András Pataricza

VIATRA - visual automated transformations for formal verification and validation of UML models

The VIATRA (visual automated model transformations) framework is the core of a transformation-based verification and validation environment for improving the quality of systems designed using the Unified Modeling Language by automatically checking consistency, completeness, and dependability requirements. In the current paper, we present an overview of (i) the major design goals and decisions, (ii) the underlying formal methodology based on metamodeling and graph transformation, (iii) the software architecture based upon the XMI standard, and (iv) several benchmark applications of the VIATRA framework.

Designing the automatic transformation of visual languages

The design process of complex systems requires a precise checking of the functional and dependability attributes of the target design. The growing complexity of systems necessitates the use of formal methods, as the exhaustiveness of checks performed by the traditional simulation and testing is insufficient.For this reason, the mathematical models of various formal verification tools are automatically derived from UML-diagrams of the model by mathematical transformations guaranteeing a complete consistency between the target design and the models of verification and validation tools.In the current paper, a general framework for an automated model transformation system is presented. The method starts from a uniform visual description and a formal proof concept of the particular transformations by integrating the powerful computational paradigm of graph transformation, planner algorithms of artificial intelligence, and various concepts of computer engineering.

Generic and Meta-transformations for Model Transformation Engineering

The Model Driven Architecture necessitates not only the application of software engineering disciplines to the specification of modeling languages (language-ware) but also to design inter and intra-language model transformations (transformation-ware). Although many model transformation approaches exist, their focus is almost exclusively put on functional correctness and intuitive description language while the importance of engineering issues such as reusability, maintainability, performance or compactness are neglected. To tackle these problems following the MDA philosophy, we argue in the paper that model transformations should also be regarded as models (i.e., as data). More specifically, we demonstrate (i) how generic transformations can provide a very compact description of certain transformation problems and (ii) how meta-transformations can be designed that yield efficient transformations as their output model.

VPM: A visual, precise and multilevel metamodeling framework for describing mathematical domains and UML (The Mathematics of Metamodeling is Metamodeling Mathematics)

As UML 2.0 is evolving into a family of languages with individually specified semantics, there is an increasing need for automated and provenly correct model transformations that (i) assure the integration of local views (different diagrams) of the system into a consistent global view, and, (ii) provide a well-founded mapping from UML models to different semantic domains (Petri nets, Kripke automaton, process algebras, etc.) for formal analysis purposes as foreseen, for instance, in submissions for the OMG RFP for Schedulability, Performance and Time. However, such transformations into different semantic domains typically require the deep understanding of the underlying mathematics, which hinders the use of formal specification techniques in industrial applications. In the paper, we propose a multilevel metamodeling technique with precise static and dynamic semantics (based on a refinement calculus and graph transformation) where the structure and operational semantics of mathematical models can be defined in a UML notation without cumbersome mathematical formulae.

Stochastic dependability analysis of system architecture based on UML models

The work in this paper is devoted to the definition of a dependability modeling and model based evaluation approach based on UML models. It is to be used in the early phases of the system design to capture system dependability attributes like reliability and availabiUty, thus providing guidelines for the choice among different architectural and design solutions. We show how structural UML diagrams can be processed to filter out the dependability related information and how a system-wide dependability model is constructed. Due to the modular construction, this model can be refined later as more detailed information becomes available. We discuss the model refinement based on the General Resource Model, an extension of UML. We show that the dependability model can be constructed automatically by using graph transformation techniques.

Quantitative Analysis of UML Statechart Models of Dependable Systems

The paper introduces a method which allows quantitative dependability analysis of systems modeled by using the Unified Modeling Language (UML) statechart diagrams. The analysis is performed by transforming the UML model to stochastic reward nets (SRNs). A large subset of statechart model elements is supported including event processing, state hierarchy and transition priorities. The transformation is presented by a set of SRN patterns. Performance-related measures can be directly derived using SRN tools, while dependability analysis requires explicit modeling of erroneous states and faulty behavior.

Towards Testing the Implementation of Graph Transformations

We present a method for testing the implementation of graph transformation specifications focusing on test case generation for graph pattern matching. We propose an extensible fault model for the implementation of transformations based on common programmer faults and the technicalities of graph transformations. We integrate traditional hardware testing (combinational circuits) and software testing techniques (mutant generation) for generating test cases.

Checking General Safety Criteria on UML Statecharts

This paper describes methods and tools for automated safety analysis of UML statechart specifications. The general safety criteria described in the literature are reviewed and automated analysis techniques are proposed. The techniques based on OCL expressions and graph transformations are detailed and their limitations are discussed. To speed up the checker methods, a reduced form for UML statecharts is introduced. Using this form, the correctness and completeness of some checker methods can be proven. An example illustrates the application of the tools developed so far.

Metamodeling Mathematics: A Precise and Visual Framework for Describing Semantics Domains of UML Models

As UML 2.0 is evolving into a family of languages with individually specified semantics, there is an increasing need for automated and provenly correct model transformations that (i) assure the integration of local views (different diagrams) of the system into a consistent global view, and, (ii) provide a well-founded mapping from UML models to different semantic domains (Petri nets, Kripke automaton, process algebras, etc.) for formal analysis purposes as foreseen, for instance, in submissions for the OMG RFP for Schedulability, Performance and Time. However, such transformations into different semantic domains typically require the deep understanding of the underlying mathematics, which hinders the use of formal specification techniques in industrial applications. In the paper, we propose a UML-based metamodeling technique with precise static and dynamic semantics (based on a refinement calculus and graph transformation) where the structure and operational semantics of mathematical models can be defined in a UML notation without cumbersome mathematical formulae.

Watchdog processors in parallel systems

Abstract A watchdog processor (WDP) is a relatively simple coprocessor built for concurrent, information compaction based error detection in the main program control flow. A new algorithm called SEIS (Signature Encoded Instruction Stream) is presented for assigning signatures to high level-instructions. The main idea of this method is to embed the information necessary to the program flow check into the signatures themselves, thus avoiding large reference databases in the WDP and allowing high operational speed. Solutions for a fault-tolerant multiprocessing and multi-tasking implementation are described as well.