Authors: Georgia Garani; George K. Adam; Dimitrios Ventzas
Addresses: Department of Computer Science and Engineering, Technological Educational Institute of Thessaly, 41110 Larissa, Greece ' Department of Computer Science and Engineering, Technological Educational Institute of Thessaly, 41110 Larissa, Greece ' Department of Computer Science and Engineering, Technological Educational Institute of Thessaly, 41110 Larissa, Greece
Abstract: Temporal data warehouses (TDWs) have been developed for the management of time-varying data in dimensions. This paper presents a new approach for the logical modelling of TDWs. The novel design is based on the integration of two schemata, the star schema and the snowflake schema, to the temporal starnest schema. Time in the temporal starnest schema is not treated as another dimension but as time attributes in every temporal dimension, i.e., dimension tables dependent on time. Time manipulation functions for the treatment of time attributes are provided in the query language. The temporal starnest schema proposed in this paper expresses naturally hierarchy levels by the clustering of data in nested tables, with resulting description of aggregation levels for a dimension in a natural way. The proposed extension is applied to a TDW for accident monitoring in crossroads where the expressive power of the model is exemplified with several temporal queries expressed in a suitable extension of SQL standard.
Keywords: temporal data warehouses; TDW; temporal databases; valid time; logical modelling; starnest schema; nested relations; temporal nested dimension; hierarchy; transaction times; temporal queries; data management; time-varying data; accident monitoring; crossroads; road traffic accidents.
International Journal of Data Mining, Modelling and Management, 2016 Vol.8 No.2, pp.144 - 159
Received: 03 May 2014
Accepted: 08 Aug 2014
Published online: 21 Jun 2016 *