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张霞, 孙雨, 刘积仁
,-0001,():
-1年11月30日
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
DBMS optimizing hints query optimization
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【期刊论文】MOPOM: AN OBJECT-ORIENTED MULTIMEDIA DATA PRESENTATION MODEL
张霞, XIA ZHANG, JIREN UU and HUATIAN LI
Advances in Modelling & Analysis, B, AM SE Press, Vol. 31, No2, 1994, pp. 47-56,-0001,():
-1年11月30日
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.
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张霞, Cheng Wanjun, Zhang Xia, Liu Jiren
,-0001,():
-1年11月30日
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.
Data security,, Security model,, Multilevel security,, Access control,, Security policy
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张霞
,-0001,():
-1年11月30日
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。
多媒体数据库,, 数据模型,, 表达模型., 时空编组,, Petri网.,
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张霞, 刘积仁, 都军
,-0001,():
-1年11月30日
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。
多媒体,, 分布式多媒体,, 多媒体数据库,, 计算机支持群体协同工作
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