Member Sets

Member sets are used to group data items that are logically related for various actions, such as drill actions, zero suppression, and ranking. They can be defined as a flat list or as a tree structure in which member sets in the same parent chain are considered related.

For example, for drill operations, a member set defines the set of items that can potentially change when a given item in the set is drilled on. The values of other items in the query or even those in the same hierarchy are preserved when any item in this set is drilled on. Usually, a member set references items that have logical roles in a drill action, such as a detail, a summary of the detail, or a parent of the detail. A single data item can belong to only one member set.

If you do not define member sets for items, the IBM® Cognos® Analytics server associates items into default member sets and behaviors using simple dimension rules on item expressions. You can override the behavior for a particular item while other items continue to use the default.

When you define a member set, you must explicitly define behaviors for each item in the set. Items in the set that have no behaviors have their values preserved.

Drill behaviors always act from a root member set. This means that when an item is drilled on, the root member of its member set is found and all items from the root down are processed. Although calculations and aggregates are not directly related by hierarchy, they respond because of their dependence on the items upon which they are based.