Cardinality is combined with dimensions to control how queries are generated so that you can
• prevent double-counting
• automatically resolve loop joins
• enable cross-fact querying for reporting and analysis
You can create model dimensions and data source dimensions. Model dimensions are built on a foundation of query subjects that use determinants and relationships with cardinality. Data source dimensions contain their own SQL and use hierarchy and level information as well as relationships with cardinality to define query granularity.
Cardinality drives query behavior by allowing rules to be applied regarding the granularity of data that is returned by an individual object and the consequence of joins between objects. The cardinality specified in the relationship between query subjects or dimensions determines how and when Cognos 8 generates stitched queries. Stitched queries are needed for multiple-fact querying across conformed dimensions and across different levels of granularity.
