Dimensions are the building blocks of OLAP tools like TM1. This underscores the need to have correct dimensions for the specific purpose intended.
Dimensions can be classified in the following categories.
Based on Functionality:
Master / Reporting Dimensions
- The master dimensions are used to create other dimensions, which are mathematical subsets of the master dimension
E.G. a department hierarchy with all departments (active and inactive) is a master dimension.
A dimension with active departments only can be derived from the master dimension and used for budget.
- Master dimensions can help reporting since master dimensions can continue to have inactive elements.
- Master dimensions can store time based snapshots
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E.G. Say the hierarchy appearance has changed over years, the master dimension can store multiple hierarchies – one for each year.
- Master dimensions can also help in security management of the entire environment. Security can be set in a cube with the master dimension and propagated to other dimensions.
- The cubes with master dimensions can have minimal number of rules. This would make it easy to archive data.
- Master dimensions are a good idea, even if, reporting is not a part of the environment.
Budget Dimensions
- Budget dimensions are dimensions that store relatively much lesser number of elements, help in creating budgeting cubes and apply complex logic that can change year over year.
- The number of elements in a cube is relatively less with only active elements required.
Hybrid Dimensions
- Certain dimensions can be easily used across the Reporting and Budget environments
- Hybrid dimensions also signify cross usage of dimensions across their type (detailed below) i.e. a Measures dimension combined with time.
Based on Type:
- Departments or a variation (Products. Divisions etc.)
- Accounts (Chart of Accounts or a subset)
- Versions/ Scenario
- Time
- Measures
- Supporting Dimensions
The types of dimensions used and the number of dimensions for each type depend on needs of an environment.
While collecting requirements, it is necessary to determine how many cubes and dimensions will be required.
However, to determine the number of dimensions, it is necessary to evaluate the behavior of data across the first four categories of dimensions – Departments, Accounts, Versions and Time.
All cubes storing budget or reporting data must have a measures dimension.
A Global Assumption Cube couldhave Time (Year) dimension to support storing the assumptions across multiple years.
More about dimensions in next issue…
