The behavior of multiselect dimensions may require changes in the UI.

The fact that a dimension is tagged as multiselect should be transparent to the Presentation API developer. There is no special Presentation API development required to enable multiselect dimensions. There are no URL Query Parameters or API objects that are specific to multiselect dimensions.

However, the semantics of how the MDEX Engine interprets navigation queries and returns available refinements changes once a dimension is tagged as multiselect. After tagging a dimension as multiselect, the MDEX Engine will then enable multiple dimension values from the same dimension to be added to the navigation state.

The MDEX Engine behaves differently for the two types of multiselect dimensions:

A comparison of single-select and multiselect-OR dimensions shows the difference in the generation of standard and implicit refinements. The table shows these differences using a simplified case with only one selected dimension value:

Single-select dimension

Multiselect-OR dimension

Children of the current dimension value are potential refinements because selecting one could reduce your record set. Those that would change your record set if selected are standard refinements, while those that would not change your record set if selected are implicit refinements.

Children of the selected dimension value are not potential refinements, because selecting one would not expand the record set. Therefore, they are the implicit selections.

Ancestors of the dimension value are not potential refinements, because selecting one would not reduce the record set. They are the implicit selections.

Ancestors of the selected dimension value are potential refinements, because selecting one could expand your record set. Those that would change your record set if selected are standard refinements, while those that would not change your record set if selected are implicit refinements.

Dimension values in the subtrees rooted at the siblings of the selected dimension value and its ancestors are also not potential refinements, because they correspond to record sets which are disjoint (or at least uninteresting to the user, based on their selected dimension value.) Note that these dimension values are not available as refinements in single-select dimensions, but are accessible in multiselect-AND dimensions.

Dimension values in the subtrees rooted at the siblings of the selected dimension value and its ancestors are also potential refinements, because selecting one could expand your record set. Those that would change your record set if selected are standard refinements, while those that would not change your record set if selected are implicit refinements.

The process of navigation in a single-select dimension can be conceptualized as walking up and down the dimension value tree. Multiselect-OR dimensions, in constrast, are inverted with respect to refinement generation: dimension values in the subtrees rooted at selections are implicit refinements, while all other dimension values are potential refinements.


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