The MDEX Engine supports two types of multiselect dimensions.

The default behavior of the Oracle Commerce MDEX Engine permits only a single dimension value from a dimension to be added to the navigation state. This type of dimension is called a single-select dimension.

By default, after a user selects a leaf refinement from any single-select dimension, that dimension is removed from the list of dimensions available for refinement in the query results. For example, after selecting "Apple" from the Flavors dimension, the Flavors dimension is removed from the navigation controls.

However, sometimes it is useful to enable the user to select more than one dimension value from a dimension. For example, you can give a user the ability to show wines that have a flavor of "Apple" and "Apricot". This function is accomplished by tagging the dimension as a multiselect dimension. The MDEX Engine provides support for two types of multiselect dimensions that apply Boolean logic to the dimension values selected:

The multiselect feature is only fully supported for flat dimensions (that is, dimensions that do not contain hierarchy). In other words, multiselect-OR queries are restricted to leaf dimension values. In a flat dimension, all possible refinements are leaf dimension values, so no extra configuration is necessary. In a hierarchical dimension, you must configure all non-leaf dimension values to be inert (non-navigable) to prevent them from appearing in the navigation query.