An Identity Manager filter is primarily for controlling which object classes are synchronized and which attributes are synchronized for those object classes. Additionally, other behaviors of those classes and attributes within Identity Manager are controlled through the filter.
An Identity Manager filter consists of a top level <filter> element that contains a set of <filter-class> elements, each of which contains a set of <filter-attr> elements. The filter for a particular driver is stored in the DirXML-DriverFilter attribute on the DirXML-Driver object.
See Filter DTD Elements for a list of all the elements in the Filter DTD.