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2.2.5.4 OLAP Data Model

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This section provides background information about the underlying data model for OLAP entities.

The principal unit of scope is an OLAP cube. See section 2.2.8 for information about how an OLAP cube is accessed. Items within an OLAP cube can be addressed by an MDX unique name string. Within an OLAP cube, there are OLAP hierarchies, OLAP measures and OLAP named sets.

An OLAP hierarchy consists of one or more OLAP levels and OLAP member properties. An OLAP level consists of one or more OLAP members. An OLAP member is an atomic unit of data, for example customer "Jim Smith", or a grouping of data, for example "customers in the city of Chicago". OLAP levels contain OLAP members of similar type within an OLAP hierarchy. OLAP members can have parent and child members in OLAP levels above and below them, for example "Jim Smith" might be a child of "customers in the city of Chicago". An OLAP member property can be associated with a single OLAP level or all OLAP levels of an OLAP hierarchy, for example a "Mayor" OLAP member property might be associated with a "City" OLAP level.

An OLAP tuple is a way of combining multiple OLAP members to reference a particular point in an OLAP cube, for example "customers in the city of Chicago" and "2008" references data in the OLAP cube corresponding to the year 2008 and customers in Chicago.

An OLAP measure is a value that is available in the OLAP cube. Usually it is numeric, "Sales" and "Head Count" are typical examples of OLAP measures. An OLAP measure is an OLAP member in a measures OLAP hierarchy. For a PivotTable view (section 2.2.5.3), OLAP measures are stored differently from other OLAP members in this file format.

An OLAP tuple including an OLAP measure can be used to get a value, for example "customers in the city of Chicago", "2008" and "sales" might reference the value $659,000.

An OLAP named set is a collection of OLAP tuples. OLAP named sets are typically used for specific analytical needs that require custom logic, for example an OLAP named set might be defined as the OLAP tuples corresponding to "the top 10 customers by month and sales".