From Scenarios to Optimally Allocated Timed Automata

University of Minnesota M.S. thesis. June 2017. Major: Computer Science. Advisor: Neda Saeedloei. 1 computer file (PDF); vi, 62 pages.Our contribution is twofold. First, we develop a new method for synthesizing a formal model for real-time systems from scenarios. Scenarios describe partial behaviours of realtime systems during some time interval. We propose Timed Event Sequences to formally express scenarios. Given a set of scenarios as Timed Event Sequences, along with a mode graph, we propose a method to automatically construct a minimal, acyclic, and deterministic timed automaton that models the specified aspects of the system. Second, we consider the problem of optimally allocating clocks in timed automata. Reducing the number of clocks in a timed automaton is important, as it directly affects the complexity of the verification problem. Given a timed automaton, it is undecidable, in general, to check whether there exists another timed automaton that accepts the same language but has fewer number of clocks. We identify a fairly general class of timed automata and propose an algorithm (polynomial time) for optimally allocating clocks to timed automata in this class. The previous approaches changed the shape of the graph of the original timed automaton by constructing bisimilar timed automata. Our method does not change the graph of timed automata. The cost of our algorithm is quadratic in the size of the underlying graph of the timed automaton

Nobody’s perfect: interactive synthesis from parametrized real-time scenarios

ABSTRACT As technical systems keep growing more complex and sophisticated, designing software for the safety-critical coordination between their components becomes increasingly difficult. Verifying and correcting these components already represents a significant part of the development process both with respect to time and cost. Scenario-based synthesis has been put forward as an approach to accelerate the transition from requirements to a correct, verified model. I

Aspects of Availability Enforcing timed properties to prevent denial of service

We propose a domain-specific aspect language to prevent denial of service caused by resource management. Our aspects specify availability policies by enforcing time limits in the allocation of resources. In our language, aspects can be seen as formal timed properties on execution traces. Programs and aspects are specified as timed automata and the weaving process as an automata product. The benefit of this formal approach is two-fold: the user keeps the semantic impact of weaving under control and (s)he can use a model-checker to optimize the woven program and verify availability properties

Automatic synthesis of SDL from MSC and its applications in forward and reverse engineering

Abstract Wider adoption of formal specification languages in industry is impeded by the lack of support for early development phases and for integration with older, legacy software. Methodology aimed at improving this situation is presented. The methodology uses Message Sequence Charts (MSC) as a "front-end" specification language and systematically applies an automatic synthesis technique to produce executable specifications in the telecommunications standard Specification and Description Language (SDL). Applications of the automatic synthesis technique for both forward and reverse engineering are demonstrated

Increasing the Semantic Similarity of Object-Oriented Domain Models by Performing Behavioral Analysis First

The main goal of any object-oriented analysis (OOA) method is to produce a model that aids in understanding and communicating knowledge about a modeled domain. A higher degree of similarity among independently produced domain models provides an indication of how well the domain was understood by the different analysts, i. e. , more similar models indicate a closer and a more common understanding of a domain. A common understanding is of critical importance for effective knowledge communication and sharing. The core of any OOA method is discovering and understanding concepts and their relationships in a domain. The main artifact produced by an OOA method is a domain model of the domain. A domain model often serves as the main source of design concepts during objectoriented design (OOD). This thesis evaluates two OOA methods by comparing the degree of similarity of the resulting domain models. In particular, this work compares the semantic similarity of domain models extracted from use cases by specification of sequence diagrams and then domain models, and specification of unified use case statecharts and then domain models. The thesis makes case studies out of the application of the first method to 31 instances of large Voice-over-IP (VoIP) system and its information management system (IMS) and to 3 small elevator systems, and out of the application of the second method to 46 instances of the same large VoIP system and its IMS and to 12 instances of a medium-sized elevator system. From an analysis of data from these case studies, the thesis concludes that there is an increase of 10% in the semantic similarity of domain models produced using the second method, but at the cost of less than or equal to 25% more analysis time

From Scenarios to Timed Automata: Building Specifications from Users Requirements

Scenarios as partial behavior descriptions, are used more and more to represent users requirements, and to conduct software engineering. This paper examines automatic generation of specifications from requirements. This is a crucial step when accuracy is desired in the requirement engineering process. Automatic construction of specifications from scenarios reduces to the merging of partial behaviors into global specifications, such that these specifications can reproduce them. This paper presents an incremental algorithm that synthesizes timed automata from scenarios with timing constraints. The algorithm is based on a formalism developed for scenarios. Its uses operations semantics, and a mapping between concepts of scenarios, and those of the theory of timed automata. Keywords: Requirements Engineering, Scenarios, Timed automata, Synthesis, Timing constraints. 1 Introduction A scenario is a partial behavior description of the interaction between a system and its environment in a re..