[Zope-dev] Keyword Indexes in ZCatalogs

Hello, Could someone explain how to use Keyword Indexes in ZCatalogs? In a ZCatalog, we now have 3 index types: Text Index, Field Indexes and Keyword Indexes. Here is the information I have found so far about the Keyword type: "Keyword Indexes index a sequence of objects that act as 'keywords' for an object. A Keyword Index will return any objects that have one or more keywords specified in a search query." (source: Indexes tab of a Zcatalog) "Keyword Index: Subclasses all of the field index behavior, except that property values are treated as a sequence of keywords." (source: posting on a Zope list) Could someone provide an implementation example? Thanks. Alexandre