Temporal Information Management Using XML

Abstract

A closer integration of XML and database systems is actively pursued by researchers and vendors because of the many practical benefits it offers. Additional special benefits can be achieved on temporal information management – an important application area that represents an unsolved challenge for relational databases [1]. Indeed, XML data model and query languages support:

• Temporally grouped representations that have long been recognized as a natural data model for historical information [2], and

• Turing-complete query languages, such as XQuery [3], where all the constructs needed for temporal queries can be introduced as user-defined libraries, without requiring extensions to existing standards.

By contrast, the flat relational tables of traditional DBMSs are not well-suited for temporally grouped representations [4]; moreover, significant extensions are required to support temporal information in SQL and, in the past, they were poorly received by SQL standard committees.

We will show that (i) XML hierarchical structure can naturally represent the history of databases and XML documents via temporally-grouped data models, and (ii) powerful temporal queries can be expressed in XQuery without requiring any extension to current standards. This approach is quite general and, in addition to the evolution history of databases, it can be used to support the version history of XML documents for transaction-time, valid-time, and bitemporal chronicles [5]. We will demo the queries discussed in [5] and show that this approach leads to simple programming environments that are fully-integrated with current XML tools and commercial DBMSs.