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1.
分布式多媒体系统的关键问题探讨与研究   总被引:1,自引:0,他引:1  
依据多媒体时间模型和同步模型,面向对象的并发系统和分布式系统的研究已经取得不少结果。但由于特殊的要求,这些结果已不能满足实际应用的需要,为此,我们就分布式多媒体系统中的同步这一关键问题进行了研究。本文首先论述了形式化规范语言LOTOS的基本概念与约定,对其进行了基于时间的改进和扩充,引入了离散时间域和时间操作算子,然后确定其相应的语法定义和语义规则,通过仔细分析分布式环境下的多媒体同步问题,基于时间扩充的LOTOS,给出了一种特殊的多媒体同步系统以及具体的算法描述,通过实例对分布环境下多媒体信息同步问题在实际中的应用进行了深入的探讨。  相似文献   

2.
扩展时间流Petri网多媒体同步模型   总被引:5,自引:0,他引:5  
多媒体同步的一个主要问题是多媒体同步时间要求的描述与建模。文中基于时间流Petri网模型(TSPN),通过分析TSPN模型的不足之处,提出了一种新的多媒体同步模型--扩展时间流Petri网模型(STSPN),STSPN不但可以完全、准确地描述媒体流内和流间的时间行为,而且通过引入容许阻塞时间、问题算法等对TSPN进行扩展,可以有铲地克服网络随机延迟、阻塞和丢包等因素的不良影响,提高了模型的建模能力  相似文献   

3.
XOCPN:支持用户交互的多媒体同步模型   总被引:1,自引:0,他引:1       下载免费PDF全文
多媒体同步是多媒体应用的一个重要需求。本文对OCPN模型进行了扩展,提出了一种基于时间Petri网的多媒体同步模型XOCPN,以对具有时间约束关系的多媒体合成进行规范描述,并具有支持灵活用户交互的能力。文中给出了处理异步用户交互的算法,并用示例说明。  相似文献   

4.
本文描述了一种基于PROLOG的专家系统建造工具库PTES的实验系统。PTES是用PROLOG编写的,该系统根据支持基于规则的知识表示及近似推理对PROLOG的知识处理能力进行了扩充。PTES的推理机制使用了可能性能逻辑及模糊集合理论作为其逻辑基础,并以一种形式化的方法提供了处理非确定事实及非确定规则的能力。  相似文献   

5.
本文描述了一基于PROLOG的专家系统建造工具库PTES的实验系统。PTES是用PROLOG编写的,该系统根据支持基于规则的知识表示及近似推理对PROLOG的知识处理能力进行了扩充。PTES的推理机制使用了可能性逻辑及模糊集合理论作为其逻辑基础并以一种形式化的方法提供了处理非确定事实及非确定规则的能力。  相似文献   

6.
基于类比的学习式搜索算法AMO.GLSA   总被引:1,自引:0,他引:1  
本文首先给出了学习式搜索的一个问题模型,然后(5)中GLS搜索解题系统的基础上,本文描述了一个多目标学习搜索算法MO.GLSA,并对该算法作出一性能评价,最后,文中给出了一个基于类比的学习搜索算法AMO.GLSA。  相似文献   

7.
杨周南  何江 《微机发展》1995,5(1):14-18
本文提出了一种面向屏幕的辅助软件工具DTOOL的总体结构,主要功能、实现方法、生成机制、开放效益及在DTOOL环境下开发MIS时有关应用系统概念模式的建立步骤,本文重点讨论在DFD及功能分解后如何进一步的建立IDS及TDS并最终地产生一棵面向屏幕设计的结构构树,这种开发思路将有助于一切其它面向屏幕的软件工具环境下对MIS开发的概念模式的描述,这将大大提高软件开发效率,改善开发和维护性能。  相似文献   

8.
基于Petri网的分布式多媒体同步模型研究   总被引:3,自引:0,他引:3  
Petri网作为一种描述系统行为的形式化工具,在各类多媒体系统中有着较多的应用,尤其擅长于描述多媒体的同步问题,出现了诸如OCPN(对象组合Petri网)等多媒体同步模型,然而,这些模型却不足以处理分布式环境中的多媒体同步问题。本文提出了一种新的扩充Petri网模型并分析了其模型化的能力和性质,利用该模型可以较好地解决分布式环境中的多媒体同步问题。  相似文献   

9.
本文讨论如何在LOTUS NOTES数据库中实现主动推出式多媒体播发技术,从而通过浏鉴器文档的主动推出式播发,其中涉及的技术有CGI、LOTUS NOTES HITEST API等,使得该播发技术具有文档自动切换、多媒体播发、自动滚屏等功能。  相似文献   

10.
文章针对分布式多媒体应用所含的复杂时态关系和分布性特性,利用同步代理构建了一个基于代理的分布式多媒体同步规划系统。并通过对传统Petri网的扩展,对分布式同步Petri网(DSPN)进行了定义,并利用DSPN对同步代理进行建模。最后通过对多媒体应用实例的分析,简要说明系统的操作流程。  相似文献   

11.
LOTOS is an executable specification language for distributed systems currently being standardized within ISO as a tool for the formal specification of open systems interconnection protocols and services. It is based on an extended version of Milner's calculus of communicating systems (CCS) and on ACT ONE abstract data type (ADT) formalism. A brief introduction to LOTOS is given, along with a discussion of LOTOS operational semantics, and of the executability of LOTOS specifications. Further, an account of a prototype LOTOS interpreter is given, which includes an interactive system that allows the user to direct the execution of a specification (for example, for testing purposes). The interpreter was implemented in YACC/LEX, C and Prolog. The following topics are discussed: syntax and static semantics analysis; translation from LOTOS external format to internal representation; evaluation of ADT value expressions and extended CCS behaviour expressions. It is shown that the interpreter can be used in a variety of ways: to recognize whether a given sequence of interactions is allowed by the specification; to generate randomly chosen sequences of interactions; in a user-guided generation mode, etc.  相似文献   

12.
王继曾  张键 《微机发展》2004,14(2):78-81
形式描述技术在协议设计中的应用是至关重要的和必不可少的,为形式规范确定一个合适的结构又是应用此技术的关键步骤,基于此文中重点研究了基于LOTOS技术的形式结构模型的创建方法。简要介绍了开发网络协议的形式描述技术、网络协议的结构概念、等级抽象和LOTOS描述规范风格。基于LOTOS技术,提出了网络协议开发过程中形式结构模型的创建原则和方法,此方法结合LOTOS语言特征,应用其描述规范风格,融协议结构、逐步改进和等级抽象为一体,简化了所开发协议的验证、测试和实现的复杂性。  相似文献   

13.
谢冰  陈火旺  王兵山 《软件学报》1999,10(6):642-646
基于LOTOS规范语言,文章从系统功能规范出发,结合实际系统的分布特性,推导出符合实际系统结构的模块化规范的转换方法.用标注的完全LOTOS语言规范表达复杂的系统分布特性,研究了使用广播通信方式进行协同的、直接处理多模块划分的规范分解算法.  相似文献   

14.
A new tool for generating implementation prototypes of communication protocols and concurrent systems specified using the ISO LOTOS language is presented in this paper. A brief introduction to LOTOS and a discussion of the main problems related to the efficient execution of specifications written in LOTOS are presented first. The design and implementation of the tool are then considered: LOTOS specifications are analysed and translated into C functions which are executed by co-operating processes in the Unix environment. The set of LOTOS process definitions is first translated into a suitable number of extended finite-state machines (EFSMs). The method proposed allows the problem of deriving unbounded EFSMs to be circumvented and a sort of control on the process number/size trade-off to be obtained at the same time. The problem of implementing the LOTOS multi-way rendezvous mechanism for process synchronization is solved by using an algorithm based on message-passing techniques. An example of prototype derivation is also described, showing the form of C code generated by translating a simple specification. Finally, some performance figures are presented.  相似文献   

15.
Summary.  A complete communication system is broken down into a number of protocol layers each of which provides services to the layer above it and uses services provided by its underlying layer. A service specification defines a particular ordering of the operations that a given layer provides to the layer above it. The active elements in each layer are called entities and they use a protocol in order to implement their service definition. On the basis of this relation between the service and protocol concepts we have developed algorithms for deriving protocol entity specifications from a formal service specification. The derived protocol entities ensure the correct ordering of the service primitives by exchanging synchronization messages through an underlying communication medium. This paper presents an extended version of our earlier derivation algorithms. This version of the algorithm can handle all operators and unrestricted process invocation and recursion as defined by basis LOTOS. The correctness of this derivation algorithm is formally proved. Received: January 1992 / Accepted: February 1996  相似文献   

16.
17.
王继曾  张键 《计算机工程》2005,31(12):97-99
LOTOS形式规范的目标实现是协议设计中必不可少的阶段之一。该文对基于LOTOS的形式描述规范的实现方法进行了研究,包括目标实现环境的特点、实现中的空白因素、抽象模型到实现模型的转换、规范的最终目标实现,并对如何将LOTOS规范转换为C、C 语言实现进行了探讨。  相似文献   

18.
针对BPEL并发同步引发的数据竞争、流程阻塞等问题,提出了一种BPEL结构演化算法。该算法的基本思想是利用BPEL基于XML编写的事实,使用XML 解析工具对BPEL的结构进行调整,达到规避失败的同步过程,删除冗余link结构的目的。利用自主开发的转换工具实现BPEL到形式化描述语言LOTOS的转换,通过对演化前后的BPEL流程做模型检测,来验证该演化方法的可行性。实验结果表明BPEL结构演化算法能够有效缓解BPEL并发同步带来的数据竞争、流程阻塞问题。  相似文献   

19.
This paper describes the specification of an input model for graphics systems. The initial aim of the work reported in this paper was to revise the input model adopted by graphics standards by means of formal specification techniques in order to acquire a deep knowledge of its capabilities, to eventually discover errors and to develop improvements. Taking into account similar works done in this area by others and considering a number of major issues related to input recently discussed within the graphics community, a new model is being proposed that addresses the very key concepts of parallelism, extensibility and reconfigurability. The model is based upon composition operations defined over basic components specified as a set of concurrent processes. Composition operations and process definitions have been formally specified by using the LOTOS notation and investigated by means of the LOTOS Interactive Tools Environment. In the first part of the paper, the input model of graphics standards is shortly examined in the light of the results so far achieved by related works on formal specification of computer graphics systems. Subsequently, an improved model is presented. Finally, its capability of simulating the traditional operating modes of logical input devices and a methodology for defining new operating modes is demonstrated.  相似文献   

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