The term OLAP was first introduced by E. F. Codd, who pioneered Relational Database Management Systems (RDBMS). Below are the twelve rules defined by Codd that OLAP technology must support.
| Multidimensional conceptual view |
Supports EIS (Executive Information System) slice and dice operations and is usually required in financial modeling. |
Transparency |
Is part of an open system that supports heterogeneous data sources. Furthermore, the end user should not be concerned about the details of data access or conversions. |
Accessibility |
Presents the user with a single logical schema of the data. OLAP engines act as middleware, sitting between heterogeneous data sources and an OLAP front-end. |
Consistent reporting performance |
Performance should not degrade as the number of dimensions in the model increases. |
Client/server architecture |
Requires open, modular systems. Not only the product should be client/server but the server component of an OLAP product should allow that various clients could be attached with minimum effort and programming for integration. |
Generic dimensionality |
Not limited to 3-D and not biased toward any particular dimension. A function applied to one dimension should also be able to be applied to another. |
Dynamic sparse-matrix handling |
Related both to the idea of nulls in relational databases and to the notion of compressing large files, a sparse matrix is one in which not every cell contains data. OLAP systems should accommodate varying storage and data-handling options. |
Multiuser support |
Supports multiple concurrent users, including their individual views or slices of a common database. |
Unrestricted cross-dimensional operations |
All dimensions are created equal, so all forms of calculation must be allowed across all dimensions, not just the measures dimension. |
Intuitive data manipulation |
Users shouldn't have to use menus or perform complex multiple step operations when an intuitive drag and drop action will do. |
Flexible reporting |
Users should be able to print just what they need, and any changes to the underlying model should be automatically reflected in reports. |
Unlimited dimensional and aggregation levels |
Supports at least 15, and preferably 20, dimensions. |
