Thomas Klotz

Automatic generation of complex properties for hardware designs

Property checking is a promising approach to prove the correctness of todays complex designs. However, in practice this requires the formulation of formal properties which is a time consuming and non-trivial task. Therefore the acceptance and efficiency of formal verification techniques can be raised by an automated support for formulating design properties. In this paper we propose a new methodology to automatically generate complex properties for a given design. The tool, Dianosis, implements this methodology by analyzing a simulation trace. The extracted properties describe the abstract design behavior and are presented in a format that is easy to read and can be added to the set of properties used for formal or assertion-based verification. We provide experimental results on industrial hardware designs that show the effectiveness of Dianosis and motivate the practical use.

Formal verification of UML-modeled machine controls

Programmable logic controllers (PLCs) are applied in a wide field of application and, especially, for safety-critical controls. Thus, there is the demand for high reliability of PLCs. Moreover, the increasing complexity of the PLC programs and the short time-to-market are hard to cope with. Formal verification techniques such as model checking allow for proving whether a PLC program meets its specification. However, the manual formalization of PLC programs is error-prone and time-consuming. This paper presents a novel approach to apply model checking to machine controls. The PLC program is modeled in form of Unified Modeling Language (UML) state-charts that serve as the input to our tool that automatically generates a corresponding formal model for the model checker NuSMV. We evaluate the capabilities of the proposed approach on an industrial machine control.

An approach to the verification of material handling systems

The development of correctly working logistic systems is a tedious task. On the one hand, the developer is faced with the increasing complexity of systems and shrinking time-to-markets, but on the other hand, the need for reliability and safety of the implemented controls becomes more and more important. Formal verification techniques such as model checking allow for proving whether a system completely fulfills its specification. Existing work, though, considered only the verification of single controllers, but did not analyze the behavior of a complete logistic system. In this paper, an approach to the formal verification of material handling systems is presented. The approach is based on the definition of material handling system elements and their interconnection. Experimental results show that the approach can ensure the correct functionality of logistic systems.

Modelling the real-time behaviour of machine controls using UML statecharts

For covering the real-time characteristics of an automation system during model-based design it is essential to model not only the function but also the behaviour of the control programs running on a real-time controller. This paper introduces an approach to the modelling and evaluation of the functional and time behaviour of Programmable Logic Controllers (PLC) on model level. The control algorithm consisting of UML statecharts is extended with an execution model of the controller which is also given as a statechart. The approach is integrated into a model-based design system for industrial control systems focusing on the field of production systems. An example will be employed to illustrate the benefits of a model-based design system which does incorporate real-time aspects of the controller.

Compositional verification of material handling systems

The design of properly working material handling systems (MHS) is a difficult process as these systems consist of a vast number of single elements with dedicated controls. While currently these systems are usually validated using simulation, formal methods provide a means to analyze the complete behavior of a system. However, these methods can often only be applied to systems of a moderate size, which hampers their application to verify real-world systems. This paper presents an approach to the compositional verification of MHS, which is based on the theory of assume-guarantee reasoning. The approach has been implemented in a tool that automatically carries out the verification. The application of the approach is shown using a real-world example.

On the formal verification of routing in material handling systems

The correct design of complex material handling systems (MHS) is a challenging task, mainly because of short development cycles and ever increasing system sizes. For baggage handling systems (BHS) at airports, the correct design of routing strategies is of special importance, as these strategies are non-trivial but safety-critical. This paper presents a novel approach to prove the correctness of routing in MHS. The approach is based on assume-guarantee reasoning which allows to derive proofs of the overall system using a divide and conquer strategy. The proposed approach is automated and has been implemented in a tool. The application of the approach is shown using a real-world BHS.

Toward verification of material handling systems

The correct designing of todays logistic systems has become an increasingly cumbersome process, especially due to their growing sizes and heterogeneities. While simulation methods provide a means to validate the functional behavior of logistic systems, formal methods allow for proving that the system completely fulfills its specification. This paper presents a novel approach to the formal verification of material handling systems, which is based on setting up material handling system elements that are proven to be correct. The application of the approach is shown using an illustrative example.

Reliable execution of statechart-generated correct embedded software under soft errors

This paper proposes a design methodology for fault-tolerant embedded systems development that starts from software specification and goes down to hardware execution. The proposed design methodology uses formally verified and correct-by-construction software created from high-level UML statechart models for software specification and implementation. On the hardware reliability side, this paper uses the MoMa architecture for reliable embedded computing which we deploy as a soft-core onto an off-the-shelf FPGA. MoMa introduces architectural innovations that support the semantics of the UML statechart execution in a reliable fashion. The proposed design methodology is evaluated with a real automotive case study based on an exhaustive FPGA-implemented fault injection campaign.

Model checking specifications of smart cards

Formally verifying a product in an early phase of the design process has several advantages. First, errors and contradictions in the specification can be found early. Second, an unambiguous common understanding of the specification is created. In summary, the quality and security of a product can be significantly increased. This paper describes how formal verification can be integrated into the industrial design process of a smart card in a practical way. The described method allows to reach high assurance levels in Common Criteria certifications.

Automated Formal Verification of Routing in Material Handling Systems

The design of correctly implemented controls in material handling systems (MHS) is time consuming and cumbersome. The developer has to deal with an ever increasing complexity and heterogeneity of MHS on the one hand, but also with short development cycles and high demands to MHS on the other hand. For baggage handling systems (BHS) at airports, the error-free implementation of routing strategies is especially of importance, as these strategies are critical to safety. This paper proposes a compositional approach to the formal verification of routing in MHS. The approach is based on the theory of assume-guarantee reasoning, where proofs of the overall system are derived from proofs of subsystems. Moreover, the approach has been implemented in a tool that automatically carries out the verification. A real-world example is discussed in this paper, showing the benefits and scalability of the presented approach.