SYSTEM THEORETIC FORMALISMS FOR COMBINED DISCRETE-CONTINUOUS SYSTEM SIMULATION

In this paper we present an approach to combined discrete-continuous modelling which can be used to model and simulate an intelligent multi-layer control architecture as can be found in high autonomy systems. The modelling approach is based on system theoretical concepts; the three system specification formalisms-differential equation, discrete time, and the discrete event system specification formalism-have been combined to facilitate multi-formalisms modelling. Simulation concepts are based on the abstract simulator concept for discrete event simulation developed by Zeigler. Similar simulation methods have been developed to simulate modular, hierarchical discrete time and differential equation specified systems as well as multi-formalism models. Included in the paper are several examples of multi-formalism models together with the simulation results from the STIMS environment-an implementation of the modelling and simulation concepts in Interlisp-D/LOOPS.     

Specification and Verification of Communication Protocols in AFFIRM Using State Transition Models

It is becoming increasingly important that communication protocols be formally specified and verified. This paper describes a particular approach–the state transition model–using a collection of mechanically supported specification and verification tools incorporated in a running system called AFFIRM. Although developed for the specification of abstract data types and the verification of their properties, the formalism embodied in AFFIRM can also express the concepts underlying state transition machines. Such models easily express most of the events occurring in protocol systems, including those of the users, their agent processes, and the communication channels. The paper reviews the basic concepts of state transition models and the AFFIRM formalism and methodology and describes their union. A detailed example, the alternating bit protocol, illustrates varous properties of interest for specification and verification. Other examples explored using this formalism are briefly described and the accumulated experience is discussed.     

Implementing associations: UML 2.0 to Java 5

A significant current software engineering problem is the conceptual mismatch between the abstract concept of an association as found in modelling languages such as UML and the lower level expressive facilities available in object-oriented languages such as Java. This paper introduces some code generation patterns that aid the production of Java based implementations from UML models. The work is motivated by a project to construct model driven development tools in support of the construction of embedded systems. This involves the specification and implementation of a number of meta-models (or models of languages). Many current UML oriented tools provide code generation facilities, in particular the generation of object-oriented code from class diagrams. However, many of the more complex aspects of class diagrams, such as qualified associations are not supported. In addition, several concepts introduced in UML version 2.0 are also not supported.The aim of the work presented in this paper is to develop a number of code generation patterns that allow us to support the automatic generation of Java code from UML class diagrams that support these new and complex association concepts. These patterns significantly improve the code generation abilities of UML tools, providing a useful automation facility that bridges the gap between the concept of an association and lower level object-oriented programming languages.     

Linguistic extension of abstract machine modelling to aid software development

The traditional use of abstract machine models is to provide a conceptual framework for software design and to aid portability and machine independence. Access to the abstract machine model from the higher-level system on which it is based provides a powerful tool for software development. This paper describes a technique in which the higher-level system is interfaced to the underlying abstract machine, thus allowing use of the higher-level system to analyse and debug its own implementation. The application of this technique in the implementation of SL5 is given as an example. Experience with the use of the facility and a discussion of basic design considerations are included.     

A generic model for software architectures

In other industries, the idea of build corporate culture by establishing a common level of “best practice” is widely known and used. The architecture concept directly supports this goal for our industry and can help us improve problem areas dominated by organizational and social issues, such as health care organizations, educational systems, and so on. Our proposed reference model for architecture specification and development is organized around a set of aspects that structure concepts and rules; these, in turn, specify a conceptual architecture. We have added principles and guidelines to the concepts and rules to give a more complete picture of the architecture and to provide a place to store and communicate successfully applied design patterns and other knowledge related to the architecture. Adding architectural elements is a step toward a more constructive type of architecture representation. Our current research is focused on further refining these concepts and developing a formal specification of the architecture reference model. We are continuing to test our ideas in case studies, such as applying our model to the OSCA architecture and the application machine concept. We are also developing a prototype architecture editor, and we are testing different tools to learn more about integrating them into a real infrastructure and to learn what typical services an infrastructure must provide     

Visual knowledge specification for conceptual design: Definition and tool support

Current CAD tools are not able to support the conceptual design phase, and none of them provides a consistency analysis for sketches produced by architects. This phase is fundamental and crucial for the whole design and construction process of a building. To give architects a better support, we developed a CAD tool for conceptual design and a knowledge specification tool. The knowledge is specific to one class of buildings and it can be reused. Based on a dynamic and domain-specific knowledge ontology, different types of design rules formalize this knowledge in a graph-based form. An expressive visual language provides a user-friendly, human readable representation. Finally, a consistency analysis tool enables conceptual designs to be checked against this formal conceptual knowledge.In this article, we concentrate on the knowledge specification part. For that, we introduce the concepts and usage of a novel visual language and describe its semantics. To demonstrate the usability of our approach, two graph-based visual tools for knowledge specification and conceptual design are explained.     

Calculating upward and downward simulations of state-based specifications

This paper concerns calculational methods of refinement in state-based specification languages. Data refinement is a well-established technique for transforming specifications of abstract data types into ones, which are closer to an eventual implementation. The conditions under which a transformation is a correct refinement are encapsulated into two simulation rules: downward and upward simulations.One approach for refining an abstract system is to specify the concrete data type, and then attempt to verify that it is a valid refinement of the abstract type. An alternative approach is to calculate the concrete specification based upon the abstract specification and a retrieve relation, which links the abstract and concrete states. In this paper we generalise existing calculational methods for downward simulations and derive similar results for upward simulations; we also document their use and application in a particular specification language, namely Z.     

View Transformation in Visual Environments applied to Algebraic High-Level Nets

Graph transformation systems are a well-founded and adequate technique to describe the syntax of visual modeling languages and to formalize their semantics. Moreover, graph transformation tools support visual model specification, simulation and analysis on the basis of the rich underlying theory.Despite the benefits of model validation by simulation, sometimes it is preferable for users to see the model's behavior not in the abstract layout of the formal model, but as scenarios presented in the layout of the specific application domain. Hence, we propose the integration of a domain-oriented animation view with the model transformation system. An animation view allows to define scenario animations in a systematic way based on the formal model. The specification of the well-known Dining Philosophers system as algebraic high-level Petri net serves as running example for the extension of the model by an animation view and the derivation of animation rules from the model transformation system. A scenario animation then is obtained as transformation by applying the animation rules to model states. This visualizes the behavior of the model in the layout of philosophers sitting around a table and eating with chopsticks. A prototypical implementation of the concepts in GenGED, a visual language environment, is presented.     

A portable diagnostic facility for SNOBOL4

In programming systems based on abstract machine modelling concepts, the underlying structure of the abstract machine can be made available to the software implemented on it. The result is an unusual facility for diagnosis and exploration of software structure. Such a facility has been added to the macro implemention of SNOBOL4. This paper describes the nature of the facility, illustrates its use, and presents some results of using it for language implementation and development.     

ODP enterprise viewpoint specification

The Open Distributed Processing (ODP) standardisation initiative has led to a framework by which distributed systems can be modelled using a number of viewpoints. These include an enterprise viewpoint, which focuses on the objectives and policies of the enterprise that the system is meant to support. Although the ODP reference model provides abstract languages of relevant concepts, it does not prescribe particular techniques that are to be used in the individual viewpoints. In particular, there is a need to develop appropriate notations for ODP enterprise specification, in order to increase the applicability of the ODP framework. In this paper, we tackle this concern and develop a specification language to support the current draft of the enterprise viewpoint. In doing so, we analyse the current definition of the ODP enterprise viewpoint language. Using the Unified Modelling Language (uml), a meta-model of the core concepts and their relationships is constructed, and we also investigate to what extent the uml can be used for enterprise viewpoint specification. We, then, focus on the expression of enterprise policies that govern the behaviour of enterprise objects. We develop a policy language, which is a combination of structured English and simple predicate logic and is built on top of the formal object-oriented specification language Object-Z, into which the complete language is translated. We illustrate the ideas in the paper with a case study that presents an enterprise specification of a library support system.     

代数规范描述及其语义的研究

用代数规范描述来描述抽象数据类型的基本思想是用它的标记和特征性质来说明抽象数据类型,它们的性质可用多类逻辑形式来表示,通常为受限的一价逻辑,例如等式     

基于混合功能推理的机械系统概念设计的研究

给出了产品设计说明形式化的描述,应用P/T网对原型机构抽象结构进行表示,利用编码技术对功能要求、功能约束及结构约束进行编码,建立了原型机构知识库。在所提出的基于设计说明和问题解重定义的正、反向混合推理方法的基础上,采用功能相似性度量的控制策略,进行复杂机械系统的概念设计,完成整个概念空间的构建。最后用实例对推理过程的自动性及方法的有效性进行了验证。     

Modelling a Society of Simple Agents: From Conceptual Specification to Experimentation

Much research concerning the design of multi-agent systems (at a conceptual level) addresses complex agents that exhibit complex interaction patterns. Due to this complexity, it is difficult to perform rigorous experimentation. On the other hand, systematic experimental work regarding behaviour of societies of more simple agents, while reporting valuable results, often lacks conceptual specification of the system under consideration. In this paper, the compositional multi-agent modelling framework DESIRE is not only successfully used to develop a conceptual specification of the simple agents discussed by A. Cesta, M. Miceli and P. Rizzo (Lecture Notes in Artificial Intelligence, vol. 1038, Springer-Verlag: Berlin, pp. 128–138, 1996), but also to simulate the behaviour in a dynamical environment. In the DESIRE framework, a conceptual specification, which provides a high-level view of an agent, has enough detail for automatic prototype generation. The prototype implementation of the con-ceptual specification of the simple agents has been used to replicate, and extend, one of the experiments reported by Cesta et al.     

Model transformations across views

Models of software often describe systems by a number of (partially) orthogonal views: a state machine, a class diagram, a scenario might specify different aspects of the one system to be built. Such abstract, multi-view models are the starting point for transformations into platform-specific models and finally the code. However, during these transformations it is usually not possible to keep such a neat separation into different views: the specification language of the target models might not support all such views. The target model, however, still needs to preserve the behaviour of the abstract, multi-view model. Therefore, model transformations have to be capable of moving aspects of the behaviour across views.In this paper, we study model transformations migrating aspects from state-based views (i.e., class specifications with data and methods) to protocol-based views (i.e., process specifications on orderings of methods) and vice versa. The specification languages for these two views are equipped with a joint, formal semantics which enables a proof of behaviour preservation. We consequently derive conditions for our transformations to be behaviour-preserving, where behaviour preservation is characterised by refinement.     

Holistic methodology using computer simulation for optimisation of machine tools

Virtual machine concepts supporting optimisation of machine tools have been developed in earlier work. The virtual machine concept is a tool that can describe the behaviour of a machine tool while considering the interaction between mechanics of the machines and the control system. Considerable amount of work has been done proving the concept and showing the potential of such a design tool in different contexts. Several studies have shown the potential of using the virtual machine concept, although, no work has been found that is exploring the potential of a full optimisation study.     

A Bayesian support tool for morphological design

Dynamic computer based support tools for the conceptual design phase have provided a long-standing challenge to develop. This is largely due to the ‘fluid’ nature of the conceptual design phase. Design evaluation methods, which form the basis of most computer design support tools, provide poor support for multiple outcomes. This research proposes a stochastic-based support tool that addresses this problem. A Bayesian Belief Network (BBN) is used to represent the causal links between design variables. Included in this research is an efficient method for learning a design domain network from previous design data in the structure of a morphological design chart. This induction algorithm is based on information content. A user interface is proposed to support dynamically searching the conceptual design space, based on a partial design specification. This support tool is empirically compared against a more traditional search process. While no compelling evidence is produced to support the stochastic-based approach, an interesting broader design search behaviour emerges from observations of the use of the stochastic design support tool.