7872291
Sensors and Actuators in TCOZ
Timed Communicating Object Z (TCOZ) combines Object-Z's strengths in modeling complex data and algorithms with Timed CSP's strengths in modeling real-time concurrency. TCOZ inherits CSP's channel-based communication mechanism, in which messages represent discrete synchronisations between processes. The purpose of most control systems is to observe and control analog components. In such cases, the interface between the control system and the controlled systems cannot be satisfactorily described using the channel mechanism. In order to address this problem, TCOZ is extended with continuous-function interface mechanisms inspired by process control theory, the sensor and the actuator. The utility of these new mechanisms is demonstrated through their application to the design of an automobile cruise control system.
5239234
The role of secondary attributes in formal object modelling
When modelling a large and complex system, clarity of the specification becomes an important factor. In object-oriented specification, the states of individual objects are captured by the values of their attributes. Frequently however, there are dependencies between the attributes of an object. An appropriate indication of which attributes are primary (independent) and which are secondary (dependent) can add significantly to clarity. This paper details the notion of secondary attributes, their roles and implications in formal object-oriented specification.
207130315
Formal Designs for Embedded and Hybrid Systems
The design of embedded and hybrid systems requires powerful mechanisms for modeling data, state, concurrency and real-time behaviour. The {first} part of this paper illustrates a powerful design notation Timed Communicating Object Z (TCOZ) that has both channel based and sensor/actuator based interfaces. We believe that TCOZ is well suited for presenting more complete and coherent design models for complex embedded and hybrid systems. However, the challenge is how to analyze and check these models with tools support. One effective approach is to project (transform) the design models into multiple domains, then to use existing specialized tools in those domains to perform the checking and analyzing tasks. The second part of this paper demonstrates one particular projection from TCOZ designs to Timed Automata (TA) models so that TA model checkers can be used to check time related properties.
18404140
Deep Semantic Links of TCSP and Object-Z: TCOZ Approach
Abstract. Formal methods can be used in effective combination only if the semantic links between individual methods are clearly established. This paper discusses the semantic design of TCOZ, a language blended from Object-Z and TCSP. The semantic model adopted is the infinite timed failures model of TCSP, extended to include initial state and update events for modelling operations on internal state. An infinite trace model has been used so as to ensure proper account is taken of the potentially unbounded non-determinism allowed by Z schemas.
18649413
Capturing periodic concurrent interactions of mission computer tasks
Safety critical systems, such as aviation systems controlled by software, often have hard real-time requirements. Producing the correct result at the right time is the fundamental goal of such systems. Formally specifying the system functions and the timing requirements is the crucial step towards achieving such a goal. Aviation systems often need to be modified or upgraded on a regular basis, i.e. functionality and timing constraints may be altered. Therefore, the formal specification of such systems needs to be easily reused, maintained and modified. This paper demonstrates how the task scheduling aspects of an aircraft mission computer can be formalised in TCOZ.
10062286
Integrating Object-Z with timed automata
When designing a complex system, Object-Z is a powerful logic-based language for modeling the system state aspects, and timed automata is an excellent graph-based notation for capturing timed control behaviour of the system. This paper presents an effective combination of the two techniques with novel composition and communication mechanisms. The combined notation enhances Object-Z with realtime modeling capability and also extends timed automata with enhanced structure and state modeling features.
38191842
Modeling of End-to-End Transmission of Astronomical Images over Lossy Network
17533115
A Behavioral Analysis Approach to Pattern-Based Composition
This paper introduces a rigorous analysis approach to software design composition based on automated verification techniques. We show how to represent, instantiate and integrate design components, and how to find design composition errors using model checking techniques. We illustrate our approach with a Web-based hypermedia case study since hypermedia documents and systems are now becoming complex software applications, which are component-based.
14829052
A formal framework for design component contracts
Building large software systems out of existing software components can save time and cost. These software components range from architectural and design components in different phases of software development. Component technologies lead to increasing productivity and flexibility. However, it also introduces significant problems in ensuring the integrity and reliability of these composed systems because of their complex software topologies, interactions, and transactions. In this paper, we concentrate on the pattern-based design components and their compositions, which are captured as contracts through a composition theory. More specifically, design component contract is defined based on process calculus and logic programming; the properties that related to the design component contract are captured, and tools are used to automatically verify these properties. This research will enhance the capabilities of formal system modeling and analysis by providing a rigorous basis for high-assurance integration of diverse pattern-based components.
6426341
Event-based blackboard architecture for multi-agent systems
Developing large multi-agent systems is a complex task involving the processes of the requirement, architecture, design and implementation of these systems. In particular, the architectural design is critical to cope with the increasing size and complexity of these systems. The multi-agent system that accesses a central repository is typically based on the blackboard architectural pattern. However, the control strategies of the agents are inherently complex. In this paper, we present an event-based control strategy to manage the access of central repository by multi-agents. In this approach, the blackboard pattern is composed with the implicit invocation pattern to separate the control policies from the control component so that the architecture is ease of evolution, reuses and changes.
17680274
Ensuring structure and behavior correctness in design composition
The design of a large component-based software system typically involves the composition of different components. Instead of relying on a free composition of components, we advocate that more rigorous analysis methods to check the correctness of component composition would allow combination problems to be detected early in the development process so that people can save considerable effort offering errors downstream. In this paper we describe a rigorous method for component composition that can be used to solve combination and integration problems at the (architectural) design phase of the software development lifecycle. In addition, we introduce the notion of composition pattern in order to promote the reuse of composition solutions to solve routine component composition problems. Once a composition pattern is proven correct, its instances can be used in a particular application without further proof. In this way, our proposed method involves reusing compositions as well as reusing components. We illustrate the utility of our approach through an example related to the composition of design patterns as design components. Structural and behavioral correctness proofs about the composition of some design patterns are provided.