MOON is a design method suitable for real-time systems that supports concurrency and asynchronous communication. A MOON design specifies the structure of the software system, the hardware resources and the allocation ...
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MOON is a design method suitable for real-time systems that supports concurrency and asynchronous communication. A MOON design specifies the structure of the software system, the hardware resources and the allocation of software components to hardware resources. Performance evaluation is very important throughout the development of a real-time system. Program resource mapping nets (PRM-Nets) are a timed Petri net formalism used for performance evaluation studies. PRM-Nets are integrated performance models recognising the influence of the software structure, physical resources and mapping between software elements and physical resources on performance. Simulation of PRM-Nets allows estimates of response time, throughout and resource utilisation for a variety of hardware configurations to be investigated. The paper proposes the use of PRM-Nets for performance evaluation studies during a MOON design. The transformation of MOON activities and IDAs to PRM-Net performance models is outlined, and the modelling of hardware resources is considered.
Paragon is a notation for specifying object behaviours using sets of rewrite rules, where rewriting is controlled by synchronous and asynchronous message passing, and where objects may be dynamically created as a rewr...
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Paragon is a notation for specifying object behaviours using sets of rewrite rules, where rewriting is controlled by synchronous and asynchronous message passing, and where objects may be dynamically created as a rewriting side-effect. This paper overviews Paragon, and introduces a simple classification scheme for analysis of Paragon specifications. Restrictions on specifications are discussed in consideration of implementation feasibility and efficiency constraints. Implementation schemes based on the analysis and restrictions are defined. In particular, a translation strategy for static systems is detailed and motivated with a worked example. To reinforce the low-level nature of the derived implementation the translation is defined in terms of a digital hardware description language. Schemes for the implementation of general dynamic systems are also considered.
Conventional object-oriented design methodologies lead to a hierarchy of classes, but do not suggest which classes/objects should be loaded on which processors in a distributed system. We present the Decomposition Cos...
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Conventional object-oriented design methodologies lead to a hierarchy of classes, but do not suggest which classes/objects should be loaded on which processors in a distributed system. We present the Decomposition Cost Evaluation Model (DCEM) as an approach to this problem. DCEM brings the mapping problem to a higher level of abstraction where the question is which classes, rather than which tasks, should be loaded on which processors. To support these decisions we define communication and computation cost functions for objects, classes, and hierarchies. We then introduce Confined Space Search Decomposition (CSSD) which enhances parallel operations of applications utilizing a tree topology for the processor interconnection scheme. To reduce the penalties of load imbalance, we include a distributed dynamic load balancing heuristic called object Reincarnation (OR) in which no additional communication costs are incurred.
In this paper, we describe the traffic simulation system which analyzes a traffic flow in a road network. The system is constructed and operated on the parallel computer AP1000. A database of a road network is impleme...
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In this paper, we describe the traffic simulation system which analyzes a traffic flow in a road network. The system is constructed and operated on the parallel computer AP1000. A database of a road network is implemented with the object-oriented programming technique. Elements of a road network are regarded as objects, and vehicles which move on the lanes are regarded as attributive data. The database is divided into sub-databases and assigned to each processor. The system calculates the behavior of vehicles in parallel, Sending and receiving data among the objects are carried out with message passing on the communication network, Moreover, we show the results of the vehicles behavior, and evaluate the parallel efficiency.
Recently, the notion of having programming languages and computational systems that allow their programs to reason about themselves and reflect on their computations has attracted the attention of many researchers. Th...
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Recently, the notion of having programming languages and computational systems that allow their programs to reason about themselves and reflect on their computations has attracted the attention of many researchers. These systems, called "Reflective Systems", promise many advantages over conventional systems. For example, dynamic program stepping, execution tracing, and code analysis and modification at run time are few of the reflective operations that can be easily implemented in reflective systems. Reflectivity of programming languages allows the language users to extend the language to support other programming paradigms. Reflective systems can also play an important role in programming solutions for non-conventional domains. Artificial intelligence applications, particularly learning systems, benefit from the reflectivity of a programming language. A learning system must be able to modify itself at run time to incorporate its learned behaviors. The goal of this article is to define reflection and its components, introduce the appropriate terminology, and present briefly some reflective applications in object-oriented systems.
This paper presents a new conception for a distributed task-oriented real-time operating system comprising a compiler, an operating system kernel and communication packages. The system TOROS supplies the tools for a u...
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This research investigates the general user interface problems in using networked services. Some of the problems are: users have to recall machine names and procedures to. invoke networked services; interactions with ...
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This research investigates the general user interface problems in using networked services. Some of the problems are: users have to recall machine names and procedures to. invoke networked services; interactions with some of the services are by means of menu-based interfaces which are quite cumbersome to use; inconsistencies exist between the interfaces for different services because they were developed independently. These problems have to be removed so that users can use the services effectively. A prototype system has been developed to help users interact with networked services. This consists of software which gives the user an easy and consistent interface with the various services. The prototype is based on a graphical user interface and it includes the following appJications: Bath Information & Data Services; electronic mail; file editor. The prototype incorporates an online help facility to assist users using the system. The prototype can be divided into two parts: the user interface part that manages interactlon with the user; the communicatIon part that enables the communication with networked services to take place. The implementation is carried out using an object-oriented approach where both the user interface part and communication part are objects. The essential characteristics of object-orientation, - abstraction, encapsulation, inheritance and polymorphism - can all contribute to the better design and implementation of the prototype. The Smalltalk Model-View-Controller (MVC) methodology has been the framework for the construction of the prototype user interface. The purpose of the development was to study the effectiveness of users interaction to networked services. Having completed the prototype, tests users were requested to use the system to evaluate its effectiveness. The evaluation of the prototype is based on observation, i. e. observing the way users use the system and the opinion rating given by the users. Recommendations to improve further
Many entities in the real world that a software system has to interact with, e. g., for controlling or monitoring purposes, exhibit different behaviour phases in their lifetime, in particular depending on whether or n...
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Many entities in the real world that a software system has to interact with, e. g., for controlling or monitoring purposes, exhibit different behaviour phases in their lifetime, in particular depending on whether or not they are functioning correctly. That is, these entities exhibit not only a normal behaviour phase but also one or more abnormal behaviour phases associated with the various faults which occur in the environment. These faults are referred to as environmental faults. In the object-oriented software, real-world entities are modeled as objects. In a class- based object-oriented language, such as C++, all objects of a given class must follow the same external behaviour, i. e., they have the same interface and associ- ated implementation. However this requires that each object permanently belong to a particular class, imposing constraints on the mutability of the behaviour for an individual object. This thesis proposes solutions to the problem of finding means whereby objects representing real-world entities which exhibit various be- haviour phases can make corresponding changes in their own behaviour in a clear and explicit way, rather than through status-checking code which is normally embedded in the implementation of various methods. Our proposed solution is (i) to define a hierarchy of different subclasses related to an object which corresponds to an external entity, each subclass implementing a different behaviour phase that the external entity can exhibit, and (ii) to arrange that each object forward the execution of its operations to the currently appropri- ate instance of this hierarchy of subclasses. We thus propose an object-oriented approach for the provision of environmental fault tolerance, which encapsulates the abnormal behaviour of "faulty" entities as objects (instances of the above mentioned subclasses). These abnormal behaviour variants are defined statically, and runtime access to them is implemented through a delegation mechanism whic
The paper refers to the description of an object-oriented approach to the formalisation of parallel DEDS modelling tools. The goal of the presented approach is to develop a modelling framework that enables the modular...
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The paper refers to the description of an object-oriented approach to the formalisation of parallel DEDS modelling tools. The goal of the presented approach is to develop a modelling framework that enables the modular and hierarchical construction of complex DEDS with the structured view of the underlying state space. The basic notions are defined, e.g., the state classes, the dynamic model of the objects and the operation of the parallel composition. The parallel composition of the objects’ models express the dynamic relations between objects of different classes in dependence on theirs states and occurred events. The method of the analysis of the model concerning to the reachability of the given configuration is also discussed. This point will be the further step of the research activity. At the end, a simple example and its program realisation in the C++ language is given.
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