Design and implementation of a Correspondence Database System

In recent years, the increase in the use of XML makes semi-structured data more and more important. However, XML is not very suitable for the data which has network structure because its basic structure is tree. In this paper, it is proposed that a Correspondence Data Model for semistructured data which has network structure and a query language GRQL (GRaph Query Language) of the database system based on this model. Examples of query in GRQL are also shown. Moreover an implementation of the prototype system is introduced. The traditional database systems are inappropriate to semi-structured data because the structure of semi-structured data is frequently not rigid and not complete. Most semi-structured data are considered to be network structure. Therefore it is desirable that the data models have good compatibility with network structure for semi-structured database systems. In Correspondence Data Model, the data is represented as a group of labeled directed graphs. The operations in Correspondence Algebra make systematic data manipulations possible. GRQL enables users to describe queries in a way of graph scanning.