基于QVT的模型转换方法研究

针对不同模式之间规则不能重用甚至无法描述嵌套模式的问题．提出一种基于扩展MOF元模型与扩展QVT语言相结合的模型转换方法。该方法通过扩展MOF元模型解决模型之间规则不能重用问题．通过扩展QVTRelations可以增强规则语言的有效性,为模型建立和模型转换提供一种更有效的途径。在一个股票交易系统的转换应用实例中验证该方法的正确性。     

Extending lexical association measures for collocation extraction

Collocations are linguistic phenomena that occur when two or more words appear together more often than by chance and whose meaning often cannot be inferred from the meanings of its parts. As collocations have found many applications in the fields of natural language processing, information retrieval, and text mining, extracting them from large corpora has been the focus of many studies over the past few years. In this paper, we introduce the notion of an extension pattern, a formalization of the idea of extending lexical association measures (AMs) defined for bigrams. An extension pattern provides a measure-independent way of extending AMs for extracting collocations of arbitrary length. We define different extension patterns and compare them on a task of extracting collocations from a newspaper corpus. We show that the stopword-sensitive extension patterns we propose outperform other extensions, which indicates that AMs could benefit by taking into account linguistic information about an n-gram’s part-of-speech pattern.     

Notions of Sameness by Default and their Application to Anaphora, Vagueness, and Uncertain Reasoning

We motivate and formalize the idea of sameness by default: two objects are considered the same if they cannot be proved to be different. This idea turns out to be useful for a number of widely different applications, including natural language processing, reasoning with incomplete information, and even philosophical paradoxes. We consider two formalizations of this notion, both of which are based on Reiter’s Default Logic. The first formalization is a new relation of indistinguishability that is introduced by default. We prove that the corresponding default theory has a unique extension, in which every two objects are indistinguishable if and only if their non-equality cannot be proved from the known facts. We show that the indistinguishability relation has some desirable properties: it is reflexive, symmetric, and, while not transitive, it has a transitive “flavor.” The second formalization is an extension (modification) of the ordinary language equality by a similar default: two objects are equal if and only if their non-equality cannot be proved from the known facts. It appears to be less elegant from a formal point of view. In particular, it gives rise to multiple extensions. However, this extended equality is better suited for most of the applications discussed in this paper.     

Operational Semantics for MSC'96

Recently, the ITU-standardised specification language Message Sequence Chart has been extended with constructs for more complete and structured specifications. The new version of the language is called MSC'96. Currently, research is performed on the extension of the formal semantics towards a semantics for MSC'96. In this article, we aim at explaining the basic ideas behind the formal semantics. We give formal definitions of parts of the language, but most features are explained by informal examples and drawings. It takes several steps in order to follow the path from an MSC drawing to its formal meaning. First, the drawing must be converted to a concrete textual representation. This conversion is already defined implicitly in Z.120. Next, this syntax is transformed into a formal expression over some process algebra signature. MSC constructs are replaced by appropriate process algebra operators. This transformation is compositional. The operational behaviour of the process algebraic expression can be studied, or the expression can be interpreted into some mathematical model and compared to the interpretation of some other MSC.     

A dynamic C-based object-oriented system for Unix

Calico, a C-based object-oriented language supported by an integrated software development environment, is described. Calico features strict encapsulation, dynamic binding, fast garbage collection, and interoperability with C. It provides a simple, uniformly applied object model, a syntax easily mastered by C programmers, a new multiple inheritance model, simple method-call semantics with some novel extension and effective support for the team development process. Although Calico introduces some unique language features, its primary contribution is the productivity advantage that this feature integration provides for the Unix/C environment     

A rule based knowledge transaction model for mobile environments

In this paper, we propose and formalize a rule based knowledge transaction model for mobile environments. Our model integrates the features of both mobile environments and intelligent agents. We use logic programming as a mathematic tool and formal specification method to study knowledge transaction in mobile environments. Our knowledge transaction model has the following major advantages: (1) It can be used for knowledge transaction representation, formalization and knowledge reasoning in mobile environments. (2) It is knowledge oriented and has a declarative semantics inherited from logic programming. (3) It is a formalization that can be applied to general problem domains. We show that our model can be used for knowledge transaction representation, formalization and knowledge reasoning in mobile environments.     

面向方面分布式系统形式化规格说明语言

分布式系统复杂性的不断增加以及对可配置性和可重用性要求的不断提高,需要面向方面软件工程方法的支持,而形式化方法能保证分布式系统的正确性。本文对分布式规格说明语言Ocsid进行了面向方面的扩展,讨论了面向方面的Ocsid的框架结构、语法要求、方面的联结和功能接口。定义了面向方面的Ocsid规格说明语言中叠加和组合的形式化描述,该形式化描述覆盖了各个精化阶段,使精化体系的各个独立视点被协调地组合,并能形式化地验证规格说明的时态属性和系统行为。本文的工作针对的是分布式系统的形式化规格说明,提出了面向方面Ocsid的形式基础和方面扩展,其基本思想同样适用于更一般的情况。     

Statistical model checking of Timed Rebeca models

The actor-based language, Timed Rebeca, was introduced to model distributed and asynchronous systems with timing constraints and message passing communication. A toolset was developed for automated translation of Timed Rebeca models to Erlang. The translated code can be executed using a timed extension of McErlang for model checking and simulation. In this work, we added a new toolset that provides statistical model checking of Timed Rebeca models. Using statistical model checking, we are now able to verify larger models against safety properties compared to McErlang model checking. We examine the typical case studies of elevators and ticket service to show the efficiency of statistical model checking and applicability of our toolset.     

基于MDA的UML模型转换:从功能模型到实现模型

MDA（Model Drive Architecture）是OMG（Object Management Group）提出的解决系统集成问题的新途径，它以UML、MOF、CWM为核心，定义软件开发过程中的模型组织管理框架。本文探讨了MDA框架下在元模型层定义模型转换的方法。引入模型转换规则描述语言，给出模型转换规则应遵循的部分原则。以CORBA平台为例说明在元模型层用既定语言定义模型转换规则，从功能模型到实现模型的模型转换方法。基于以上方法构建相应的工具原型。     

使用SystemC2.0进行SoC设计建模仿真

系统级建模是大规模集成电路设计的一个重要阶段，它实现了设计从文本规范向功能实现的过渡，传统方法中一直使用硬件描述语言(HDL)来完成系统级建模，其弊端在于建模的效率低不适应如今SoC设计的要求。SystemC作为一种基于C 语言的新型硬件设计语言较已有的HDL语言在系统级建模、软硬件协调设计方面更具优势，因此也更适用于SoC的设计建模，该文介绍了SystemC的最新版本SystemC2．0的使用特点以及如何利用其进行SoC顶层设计的方法，并通过对一个短消息平台的建模实例说明如何具体使用SystemC2．0，通过与传统方法的比较可以得出结论，SystemC可以迅速有效地实现SoC系统级的建模。