206854015
Fitness Distance Correlation and Ridge Functions
Fitness Distance Correlation has been proposed as a measure of function optimization difficulty. This paper describes a class of functions, named the Ridge Functions which, according to the measure, should be highly misleading. However, all functions tested were optimized easily by both a GA and a simple hill climbing algorithm. Scatter graph analysis of Ridge functions gave little guidance due to the large number of functions with an identical scatter graph, the majority of which are not in the class of Ridge functions and are not simple to optimize.
42279258
A Unified Paradigm for Parallel Genetic Algorithms
Genetic Algorithms contain natural parallelism. There are two main approaches in parallelising GAs. The first one is parallelising individual functional components of a standard, sequential GA. The only difference with the sequential GA is in the computation speed. The second approach more closely resembles the real life simultaneous evolution of species, which is the central theme in GAs. Algorithms following this approach are still referred to as GAs but are different from Holland's standard GA. For these algorithms it is not the improvement in computation speed that is the driving factor, but the efficiency with which they search a given solution space. We describe a number of the most common parallel GA methods found in the literature and mention practical issues concerning their implementation in a Transputer based system. We go on to introduce the Unified Parallel GA system, based on our GA toolkit, GAmeter, which allows the user to select one or more of the GA methods described, by setting various parameters. Finally we present results for the Steiner tree Problem in Graphs (SPG).
6921917
Recursive Schema Definitions in Object-Z
Unlike Z, Object-Z allows schemas to be defined recursively. This enables mutual and self recursive structures, commonly occurring in object-oriented programs, to be readily specified. In this paper, we provide a fixed point interpretation of such definitions. In addition, we provide simple guidelines for producing non-recursive schema definitions which are semantically identical to recursive ones.
16885662
Proving Temporal Properties of Z Specifications Using Abstraction
This paper presents a systematic approach to proving temporal properties of arbitrary Z specifications. The approach involves (i) transforming the Z specification to an abstract temporal structure (or state transition system), (ii) applying a model checker to the temporal structure, (iii) determining whether the temporal structure is too based on the model checking result and (iv) refining the temporal structure where necessary. The approach is based on existing work from the model checking literature, adapting it to Z.
8809836
Model Checking Z Specifications Using SAL
The Symbolic Analysis Laboratory (SAL) is a suite of tools for analysis of state transition systems. Tools supported include a simulator and four temporal logic model checkers. The common input language to these tools was originally developed with translation from other languages, both programming and specification languages, in mind. It is, therefore, a rich language supporting a range of type definitions and expressions. In this paper, we investigate the translation of Z specifications into the SAL language as a means of providing model checking support for Z. This is facilitated by a library of SAL definitions encoding the Z mathematical toolkit.
9661135
Reasoning about Object-Z specifications
This paper presents a method of reasoning about Object-Z specifications. The approach utilises the modularity inherent in Object-Z specifications to simplify proofs. Properties proved for a class in isolation can be used when that class is either inherited by another class or instantiated as part of a system of interacting objects. Proofs using structural induction and the notion of object integrity are discussed.
30219210
Compositional Class Refinement in Object-Z
Object-Z allows coupling constraints between classes which, on the one hand, facilitate specification at a high level of abstraction, but, on the other hand, make class refinement non-compositional. The consequence of this is that refinement is not practical for large systems. This paper overcomes this limitation by introducing a methodology for compositional class refinement in Object-Z. The key step is an equivalence transformation of an arbitrary Object-Z specification to one in which introduced constraints prohibit non-compositional refinements. The methodology also allows the constraints which couple classes to be refined yielding an unrestricted approach to compositional class refinement.