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本文提出了一个面向对象的数据库系统的基本查询模型-OO代数,它具有关系代数相似的形式,具有封闭性和远比关系代数强得多的表达能力。文中首先给出了面向对象的数据库系统的数据结构的一种形式化描述-OSG,然后OO代数的五种基本运算:并、差、类间连接、类内选择及广义投影被一一定义,并说明了用关系代数实现这五种运算的方法。 相似文献
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一个演绎对象数据库SD-DOOD的设计与实现 总被引:2,自引:0,他引:2
通过探寻面向对象数据库与知识库技术相结合的途径,研究演绎对象数据库系统实现的关键技术。以基于演绎数据库系统SD-DDBS,设计实现了一个演绎对象数据库系统原型SD-DOOD。系统支持类、类层次、对象、属性、方法、继承和封装等面向对象数据库系统的核心概念,支持演绎对象等演绎数据库的概念,提供了图形用户接口(GUI),便于用户进行创建、查询等操作。 相似文献
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一个实现对象查询语言的形式化基础 总被引:1,自引:0,他引:1
在基于CORBA(common object request broker)的面向对象多数据库系统SCOPE/CIMS中,作者选择了对象数据库管理组ODMG(object database management group)提出的对象数据库标准ODMG-93的OQL(object query language)作为全局查询语言.为此,提出了一种实现OQL的形式化基础,包括适合建模OQL的一种对象演算和一种对象代数;对象演算的规范化规则和规范化步骤;对象演算与对象代数的等价映射规则及转换策略. 相似文献
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O2DB是一个开发出的面向对象数据库系统的核心原型,而对象标识是面向对象方法中的一个重要特征,对于OODB更为重要。文中着重阐述了面向对象数据库系统(OODBMS)O2DB中对象标识的设计与实现方法,详细介绍了对象标识的定义、性质,对于数据共享、数据一致性的作用以及在O2DB中的设计与实现方法。 相似文献
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本文提出关于复杂对象模拟的形式化理论.文中给出对象和型的广义数据模型以及型的重构定义,并将其概念从数据组织扩展到对象演算;讨论广义对象代数;提出符号对象模型以统一面向对象数据库系统对于对象的标识、管理和操作,以至于由多层次对象演算到一阶逻辑的映射.这一工作将为有关复杂对象的数学模型、操作代数和演绎推理的各种概念和方法构成具有连贯性和一致性的统一理论体系奠定了一定的基础. 相似文献
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本文根据视频信息的特点,通过对代数视频数据模型和面向对象的超媒体数据模型的整合,给出了一种面向对象的超媒体代数视频数据模型。该模型可进一步有利于数据库系统的操作和视频数据的处理。 相似文献
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本文根据视频信息的特点,通过对代数视频数据模型和面向对象的超媒体数据模型的整合,给出了一种面向对象的超媒体代数视频数据模型。该模型可进一步有利于数据库系统的操作和视频数据的处理。 相似文献
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本文根据视频信息的特点,通过对代数视频数据模型和面向对象的超媒体数据模型的整合,给出了一种面向对象的超媒体代数模型,该模型可进一步有利于数据库系统的听任和视频数据的处理。 相似文献
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本文根据视频信息的特点,通过对代数视频数据模型和面向对象的超媒体数据模型的整合,给出了一种面向对象的超媒体代数视频数据模型.该模型可进一步有利于数据库系统的操作和视频数据的处理. 相似文献
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The paper presents an algebraic specification of net objects. By net objects we mean those that are defined in object-oriented paradigms and those defined with nested relations in complex database models. An algebraic specification is set up that involves structures of net objects, accesses of net objects, and some features of object-oriented programming, such as multiple inheritance and polymorphism. Objects and their relationships are then characterized formally in the modeling, which utilizes the hierarchical approach in the algebraic theory of abstract data types, and is further developed by adding mechanisms from existing object systems. Categories of net objects are presented with the properties of accesses among them 相似文献
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面向对象的图象数据模型 总被引:5,自引:1,他引:4
本文按照图象数据的特点,基于构造性类型定义数据库模式,提出了面向对象的图象数据模型,该模型可以对图象实体的结构及其联系进行描述,并支持语义建模的机制,它为图象实体提供了完善的建模能力,本文还讨论了模型中对象操作的形式语义,给出了构造性类型上图象代数运算所具有的形式。 相似文献
13.
Chen Qiming 《计算机科学技术学报》1988,3(2):113-130
In this paper a generalized object-oriented approach for complex object modeling is proposed,which ischaracterized by adding the concept of Meta-Class into the object-oriented paradigm for unifying thehandling of object types and primary data models,and also characterized by integrating the modeling ofobject type hierarchy and object configuration hierarchy.Concepts such as Compositional RelationshipObject,Face,Object Configuration Schema Expression,Object Skeleton are introduced to specify objectstructure,to support high degree of object sharing and to offer high degree of data independence.Operationson the class hierarchy,the object configuration structures and the object instances are developed respectivelywith distinguished semantics.This approach provides an extended object-oriented framewerk for handlingcomplex objects in any AI or database system(?). 相似文献
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主要是以一种带权类依赖图作为面向对象系统的UML类图的抽象表示,其中类依赖图的各边上权值对应于类图中的相应关系。针对带权类依赖图运用代数图论中图的Laplace谱的连通特性以迭代分割的方式对其进行划分,得到所需开发的系统构件。通过实验表明,该方法是一种有效的面向对象软件系统分解方法,并且分解所得到的构件具有较高的内聚性。 相似文献
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Rajendra K. Raj Ewan Tempero Henry M. Levy Andrew P. Black Norman C. Hutchinson Eric Jul 《Software》1991,21(1):91-118
Emerald is a general-purpose language with aspects of traditional object-oriented languages, such as Smalltalk, and abstract data type languages, such as Modula-2 and Ada. It is strongly typed with a non-traditional object model and type system that emphasize abstract types, allow separation of typing and implementation, and provide the flexibility of polymorphism and subtyping with compile-time checking. This paper describes the Emerald language and its programming methodology. We give examples that demonstrate Emerald's features, and compare and contrast the Emerald approach to programming with the approaches used in other similar languages. 相似文献
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The basis for this paper are the concepts of parameterization and implementation of abstract data types which have been developed in the theory of algebraic specifications with initial algebra semantics. In this paper we combine both concepts defining implementations of parameterized data types and studying the compatibility of parameter passing and implementation of parameterized data types. In our main result we show that parameter passing commutes with implementation. This is an important step in order to apply the theory of algebraic specifications to development and stepwise refinement of software systems. We illustrate our notion and results by a small example implementing binary trees over arbitrary data by corresponding strings with brackets. Finally we consider the problem of 2-dimensional compatibility of parameter passing and implementation and discuss the kind of compatibility results which have been shown by other authors in the case of loose and final algebra semantics. 相似文献
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Louis-Julien Guillemette Stefan Monnier 《Electronic Notes in Theoretical Computer Science》2007,174(7):23
The use of typed intermediate languages can significantly increase the reliability of a compiler. By type-checking the code produced at each transformation stage, one can identify bugs in the compiler that would otherwise be much harder to find. We propose to take the use of types in compilation a step further by verifying that the transformation itself is type correct, in the sense that it is impossible that it produces an ill typed term given a well typed term as input.We base our approach on higher-order abstract syntax (HOAS), a representation of programs where variables in the object language are represented by meta-variables. We use a representation that accounts for the object language's type system using generalized algebraic data types (GADTs). In this way, the full binding and type structure of the object language is exposed to the host language's type system. In this setting we encode a type preservation property of a CPS conversion in Haskell's type system, using witnesses of a type correctness proof encoded in a GADT. 相似文献
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David C. Rine 《Journal of Systems Integration》1997,7(2):127-150
This paper presents a solution to an integration problem arising when copying (reusing) software components developed for one domain into software structures in a similar domain. This particular problem has not been previously addressed in the design of object-oriented languages whose intent is to enhance software reuse and software integration. Object structures are directed graphs where edges are either inheritance or client- server associations, and nodes are abstract data types. The formal logic for abstract data types used in the formal method is first-order predicate logic, and the proof system uses natural deductive logic. This is the background formal logic system, and the semantic part of each object definition uses this logic. A solution to the copyability problem is presented using the new properties of inheritance relation in copyable and out copyable, as well as client-server fan in copyable and fan out copyable. This solution to the copyability problem is presented by means of an effective method using a framework for identifying and assessing potential errors in a given object- oriented structure. Several different kinds of formal logic errors are identified which can occur during copying of object definitions represented as abstract data types into object-oriented structures. 相似文献
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This paper presents a simple and natural semantics for object-oriented languages with classes and multiple inheritance. The model, called the Formal Class model, is an intermediate level between the algebraic specification of data type, and the implementation within an object-oriented language. Our model is equipped with an operational semantics based on conditional term rewriting. One important characteristic is the use of conditional selectors. It allows one to define a type with a flat or an ordered design. In this context, we define a safe and simple type system with single dispatch and simply covariant methods. This type system is extended to some practical aspects, such as abstract classes, abstract methods, protected methods, and super methods. We describe and compare flat and ordered designs and prove that the latter is finer than the former one. We also look at multicovariant methods and show ways to fix type-checking problems using single dispatch. We describe the least pessimistic solution. Lastly, we discuss the extension of our type checking to multiple dispatch and side effects. This paper synthesizes several practical results, their proofs, and algorithms. 相似文献