A grouping of related characteristics under a single generic term. If the dimension contains a characteristic whose value already uniquely determines the values of all other characteristics from a business perspective, the dimension is named after this characteristic.
The customer dimension could be made up of the customer number, the customer group and the levels of the customer hierarchy for example.
The sales dimension could contain the characteristics ‘sales person’, ‘sales group’ and ‘sales office’.
The time dimension could have the characteristics ‘day’ (in the form YYYYMMDD), ‘week’ (in the form YYYY.WW), ‘month’ (in the form YYYY.MM), ‘year’ (in the form YYYY) and ‘period’ (in the form YYYY.PPP).
When defining an InfoCube, characteristics for dimensions are grouped together so that they can be stored in a star schema table (dimension table). This can be based on the grouping from a business perspective mentioned above. Using a basic foreign key dependency, dimensions are linked to one of the key fields in the fact table.
More information: Enhanced Star Schema
When you create an InfoCube, the dimensions data package, time and unit are pre-defined for you. The data package dimension contains technical characteristics. Units are automatically assigned to the corresponding dimensions. You have to assign time characteristics manually. When you activate the InfoCube, only dimensions containing InfoObjects are activated.
From a technical point of view, multiple characteristic values are mapped to a single abstract dimension key (DIM ID). The values in the fact table are based on this key. The characteristics chosen for an InfoCube are divided up among InfoCube-specific dimensions when creating the InfoCube.
For details about specific cases that can arise when defining dimensions, see:
Line Item and High Cardinality