Standard precedence rules display the target dimension if the
trigger dimension value or its descendants are in the navigation state. Leaf
precedence rules display the target dimension only after descendants of the
trigger dimension value have been selected.
There are two types of precedence rules, standard
and leaf. The types differ in how the trigger dimension value is interpreted.
- For the standard type, if
the dimension value specified as the trigger, or any of its descendents, are in
the navigation state, then the target dimension is displayed.
- For the leaf type, only leaf
dimension values (dimension values with no children) that are descendents of
the specified trigger dimension value cause the target dimension to be
displayed. The presence of the specified trigger dimension value in the
navigation state does not cause the target dimension to appear. Hence, a leaf
precedence rule requires that the trigger dimension value has children.
A standard precedence rule is indicated by this icon
in the Precedences Rules view. A leaf precedence rule is
indicated by this icon
).
Standard Rule Example
In this standard rule example, we
have a
Color dimension with a child dimension value named
blue. We can construct a standard precedence rule
with
blue as the trigger dimension value and the
dimension
Shades of Blue as the target. Once the user drills
into
Color and selects
blue, the target dimension
Shades of Blue is displayed in the user interface.
Leaf Rule Example
For leaf type rules, we'll examine a hierarchical dimension named
Country and a second dimension named State/Province. The Country dimension
looks like this:
- Country
- North America
- Canada
- Mexico
- United States
- Europe
- England
- Spain
- Italy
Logically, a user should choose a country before choosing a state or
province. We can use a leaf precedence rule to suppress the display of the
State/Province dimension until a leaf value in the Country dimension (an actual
country as opposed to a continent) has been selected. To achieve this, a leaf
precedence rule is constructed with the Country dimension root as the trigger
and the State/Province dimension as the target. If the user drills into Country
and selects an intermediate child dimension value (North America or Europe),
the target dimension State/Province is not displayed. However, once the user
has selected a leaf value from the Country dimension (United States, Canada,
Mexico, England, Spain, or Italy) the State/Province dimension appears.