A definition for "Dimension" in Analysis Services / OLAP
Posted on 2009-02-24
In the Glosary of the BOLs of the SQL Server 2005 you can find the following definition for "Dimension" in Analysis Services:
"A structural attribute of a cube, which is an organized hierarchy of categories (levels) that describe data in the fact table. These categories typically describe a similar set of members upon which the user wants to base an analysis. For example, a geography dimension might include levels for Country, Region, State or Province, and City."
I have a doubt with regard of this: What is really a Dimension?
If you take the first words ("A structural attribute of a cube") a dimension seems to be just an attribute, in concrete the key attribute, it is, the attribute related to the PK in the dimesion table.
But if you think about the following words ("which is an organized hierarchy of categories (levels)..."), it seems that a dimension comprises the whole set of attributes derived from the dimension table.
I think that clear defiitions are very important for any discipline, and that there are not good unified ones for OLAP. What do you think?