Dimension Updates and Hierarchy Maintenance in OLAP Database

OLAP systems are designed by implementing the multidimensional data model. Data facts in the model are viewed as points in a space of application-related dimensions. Usually they are organized in levels which conform to a hierarchy. OLAP database facilitates a special class of queries performed on large collection of integrated data that support the decision making process. Central issue in data analysis for decision making is aggregation. The hierarchical structure of dimensions enables the definition of different levels of aggregation. Changes in the data sources or user requirements must be reflected by updating some dimensions. Dimension updates modifying the structure of a dimension scheme or its instances are considered. Implementation plans for dimension updates in a proposed relational scheme of the OLAP database are designed. Algorithm for maintaining pre-computed aggregations as a result of updates is proposed.