A Comparison of Element-based and Path-based Approaches to Indexing XML Data

The mark-up language XML (Extensible Mark-up Language) is recently understood as a new approach to data modeling. A well-formed XML document or a set of documents is an XML database and the associated DTD or schema specified in the language XML Schema is its database schema. Implementation of a system enabling us to store and query XML documents efficiently (so called native XML databases) requires a development of new techniques that make it possible to index an XML document in a way that provides an efficient evaluation of a user query. Most of XML query languages are based on the language XPath and use a form of path expressions for composing more general queries. In the paper we compare element-based and path-based approaches to indexing XML data. In the case of element-based approaches query is evaluated step by step. Each step produces a lot of elements which may be refused in the next evaluation step. In the paper we show that the previously published multi-dimensional path-based approach overcomes conventional element-based approaches.