Hierarchical dimensions

A hierarchical dimension is defined by its hierarchies. A hierarchy is defined by dimension items (groups and members) and relationships. This gives you the ability to custom-build complex information structures that mirror specific aspects of your business. Unlike flat dimensions, which can be compared to reference sheets, hierarchical dimensions most closely resemble a standard directory structure like those found in computers. The foundation for building these structures lies in two core concepts:

• Using groups and membership to subdivide the collection of members.
• Using the ranking structure of hierarchies to categorize members.

This section illustrates these concepts and how to use the wizard to import database structure into hierarchical dimensions.

Unlike flat dimensions, hierarchical dimensions contain two types of items: groups and members. Groups introduce the ability to form one of the two relationship types that define a hierarchical dimension: membership.

With the ability to form membership, a group is like a compartment within the dimension that serves to group the dimension's members. In the example, World, Continent, City, and Country are used as the groups to divide the existing dimension's members. Without applying the relationship of membership, the new group items only add to the existing bulk. After membership is applied, the importance of groups as a tool to organize becomes clear.

A hierarchy is a ranked structure with a top level and subordinate levels. The top level has one member or only a few members. The subordinate levels are specialized forms of the item above it. The lowest level, called the base level, is the most specialized form of the top member.

This diagram illustrates what a hierarchical structure of the world's group items might look like. All the subordinate levels become increasingly specialized aspects of the top level, World, as you move down to the base level, City. For example, a country can have many cities, but a city is typically associated with only one country. City is a more specialized form of World than Country is.

The relationship between levels is referred to as a parent/child relationship. In the diagram below, Country is the child of Continent and the parent of City. This example depicts the hierarchy of groups within a dimension. However, a dimension's members have their own hierarchy as shown here.