Issues of object-relational view design in data warehousing environment

Data warehouses contain a vast amount of data, often from different sources. In order to support complex queries of various decision support systems, we need to store materialized views of data. These views represent integrated data based on complex aggregate queries, and should be available consistently and instantaneously, which would not be possible if those queries had to be invoked each time on the varied data sources. Conventional approaches have been based on the relational model where materialized views are stored as tables in the warehouse. This also means that semantics of the data warehouse structure are hidden. Using object-oriented methodology, we can explicitly represent the semantics and reuse view (class) definitions based on the ISA hierarchy and the class composition hierarchies, thereby resulting in a more efficient view mechanism. This paper deals with the issues concerned with providing an object-relational view (ORV) mechanism for the data warehouse. Primary issues are: providing object views for the relational data and for aggregate/summary data. These include translating the relational data structures into a class hierarchy, defining class structures for the summary views, supporting object ids for object instances of the views (classes) generated handling those classes with respect to maintenance and providing links to other classes in the hierarchy, and accessing and querying these view classes.