Native xml databases vs. relational databases in dealing with xml documents

摘要

When dealing with data-centric XML documents, it is possible to convert XML documents into a relational database, which can then be queried using SQL. Such relational databases are called {it XML-enabled databases}. On the other hand, the best choice for storing, updating and retrieving document-centric XML documents is usually a {it native XML database (NXD)}. NXDs store XML documents as logical units, and retrieve documents using specific query languages such as XPath or XQuery. This paper presents different approaches to accessing XML documents from relational databases, as well as from native XML databases. They will be compared based on how general they are in dealing with different types of XML documents and how expressive in stating requests for data, especially recursive queries. Two examples of different types of XML documents are presented. The first one is a part explosion problem as a data-centric example. The second one is a large, highly hierarchical XML document - Serbian language wordnet, a lexical-semantic network, as a document-centric example.