Formal Verification of Object-Oriented Graph Grammars Specifications

Attractive round-up of a complex area: Design and Validation of Computer Protocolsby Gerard J Holzman. Published by Prentice Hall, 1992, £22.95, 500 pp

This article describes first steps towards the formal specification and verification of multi-agent systems, through the use of temporal belief logics. The article first describes Concurrent METATEM, a multi-agent programming language, and then develops a logic that may be used to reason about Concurrent METATEM systems. The utility of this logic for specifying and verifying Concurrent METATEM systems is demonstrated through a number of examples. The article concludes with a brief discussion on the wider implications of the work, and in particular on the use of similar logics for reasoning about multi-agent systems in general.

In Full Maude, concurrent object-oriented systems can be defined by means of object-oriented modules—introduced by the keyword omod...endom—using a syntax more convenient than that of system modules, because it assumes acquaintance with the basic entities, such as objects, messages and configurations, and supports linguistic distinctions appropriate for the object-oriented case.

Representation of scopes of names is important for analysis and verification of concurrent systems. However, it is difficult to represent the scopes of channel names precisely with models based on process algebra.We introduced a model of concurrent systems with higher-order communication based on graph rewriting in our previous work. A bipartite directed acyclic graph represents a concurrent system that consists of a number of processes and messages in that model. The model can represent the scopes of local names precisely. We defined an equivalence relation such that two systems are equivalent not only in their behavior, but also in extrusion of scopes of names. This paper shows that our equivalence relation is a congruence relation w.r.t. τ-prefix, new-name, replication and composition, even when higher-order communication is allowed. We also show our equivalence relation is not congruent w.r.t. input-prefix though it is congruent w.r.t. input-prefix in the first-order case.

Concurrent object-oriented programming systems require support for concurrency control, to enforce consistent commitment of changes and to support program-initiated rollback after application-specific failures. We have explored three different concurrency control models atomic blocks, serializable transactions, and commit-serializable transactions - as part of the MELD programming language. We present our designs, discuss certain programming problems and implementation issues, and compare our work on MELD to other concurrent object-based systems.

Translating Controlled Graph Grammars to Ordinary Graph Grammars

Graph Grammars are a visual formal language for which there are several techniques of system specification and verification. This fact makes them an attractive option for describing complex systems. Fuzzy graph grammars generalize the concept of graph grammars, using fuzzy graphs. A fuzzy graph is composed of vertices and edges that have an associated membership value, which varies within a range of 0 to 1. Due to the lack of technique and analysis tools for fuzzy graph grammars, their use is still quite limited. One way to allow the analysis of fuzzy graphs grammars is using the extension of existing graph grammar approaches, including the concept of membership in the graph components. There is a relational approach of graph grammars that allows the use of theorem provers to perform property analysis of systems described in this language. This approach is the basis of a translation of graph grammars into the Event-B language, which enables the use of theorem provers of the Rodin tool. Therefore, the aim of this work is to extend this graph grammar approach, including fuzzy concepts, to allow the use of the theorem proving technique to analyze fuzzy graph grammars. In order to set this extension was first necessary to define the notion of typed fuzzy graph grammars.

Narrowing and heuristic search for symbolic reachability analysis of concurrent object-oriented systems

Firstly, net theory, which is a well established theory of distributed systems and processes [I] relies heavily on a graphical notation. One of the strengths of this theory is that many of the fundamental notions concerning concurrent systems and in particular, the dynamics of a concurrent systemcan be made transparent with the help of simple net diagrams and transformations of such diagrams. It is important to provide a solid formal foundation to this aspect of net theory and graph grammars appear to be the obvious tool for doing so. The second motivation is that in the study of concurrency problems that arise within the area of graph grammars [2] we think it is possible and fruitful to apply the concepts and techniques of net theory.

Graph transformation has recently become more and more popular as a general, rule-based visual specification paradigm to formally capture (a) requirements or behavior of user models (on the model-level), and (b) the operational semantics of modeling languages (on the meta-level) as demonstrated by benchmark applications around the Unified Modeling Language (UML). The current paper focuses on the model checking-based automated formal verification of graph transformation systems used either on the model-level or meta-level. We present a general translation that inputs (i) a metamodel of an arbitrary visual modeling language, (ii) a set of graph transformation rules that defines a formal operational semantics for the language, and (iii) an arbitrary well-formed model instance of the language and generates a transitions system (TS) that serve as the underlying mathematical specification formalism of various model checker tools. The main theoretical benefit of our approach is an optimization technique that projects only the dynamic parts of the graph transformation system into the target transition system, which results in a drastical reduction in the state space. The main practical benefit is the use of existing back-end model checker tools, which directly provides formal verification facilities (without additional efforts required to implement an analysis tool) for many practical applications captured in a very high-level visual notation. The practical feasibility of the approach is demonstrated by modeling and analyzing the well-known verification benchmark of dining philosophers both on the model and meta-level.

A concurrent object-oriented programming language system for highly parallel data-driven computers and its applications

Model checking is one of the successful techniques in automated verification of software and hardware systems. However, employing this technique for verification of properties such as the safety and liveness requires that all possible states of a system are generated and then the given property is checked. In large and complex systems, generating all states causes the state space explosion problem. Hence, it is possible to refute such properties by searching the state space to find a state in which the given property is violated. Of course, it is possible that detecting such states in complex systems leads to the exhaustive exploration of the state space. Recent researches confirm that using meta-heuristic and evolutionary approaches to intelligently explore a portion of the state space can be a promising idea. Hence, in this paper, we propose an approach based on ant colony optimization algorithm for refuting the safety and liveness properties and also analyzing reachability ones in systems specified formally through graph transformation system. Refutation of liveness and analyzing reachability properties in systems modeled by graph transformations are the prominent advantages of this approach in comparison with the previous approaches. The proposed approach is implemented in GROOVE which is an open source toolset for designing and model checking graph transformation systems. Experimental results show that our proposed approach is faster and it generates shorter counterexamples in comparison with others.

Using graph transformation as a formalism to specify access control has several advantages, from the intuition provided by the visual aspect to the precise semantics and the systematic verification of constraints. Graph Transformations provide a uniform and precise framework for the specification of access control policies. After reviewing the basic notations of graph transformation, this article presents specification formalisms for workflow delegation policies using graph transformation. The authorization states are represented by graphs and state transition by graph transformation. The proposed formalization provides an intuitive description for the manipulation of graph structures as they occur in workflow delegation and a precise specification of consistency conditions on graphs and graph transformations. We specifies a type graph to represents the type information in the graph transformation for workflow delegation, a set of rules to build the system states and sets of positive and negative constraints to specify wanted and unwanted framework.

The complexity of designing concurrent and highly-evolving interactive systems has grown to a point where system verification has become a hurdle. Fortunately, formal verification methods have arrived at the right time. They detect errors, inconsistencies and incompleteness at early development stages of a system formally modeled using a formal specification language. -calculus (Milner, 1999) is one such formal language which provides strong mathematical base that can be used for verifying system specifications. But manually verifying the specifications of concurrent systems is a very tedious and error-prone work, especially if the specifications are large. Consequently, an automated verification tool would be essential for efficient system design and development. In addition, formal verification tools are vital ingredient to fully harness the potential of component-based software composition. The authors developed such an automated verification tool which is highly portable and seamlessly integrates with the visualization, reduction and performance evaluation tools introduced (Ahmad & Rahimi, 2008; Rahimi, 2006; Rahimi et al., 2001, 2008) to provide a comprehensive tool for designing and analyzing multi process/agent systems. Open-Bisimulation (Sangiorgi, 1996) concept is utilized as the theoretical base for the design and implementation of the tool which incorporates an expert system implemented in Java Expert System Shell (JESS) (Friedman-Hill, 2003).

High quality software components require a representation that allows the implementation-independent description of the structure and behavior of software components. Hence, the static as well as the dynamic structure of the system has to be represented in a structured way. Graph transformation systems support static and dynamic modeling through a single computational framework for the sake of correctness, maintainability, and integrity. The framework introduced along with the corresponding tool, UPGraDE (Universal Programmed Graph Grammar Development Environment), which is based on the universal graph language GRASP (GRAph grammar with Set Productions). Any type of system can be specified through a minimal set of operations (syntax) and rules to specify the behavior of any type of software (semantics). The UPGraDE Environment, consisting of several totally transparent interconnected modules, performing well defined tasks, is a highly modular and extensible environment suited for nearly every GRASP development purpose.