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.