A service-oriented approach to web warehousing

Data warehouses integrate and aggregate data from various sources to support decision making within an enterprise. Usually, it is assumed that data are extracted from operational databases used by the enterprise. Web warehousing relaxes this view permitting data sources to be located anywhere on the world-wide web. In this paper we even go one step further and propose that web warehousing should exploit data-intensive web services. For this we adopt the view of the recently introduced model of abstract state services (ASSs). An ASS combines a hidden database layer with an operation-equipped view layer, and can be anything from a simple function to a full-fledged Web Information System, thus provides an abstraction of web services that can be made available for use by other systems, e.g. via the web. We demonstrate how data warehouses and OLAP systems can be considered in a natural way as ASSs, i.e. selected data and functionality of a data warehouse may be made available in the form of a generalised web service, and consequently ASS composition can be used for web warehousing. In order to become workable the model of ASSs has to be extended in a way that allows services to be searched for. For this we propose federations of services together with an ontology that specifies their semantics.