Model-Mapping Approaches for Storing and Querying XML Documents in Relational Database: A Survey

Extensible Markup Language (XML), which is recommended by the World Wide Web Consortium (W3C), has rapidly become the dominant standard for data interchange and data representation on the web. At present, with the growing use of XML data on the web, the size of this type of data is increasing rapidly, and users issue more complex queries on this data. Therefore, the demand to manage this data in terms of storing and querying has elicited considerable research attention. This demand has prompted numerous researchers to propose various approaches for using relational databases to manage data because of its maturity and excellent scalability. These approaches can be categorized into: structure-mapping and model-mapping approaches. In this paper, we discuss the main characteristics and the challenge of storing XML documents in relational databases to obtain high query performance. We surveyed and compared the most cited model-mapping approaches such as Edge, XRel, XParent and XPEV. This paper presents the advantages and limitations of these approaches in this field. This Paper shows that although XPEV approach overcome on others approaches like Edge, XRel and Xparent in storage space, query response time and the influence of scalability on query performance when data sizes become bigger, it still has not resolve storing and querying XML documents in efficient way. Therefore, the paper paves the way for solutions to improve these approaches in terms of efficient storing and querying of XML documents.