本文提出一种多媒体数据表达模型：演员模型，该模型建立在多媒体数据库概念模型基础之上，基于库所一时同Petri网，描述多媒体对象之间的时态关系，同时引入与变迁相关联的场景表达式，描述多媒体对象之间的空间关系，从而模拟多媒体数据的时空编组，文中形式化地定义了演员模型的抽象模型和实现模型。提出多媒庠对象的表达算法以及多媒体数据库的查询模型。

The proposed BLP-i is based on the classical Bell-LaPadula model, and it redefines new object datatype, object hierarchical structure, referential relation, etc. These make integrity properties become inherent properties of the model. The model uses the view function to expresses the axiom and the rules of operation.To reduce the need of trusted codes and prevent covert channels,the model restricts that transactions in system are single-level and restricts object's some behaviors. By those ways, the proposed mode can preserve data integrity defined in the model while it's multilevel secure.

伴随着“信息高速公路”的兴起，分市式多媒体这一综合的跨学科的研究领域越来越受到人们的重视。如何认识分市式多媒体技术，以及如何把握其未来的发晨方向对于从事这一领域工怍的科研开发人员是十分必要的。本文从计算机学科的角度出发。对分布式多媒体技术的产生、分布式多媒体的通信平台、分布式多媒体通信协议、分布式多媒体数据库及其应用等方面做了概要的阐述。并对导一部分的发展做了展望。

This papar explains an object-odiented virual integration approach of heterogeneous distributed databases. which is used in CIMBASE+. We introuce briefly the basic concepts and features of the global data. model OSAM* and global data languagc 0SDL of CIMBASE+, explain the virtual schema integration, approach. and describe the mampulation process of the virtual integrated database.

This paper deals with the multimedia data presentation model, which is one of the palticular problems of multimedia databmm systems. First, the characteristics of mul-timedia data are discussed. Secondly. the existing multimedia data models are analysed. And then the method of concept and presentation modelling is explained, and the schema architecture of a multimedia database system is described. Finally, the problem of spatio-temporal composition of multimedia objects is discussed. and a multimedia data presentation model, namely, Multimedia Object Play-Out Model (MOPOM). is defined.

This paper deals with the data model for multimesha objects. which is one of the crucial problems ofmultimexha database systems First. the characteristics of multimesha data are discussed. the existing multimedia data models are mmlyzed and the schema architecture of a multimesha database system Is presented. which is based on cncept and presentation modeling Secondly, a fonnal concept model for inulttmedia objects is defined Finally. the problem of spatio-temporal composition of multimedia objects is discussed. and a presentation model for multimedia objects is denfined.

The existing heterogeneous distributed database management systems (HDVBMSs) which are businss-oiiented will not be able to adequnte for many new and developing information processing applications. The important objective of these applications include the processing of complex objects and intelligence. Our approach is integrating logic and object paredigm to provide knowledge representation and infererence echanism in HDDBMS. This paper decribes the knowledge representetion in object-oriented heterogeneous distributed database system with semuntic association--OHDDB-DGI, presents the method of processing consltaints and rules in the global language OSAL which is Object-orientcd and of Semantic Association with bogic. and explains briefly the peculiarities of processjng inheritance and recursive inference.

安全策略模型是安全可信系统的基础。Bell-LaPadula模型是多级安全系统中广泛应用的安全策略模型，但它缺乏针对数据模型的完整性和一致性规则。以该模型为基础，针对数据库系统的数据模型，提出了一个以扩展客体层次结构为基础的安全策略模型。模型通过扩展客体层次结构使完整性成为模型的内在属性，并引入或重新定义了客体域、扩展安全公理和操作规则.模型更加适应多级安全数据库系统的要求，增强了策略模型与系统规格和高层模型的一致性。普遍性和通用性安全模型的扩展和增强，特别是安全性以外的特性的引入是安全策略模型向实际系统模型转化的必要步骤。

本文形式化地提出了一种适用于多媒体对象的概念模型OMCOM文中首先分析多了媒体数据模拟的特殊性，探讨了现有的多媒体数据模型的不足，从而提出了把多媒体数据模拟划分为慨念与表达两级模拟的思想概念级模拟多媒体对象的内容与结构；表达级模拟其表达，包括多媒体对象之间的时态关系和空间关系。OMCOM就是一种用于实现概念级模拟的模型。然后根据多媒体概念模拟的需求，形式化地定义了OMCOM的各个构成要素。最后根据OMCOM实例的格性质，建立了多媒体对象在概念级的运算体系——对象代数，形式化地定义了其中的各种运算以及对象代数表达式。

Currently, the popular DBMS products, for example Oracle、SQL Server、DB2、OpenBASE etc, offer highly efficient query function and complicated optimizing process. However in some circumstances, these successful DBMS query optimizer can not always make an optimal execution plan, even interfere performance. It is necessary to introduce the query hints as an query optimizing auxiliary measure. This paper analyzes the motivation and merit of the query hints, and the effection on the performance, finally describes the hints implementation in the OpenBASE