Multi-select refinements and the user interface

If an attribute is configured as multi-and or multi-or, this affects the way Endeca Server calculates the refinements for such attributes, and therefore, has implications for the display of such refinements in the user interface.

The default Guided Navigation behavior of Endeca Server is to allow users to add only a single value from an attribute to the navigation state. This means that when users select a refinement from an attribute (by clicking it in the user interface, in the list of suggested refinements), that attribute is removed from the list of suggested refinements available for future refinement in the query results. For example, after selecting "Apple" from the Flavors attribute, the Flavors attribute is removed from the user interface's navigation controls. However, sometimes it is useful at navigation time to allow the user to select more than one value from an attribute. For example, the user interface can provide a user with the ability to show wines that have both "Apple" and "Apricot" values from the "Flavor" attribute.

To summarize, even though the fact that an attribute is tagged as multi-select is transparent to the front-end application's developer, the behavior of multi-select attributes may require changes in the user interface. Once an attribute is tagged as multi-select, the semantics of how Endeca Server interprets navigation queries and returns available refinements changes. After tagging an attribute as multi-select, Endeca Server allows multiple attribute values from the same attribute to be added to the navigation state. Endeca Server behaves differently for the two types of multi-select attributes:

A refinement for a multi-and attribute. Endeca Server treats the list of attribute values selected from a multi-and attribute as a Boolean AND operation. That is, Endeca Server will return all records that satisfy the Boolean AND of all the attribute values selected from an attribute that is multi-and. For example, it will return all records that have been tagged with "Apple" AND "Apricot". If the user continues the refinement process by clicking one of the suggested refinements, Endeca Server will also continue to return refinements for a multi-and attribute. The list of available refinements will be the set of attribute values that have not been chosen, and are still valid refinements for the results.
multi-or refinement. If the navigation state contains multiple values from a multi-or refinement, then all of the records in that state contain at least one of the selected values. A multi-or attribute is analogous to a multi-and attribute, except that a Boolean OR operation is performed instead (that is, all records that have been tagged with "Apple" OR "Apricot" are returned). Endeca Server will always return all attribute values for a multi-or attribute that have not already been selected – this means that the set of suggested refinements in the user interface does not correlate to the set of remaining records. Also note that as more multi-or attribute values are added to the navigation state, the set of record results gets larger instead of smaller, because adding more terms to an OR expands the set of results that satisfy the query.
single configures the attribute as a single-select attribute. This means that only one value can be selected for an attribute at a time. This is the default.