EHDM的DL封装机制及在Z39.50协议上的应用

DL Wrapper Mechanism of EHDM with Applications on Z39.50

Z39.50被广泛应用在异构数据源的检索中,由于数据源的动态性和自治性,无法准确获得其语义,很难建立Z39.50与数据源的映射关系,为进行准确的信息检索操作,提出扩展超图数据模型(EHDM),对EHDM进行层次抽象,以EHDM的两类节点和边作为Z39.50协议的访问点,通过在EHDM和Z39.50之间建立DL层,将DL系统的概念、导出概念分别映射到Z39.50协议包装器上,解决Z39.50协议查询对结构化数据源支持不好、出现错误查询结果集等问题,定义类DataSpace的三层结构实现根据需求进行集成的"量入为出"的数据集成策略。

Z39.50 is widely used for searching and retrieving information spread over a number of heterogeneous sources, but it is hard to construct the mapping relationships between Z39.50 and the data sources, since the semantics of the dynamic and autonomy data sources cannot be exactly derived so as to achieve an exact information retrieval operation. This paper proposes the extend hyper graph data model based on HDM, which can be abstracted into levels, taking two kinds of nodes and edges of EHDM as access points of Z39.50. It can solve the problems of badly supporting of querying on struetured data sources and query failures by constructing the DL layer between EHDM and Z39.50, in which the concepts and derived concepts are mapped onto Z39.50 wrappers. Thus, defining three layers structure as in dataspaee systems can realize the data integration strategy named ＂integrate when needed＂.