Multi-select attributes gives the ability to the user to select more than value at a time.
See the navigation Property system-navigation_Select.
This property can takes this values:
No multi-select feature.
The refinement will perform a “and” operation on the search terms selected.
Multi-assign attributes are required to support ‘multi-select And’ behaviour.
The refinement will perform a “or” operation on the search terms selected.
Multi-select AND or OR dimensions can have more than one dimension value in the Navigation pane (parameter), but cannot be hierarchical.
If one of the descriptors is a hierarchical ancestor of another, the MDEX Engine consolidates descriptors into single dimensions. The only exception to this is when a dimension is marked for multi-select. When a dimension is marked for “multi-select and” or “multi-select or”, the consolidation is not made and each descriptor gets its own dimension object.
Knowledge of the multi-select settings for a dimension allows the application to present a tailored user interface for selecting refinements from that dimension (for example, radio buttons for a single select dimension versus check boxes for a dimension enabled for multi-select OR).