to a target vertex t in a directed weighted graph G for an arbitrary natural number k. Application domain examples for KSP problems include logistics, finance analysis,...

    Provided By University of Konstanz

  • White Papers // May 2009

    Heuristic Search for Unbounded Executions

    The authors present a heuristic search based approach to finding un-bounded executions in software models that can be described using Communicating Finite State Machines (CFSMs). This improves the unboundedness test devised by Jeron and Jard in case certain knowledge about potential sources of unboundedness is available. Such knowledge can be...

    Provided By University of Konstanz

  • White Papers // May 2009

    Directed Explicit State-Space Search in the Generation of Counterexamples for Stochastic Model Checking

    Current stochastic model checkers do not make counterexamples for property violations readily available. In this paper, the authors apply directed explicit state space search to discrete- and continuous-time Markov chains in order to compute counterexamples for the violation of PCTL or CSL properties. Directed explicit state space search algorithms explore...

    Provided By University of Konstanz

  • White Papers // Nov 2009

    Automated Predicate Abstraction for Real-Time Models

    Model checking has been widely successful in validating and debugging hardware designs and communication protocols. However, state-space explosion is an intrinsic problem which limits the applicability of model checking tools. To overcome this limitation software model checkers have suggested different approaches, among which abstraction methods have been highly esteemed. Modern...

    Provided By University of Konstanz

  • White Papers // Jul 2009

    Generation of Counterexamples for Model Checking of Markov Decision Processes

    The practical usefulness of a model checker as a debugging tool relies on its ability to provide diagnostic information, sometimes also referred to as a counterexample. Current stochastic model checkers do not provide such diagnostic information. In this paper, the authors address this problem for Markov Decision Processes. First, they...

    Provided By University of Konstanz

  • White Papers // Jun 2009

    Safety Analysis of an Airbag System Using Probabilistic FMEA and Probabilistic Counterexamples

    Failure Mode and Effects Analysis (FMEA) is a technique to reason about possible system hazards that result from system or system component failures. Traditionally, FMEA does not take the probabilities with which these failures may occur into account. Recently, this shortcoming was addressed by integrating stochastic model checking techniques into...

    Provided By University of Konstanz

  • White Papers // Mar 2012

    Analysis of an Airport Surveillance Radar Using the QuantUM Approach

    The authors report on the modeling and formal analysis of reliability requirements in the context of an Airport Surveillance Radar system using SysML and probabilistic model checking. The system is modeled using the QuantUM modeling tool which uses the PRISM model checker as an analysis back-end. They illustrate how a...

    Provided By University of Konstanz

  • White Papers // Jan 2012

    Towards Causality Checking for Complex System Models

    With the increasing growth of the size and complexity of modern safety-critical systems, the demand for model based engineering methods that both help in architecting such systems and to asses their safety and correctness becomes increasingly obvious. Causality checking is an automated method for formal causality analysis of system models...

    Provided By University of Konstanz

  • White Papers // Jun 2011

    From Probabilistic Counterexamples Via Causality to Fault Trees

    In recent years, several approaches to generate probabilistic counterexamples have been proposed. The interpretation of stochastic counterexamples, however, continues to be problematic since they have to be represented as sets of paths, and the number of paths in this set may be very large. Fault Trees (FTs) are a well-established...

    Provided By University of Konstanz

  • White Papers // May 2011

    DiPro - A Tool for Probabilistic Counterexample Generation

    The computation of counterexamples for probabilistic model checking has been an area of active research over the past years. In spite of the achieved theoretical results in this field, there is no freely available tool that allows for the computation and representation of probabilistic counterexamples. The authors present an open...

    Provided By University of Konstanz

  • White Papers // May 2011

    Modeling and Analyzing Spike Timing Dependent Plasticity With Linear Hybrid Automata

    The authors propose a model for synaptic plasticity according to the Spike Timing Dependent Plasticity (STDP) theory using Linear Hybrid Automata (LHA). They first present a compositional LHA model in which each component corresponds to some process in STDP. They then abstract this model into a monolithic LHA model in...

    Provided By University of Konstanz

  • White Papers // Feb 2011

    The QuantUM Approach in the Context of the ISO Standard 26262 for Automotive Systems

    The forthcoming standard ISO 26262 defines processes and techniques in support of a safe design and implementation of automotive systems. The authors comment on the recommendations that this standard provides with respect to the use of semi-formal and formal methods, including formal verification, during various stages of the proposed safety...

    Provided By University of Konstanz

  • White Papers // Feb 2011

    QuantUM: Quantitative Safety Analysis of UML Models

    When developing a safety-critical system it is essential to obtain an assessment of different design alternatives. In particular, an early safety assessment of the architectural design of a system is desirable. In spite of the plethora of available formal quantitative analysis methods it is still difficult for software and system...

    Provided By University of Konstanz

  • White Papers // Jan 2011

    Quantitative Analysis of UML Models

    When developing a safety-critical system it is essential to obtain an assessment of different design alternatives. In particular, an early safety assessment of the architectural design of a system is desirable. In spite of the plethora of available formal quantitative analysis methods it is still difficult for software and system...

    Provided By University of Konstanz

  • White Papers // Sep 2010

    Integer Linear Programming Based Property Checking for Asynchronous Reactive Systems

    Asynchronous reactive systems form the basis of a wide range of software systems, for instance in the telecommunications domain. It is highly desirable to rigorously show that these systems are correctly designed. However, traditional formal approaches to the verification of these systems are often difficult because asynchronous reactive systems usually...

    Provided By University of Konstanz

  • White Papers // Jun 2010

    Extending Non-Termination Proof Techniques to Asynchronously Communicating Concurrent Programs

    Currently, no approaches are known that allow for non-termination proofs of concurrent programs which account for asynchronous communication via FIFO message queues. Those programs may be written in high-level languages such as Java or Promela. The authors present a first approach to prove non-termination for such programs. In addition to...

    Provided By University of Konstanz

  • White Papers // Jan 2011

    Efficient Firm Dynamics In A Frictional Labor Market

    The introduction of firm size into labor search models raises the question how wages are set when average and marginal product differs. The authors develop and analyze an alternative to the existing bargaining framework: firms compete for labor by publicly posting long-term contracts. In such a competitive search setting, firms...

    Provided By University of Konstanz

  • White Papers // Apr 2011

    Unemployment, Human Capital Depreciation And Pension Benefits: An Empirical Evaluation Of German Data

    This paper investigates empirically how unemployment-induced employment-breaks at different career stages influence pension benefits. The analysis is based on German data. The author distinguishes four different career phases and investigates to what extent the prevailing social security policy compensated for earning losses. The results suggest that losses in pension benefits...

    Provided By University of Konstanz

  • White Papers // Apr 2011

    Is German Domestic Social Policy Politically Controversial?

    This paper investigates empirically the influence of government ideology on social policy using German data. Examining the funding and the benefits of social security and public healthcare policy, the author's results suggest that policies implemented by governments dominated by left- and rightwing parties were similar over the 1951-2007 period. Leftwing...

    Provided By University of Konstanz

  • White Papers // May 2011

    Market Liberalization, Regulatory Uncertainty, And Firm Investment

    Motivated by the German postal market, this paper analyzes the effects of regulatory uncertainty about labor costs for investment into a liberalized market. The authors distinguish between the external investment margin (market entry) and the internal investment margin (technology) and establish that regulatory uncertainty affects these margins differently, encouraging market...

    Provided By University of Konstanz

  • White Papers // Sep 2010

    Endogenous Credit Constraints, Human Capital Investment And Optimal Tax Policy

    This paper employs a two-period life-cycle model to derive the optimal tax policy when educational investments are subject to credit constraints. Credit constraints arise from the limited commitment of debtors to repay loans and are endogenously determined by private banks under the non-default condition that individuals cannot be better off...

    Provided By University of Konstanz

  • White Papers // Dec 2011

    CTL: A Platform-Independent Crypto Tools Library Based on Dataflow Programming Paradigm

    The diversity of computing platforms is increasing rapidly. In order to allow security applications to run on such diverse platforms, implementing and optimizing the same cryptographic primitives for multiple target platforms and heterogeneous systems can result in high costs. In this paper, the authors report their efforts in developing and...

    Provided By University of Konstanz

  • White Papers // May 2012

    Causality Checking for Complex System Models

    The authors present an approach for the algorithmic computation of causalities in system models that they refer to as causality checking. They are basing their notion of causality on counterfactual reasoning, in particular using the structural equation model approach proposed in that has been extended to reasoning about computational models...

    Provided By University of Konstanz