In the Business Model and Mapping layer, a dimension object represents a hierarchical organization of logical columns (attributes).
One or more logical dimension tables can be associated with at most one dimension object.
Common dimensions might be time periods, products, markets, customers, suppliers, promotion conditions, raw materials, manufacturing plants, transportation methods, media types, and time of day. Note that dimensions exist in the Business Model and Mapping (logical) layer and in the Presentation layer.
In each dimension, you organize logical columns into the structure of the hierarchy. This structure represents the organization rules and reporting needs required by your business. It also provide the metadata that the Oracle BI Server uses to drill into and across dimensions to get more detailed views of the data.
There are two types of logical dimensions: dimensions with level-based hierarchies (structure hierarchies), and dimensions with parent-child hierarchies (value hierarchies). Level-based hierarchies are those in which members are of several types, and members of the same type occur only at a single level. In parent-child hierarchies, members all have the same type. Oracle Business Intelligence also supports a special type of level-based dimension, called a time dimension, that provides special functionality for modeling time series data.
Because dimensions for multidimensional data sources are defined in the source, they do not require as much work compared with dimensions in other data sources. For example, you do not create dimension level keys. A dimension is specific to a particular multidimensional data source (it cannot be used by more than one) and cannot be created and manipulated individually. Additionally, each cube in the data source should have at least one dimension and one measure in the Business Model and Mapping layer.
You can expose logical dimensions to Oracle BI Answers users by creating presentation hierarchy objects that are based on particular logical dimensions. Creating hierarchies in the Presentation layer enables users to create hierarchy-based queries, see Working with Presentation Hierarchies and Levels.
Note that you can also expose dimension hierarchies by adding one or more columns from each hierarchy level to a subject area in the Presentation layer. Oracle BI Answers supports drill-down on these hierarchical columns.