A hierarchy is a
cascaded series of many-to-one relationships and consists of different levels.
Example, a region
hierarchy is defined with the levels Region, State, and City
Types of Hierarchies
1. Balanced hierarchy
2. Unbalanced hierarchy
3. Ragged hierarchy
1. Balanced hierarchy
A balanced hierarchy is
one in which all of the dimension branches have the same number of levels. In
other words, the branches have a consistent depth. The logical parent of a
level is directly above it.
A balanced hierarchy can
represent a date where the meaning and depth of each level, such as Year,
Quarter, and Month, are consistent.
2. Unbalanced hierarchy
A hierarchy is
unbalanced if it has dimension branches containing varying numbers of levels.
An unbalanced hierarchy
has levels that have a consistent parent-child relationship, but have a
logically inconsistent level. The hierarchy branches also can have inconsistent
depths. An unbalanced hierarchy can represent an organization chart.
3. Ragged hierarchy
A ragged dimension
contains at least one member whose parent belongs to a hierarchy that is more
than one level above the child. Ragged dimensions, therefore, contain branches
with varying depths.
A ragged hierarchy is
one in which each level has a consistent meaning, but the branches have
inconsistent depths.
A ragged hierarchy can
represent a geographic hierarchy in which the meaning of each level, such as
city or country, is used consistently, but the depth of the hierarchy varies.
