基于范畴论的形式语言模型建模方法研究

形式语言模型转换的语义一致性与其形式系统完备性分析是当前形式语言理论尚未有效解决的难题。针对形式语言模型的应用需求与研究现状,建立形式文法模型及其形式语言模型,应用范畴论方法构建具有普适意义的形式文法模型范畴与形式语言模型范畴。在形式语言族模型的形式化理论框架内,用与特定形式语言无关的范畴论方法研究形式语言模型转换的语义一致性。初步分析形式系统的完备性,通过与形式语言理论主要研究方法的比对论证了范畴论方法的优势,为形式语言模型的范畴论方法研究提供一个便利、高效的形式化理论框架。     

时态数据库的可视化方法与技术

1 引言时态数据库是将时间的概念结合到传统的数据库中。近十年来,人们对此所作的许多研究主要集中在把关系数据模型扩展为时态模型以及(或)把关系查询语言SQL和Quel扩展为时态的模式。除了强调关系模型之外,也有一些研究是将ER和其他的语义数据模型扩展到时态方面。时态数据模型的形式化和时态数据库的物理数据组织结构也受到了人们的关注。     

一种数据模型的范畴论建模方法

针对数据模型复杂语义建模的应用需求, 以及目前数据模型范畴论建模方法理论研究与工程实践方面存在的不足, 建立了一种素描数据模型。该模型在模型范畴的形式化框架内, 用与特定数据库建模语言无关的范畴论对数据库状态的一致性转换进行了形式化描述, 扩展了传统ER模型的表示与处理功能。基于素描对图形化建模规范的支持, 设计了ER模型向素描数据模型转换的算法, 以精确的语义联系保证模型转换的语义完整性, 并通过实验与对比分析了素描数据模型与算法的优势, 为数据模型的范畴论建模方法研究提供便利、高效的形式化理论框架。     

基于时态变量对象关系模型及代数运算

时态数据处理多是基于关系数据库平台,时态数据库模型也以时态关系数据模型为主.关系数据模型难以处理具有复杂类型的数据对象,而面向对象数据模型还缺乏商业化应用平台.现有关系数据库平台大多增加了面向对象基本功能,形成了对象关系数据库系统,因此将对象关系数据模型进行时态扩充就显得十分必要和具有可行性.首先在现有时态关系数据模型基础上,提出了一种基于对象关系双时态数据模型,而这种数据模型适合于在现有数据库平台上实现;其次,在该模型框架内,讨论了时态对象关系模式与时态关系模式相互间的联系与转换,这也是由时态关系扩充到对象关系的基本要求;再次,分析了时态模型中时态变量复杂语义和相应绑定算法,这是时态数据库能够有效运行的基本课题之一;最后,研究了基于时态变量复杂语义的时态对象关系数据操作代数,从而为时态对象关系模式的查询进行了必要的理论探讨.     

形式语言基于Monads的语义计算模型

传统形式语言的语义建模方法在语义解释与规则描述等语义计算方面存在不足,应用范畴论方法的Monads对形式语言的语义计算进行了研究。基于Monads构造Kleisli范畴,在Kleisli范畴的形式化框架内建立语义计算模型,并对该模型进行了应用。与传统语义建模方法相比,所提语义计算模型具有普适性,其语义解释与规则描述的能力更强。     

基于BCDM的双时态关系代数

双时态概念数据模型BCDM是一种重要的时态数据库模型，基于BCDM模型，建立了一种双时态关系代数．首先，对时态数据库事务时间和有效时间进行规范化的定义，给出BCDM中时间元素的规范化定义和演算描述；而后，定义时态映射，用以描述BCDM中的双时态元组，并形式描述时态映射的演算；最后，用时态映射定义的元组对双时态关系进行定义，并由此给出双时态关系代数运算的形式化描述．     

时空数据表达研究

描述了目前时态数据模型和时空数据模型的发展,现已共识时态是任何信息的一个重要属性,但是时态数据库中时态关系代数的基本思路是通过在关系模式上显式化时变语义来进行简单结构的时态数据建模,而时空数据建模中时态对象代数是在对象结构上显式化时变语义来进行复杂结构的时态数据建模,并深入探讨了时空数据模型中地理信息的时间维表达方式,指出了各种时空数据模型存在的主要问题。     

RBAC模型中条件时态的研究与设计

具有时态特征的角色访问控制（RBAC：Role Based Access Control）模型能够为RBAC控制机制提供动态的时间控制因素，是目前安全模型领域的研究热点。基于对周期理论和时态RBAC模型的研究，本文认为时态不仅能够为模型提供时间维的控制因素，而且模型中的约束也能作用于时间雏形成条件时态平面的控制因素，从而能够进一步提高模型控制的灵活性和多样性。为此，本文提出了条件周期表达式和条件时态的概念，形式化描述了条件时态语义；并通过条件周期事件和角色状态在条件周期下的断言详细论述了条件时态。     

语义不确定时态跨度的规范化处理及近似运算

不确定时态的语义处理及近似运算是时态系统的研究与应用中不可忽视的基本问题.不确定语义的转换、时态粒度的规范化以及不确定时态间的近似运算和语义还原成为不确定时态信息处理中的难点.针对时态跨度中不确定语义造成的时态不确定性与多样性,提出了对不确定语义进行转换的思想,将其转换为区间数的形式,结合时态的粒度属性,给出了不确定时态跨度的形式化描述,使其成为可计算问题;根据时态粒度约束对不确定时态跨度进行了规范化处理,使其可以参与运算;最后结合时态区间数给出了不确定时态跨度间的运算及语义还原方法,有效地处理了不确定时态跨度间的复杂运算,典型的运算过程均给出了示例予以说明.     

基于代数-时态逻辑的象形对象研究

本文首先讨论了国内外有关面向对象方法学、代数规范、时态逻辑的研究现状 ,分析了对象形式化语义研究的不足 .其次 ,分析了几种主要的系统形式化模型和方法 .然后 ,在我们已研究的“计算机甲骨文象形码输入法”的基础上 ,从时态逻辑的角度定义了象形对象及其约束条件 ,定义了面向对象的有色 Petri网 (OOPEN) ,并应用 OOPEN描述了象形对象的层次结构 .最后 ,我们将代数规范与时态逻辑相结合 ,对象形对象的语义基础进行了一些研究 .     

Formalizing visual interaction with historical databases

Recent database applications are typically oriented towards a large set of non-expert users, and therefore, they need to be equipped with suitable interfaces facilitating the interaction with the system. Moreover, the incorporation of the time dimension in database systems is a desirable feature. Indeed, several temporal data models and the corresponding textual query languages have been proposed. However, there is a limited amount of research concerning the investigation of user-oriented languages for querying temporal databases. Our proposal addresses such a need. In particular, we propose a visual query environment, namely Temporal Visual Query Environment (TVQE) which provides an easier interaction of the user with temporal databases. The system adopts a diagrammatic representation of the database schema (including temporal classes and relationships) and a “graphical notebook” as interaction metaphor. In our approach, non-database experts are released from syntactical difficulties which are typical of textual languages, and they can easily express temporal queries by means of elementary graphical operations (e.g. click on a node label). Differently from many proposals in the field of visual query languages, the language underlying TVQE is provided with formal syntax and semantics. It is based on a minimal set of temporal graphical primitives (TGPs), which are defined on a Temporal Graph Model (TGM), with visual syntax and object-based semantics. In this paper we mainly concentrate on the formal aspects of TVQE, and provide some hints on the visual interaction mechanisms and implementation issues.     

Process time patterns: A formal foundation

Companies increasingly adopt process-aware information systems (PAISs) to model, execute, monitor, and evolve their business processes. Though the handling of temporal constraints (e.g., deadlines or time lags between activities) is crucial for the proper support of business processes, existing PAISs vary significantly regarding the support of the temporal perspective. Both the formal specification and the operational support of temporal constraints constitute fundamental challenges in this context. In previous work, we introduced process time patterns, which facilitate the comparison and evaluation of PAISs in respect to their support of the temporal perspective. Furthermore, we provided empirical evidence for these time patterns. To avoid ambiguities and to ease the use as well as the implementation of the time patterns, this paper formally defines their semantics. To additionally foster the use of the patterns for a wide range of process modeling languages and to enable pattern integration with existing PAISs, the proposed semantics are expressed independently of a particular process meta model. Altogether, the presented pattern formalization will be fundamental for introducing the temporal perspective in PAISs.     

Modal Change Logic (MCL): Specifying the reasoning of knowledge-based systems

We investigate the formal specification of the reasoning process of knowledge-based systems in this paper. We analyze the corresponding parts of the KADS specification languages KARL and (ML)² and deduce some general requirements. The essense of these languages is that they integrate a declarative specification of inferences with control information. The languages differ in the way they achieve this integration and each of them has shortcomings. We propose a unifying semantical framework that integrates the core of the different solutions and overcomes their problems. We define a semantics and axiomatization with the Modal Change Logic (MCL). The main contribution of the paper is not to introduce yet another specification language. Instead we aim at four goals: (1) defining a framework for describing the dynamic reasoning behavior of knowledge-based systems which integrates existing approaches; (2) defining a semantics for the specification of the dynamic reasoning behavior of a knowledge-based system within the states as algebras setting that overcomes several shortcomings and ad hoc solutions of existing approaches; and (3) providing an axiomatization that enables the development of mechanized proof support. (4) Through conceptual and semantical clarity, we investigate the relationships to similar work in software engineering and database engineering opening possibilities for further cross-fertilization of these fields.     

Use of a formal notation for static semantics in compiler design

Formal notations for the specification of the syntax and the dynamic semantics of languages exist and are of great benefit to the compiler writer. However, formal notations for the static semantics of languages have tended to be tools of the language designer and of little practical significance to the compiler writer. This paper describes how a particular notation was used to assist in the implementation of a Cobol compiler and of an interpreter for a simulation language.     

A formal approach to object-oriented databases

Object-oriented database systems are the focus of current research and development efforts. Yet, there is no commonly accepted object model, nor is it clear whether such a model can be developed. This paper reports on efforts to develop a formal framework that contains most features found in current object oriented database systems. The framework contains two parts. The first is a structural object model, including concepts such as structured objects, identity, and some form of inheritance. For this model, we explain the distinction between values and (abstract) objects, describe a system as a directed graph, and discuss declarative languages. The second part deals with higher-order concepts, such as classes and functions as data, methods, and inheritance. This part is a sketch, and leaves many issues unresolved. Throughout the paper, the emphasis is on logic-oriented modeling.     

Garment中的归约语义

文中用代数方法研究了Ｇａｒｍｅｎｔ中程序设计语言的归约语义，首先给出了归约语义在形式语言理论中的含义，然后提出了Ｇａｒｍｅｎｔ中语言的代数模型。在此代数模型下讨论了归约语义及其性质，并给出了语言可归的充分条件。