Gábor Huszerl

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.

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.

Modeling and analysis of redundancy management in distributed object-oriented systems by using UML statecharts

The paper presents techniques that enable the modeling and analysis of redundancy schemes in distributed object-oriented systems. The replication manager, as a core part of the redundancy scheme, is modeled by using UML statecharts. The flexibility of the statechart-based modeling, which includes event processing and state hierarchy, enables an easy and efficient modeling of replication strategies as well as repair and recovery policies. The statechart is transformed to a Petri-net based dependability model, which also incorporates the models of the replicated objects. By the analysis of the Petri-net model the designer can obtain reliability and availability measures that can be used in the early phases of the design to compare alternatives and find dependability bottlenecks. Our approach is illustrated by an example.

Towards Dependability Modeling of FT-CORBA Architectures

The paper presents techniques to support the dependability modeling and analysis of distributed object-oriented applications that are designed according to the Fault Tolerant CORBA (FT-CORBA) specification. First the construction of a high-level dependability model is described. It is based on the architecture of the application and allows the analysis of the fault tolerance strategies and properties that are directly supported by the standard infrastructure. Then a technique to construct a refined dependability model is presented. It exploits the detailed behavioral model of the object responsible for replica maintenance. The UML statechart of this object is transformed to a stochastic Petri net that forms the core of the dependability model. In this way the designer is allowed to utilize the full power of statecharts to construct models of application-dependent replication strategies and recovery policies.