This section discusses precedence rules and explains their performance impact.
Precedence rules let you limit the presentation of certain Guided Navigation dimensions only to specified navigation states.
You configure precedence rules in Developer Studio.
Each precedence rule lets you identify a trigger dimension value and a target dimension, and presents the target dimension for Guided Navigation only in those query contexts in which:
For example, suppose that an application includes a precedence rule linking the trigger dimension value “Part Category > Passives > Resistors” to a target dimension “Resistance”, which might contain refinements such as “10 ohms” and “22 ohms”.
In a navigation query where, for example, the user performs a search matching records tagged with a variety of values from “Part Category” including “Resistors” and other values, and where the user does not explicitly or implicitly select the dimension value “Part Category > Passives > Resistors”, the “Resistance” dimension is not returned for Guided Navigation.
This prevents the presentation of a contextually irrelevant navigation dimension to the user. Before the user has indicated some interest in resistors, presenting “Resistance” navigation choices may be unexpected, clutter the presentation of more relevant navigation choices, and detract from the overall experience.
If the user subsequently selects the “Part Category > Passives > Resistors” dimension value as a refinement, the “Resistance” dimension is presented for Guided Navigation (assuming that there are valid, available navigation refinements available for “Resistance”). Similarly, if the user performs a search that triggered “Part Category > Passives > Resistors” as an implicit refinement, for example if the user performed a text search for a manufacturer who only makes resistors, the “Resistance” dimension is returned for navigation.
This unique behavior provided by the MDEX Engine allows the contextual presentation of appropriate navigation dimensions to be more automatic and adaptive, as the front-end application need not be aware that the user's search has implied “Part Category > Passives > Resistors” for the “Resistance” dimension to be presented automatically as a navigation dimension.
