A web-based architecture for Temporal OLAP. (18th August 2008)

• Record Type: Journal Article
• Authors: Vaisman, Alejandro A.; Izquierdo, Adrian; Ktenas, Marcelo
• Is Part Of: International journal of Web engineering and technology. Volume 4:Number 4(2008)
• Page Start: 465
• Page End: 494
• Publication Date: 2008-08-18
• Subjects: temporal databases -- temporal OLAP -- TOLAP -- web services -- dimension updates -- SOAP -- XML -- query performance -- online analytical processing; World Wide Web -- Periodicals; Web site development -- Periodicals; Application software -- Development -- Periodicals; 006.7
• Languages: English
• ISSNs: 1476-1289

Abstract

Commercial OLAP systems usually consider OLAP dimensions as static entities. In practice, dimension updates are often necessary in order to adapt the multidimensional database to changing requirements. Query languages are then needed to retrieve historical information from a data warehouse. Although many proposals addressing temporal OLAP exist, none supports full operation over the World Wide Web. After introducing a temporal data model supporting historical dimensions and fact table versioning, we present a three-tier architecture based on web services, SOAP and XML, allowing efficient querying over the web. In this architecture, XML metadata is stored at the application server in the form of XML documents containing the data warehouse structure. This allows addressing most of the requests (navigation through time, updates and queries) without accessing the data warehouse. In the second part of the paper, we present TOLAP-QL, an SQL-like temporal query language. We describe the syntax and semantics of the language, a sequel of its logic-based predecessor, TOLAP. We study query optimisation in temporal OLAP, and introduce a technique based on materialisation of historical views. Last, but not least, we present a system implementation, and a real-world case study, that shows that our proposal achieves good query performance for OLAP queries over large historical databases in a web environment.