Be careful when rendering the selected attribute values of multi-or attributes. It is possible to create an interface that might result in dead ends when removing selected attribute values.
Consider this example: an attribute Alpha has been flagged as multi-or, and contains values 1 and 2. Attribute Beta contains value 3.
"Return all records tagged with (1 or 2) and 3"
"Return all records tagged with 2 and 3"
This could result in a dead end if no records are tagged with both value 2 and 3.
Due to this behavior, it is recommended that the user interface be designed so that the user must be forced to remove all values from a multi-or attribute when making changes to the list of selected attribute values.