The diagram below shows a possible layout for a set of track cluster association classes. It is based on Gary Bower's notes, although the detailed implementation is a little different. The basic idea is that a TrackClusterAssociator takes a list of Clusters and a list of Tracks, and produces a TrackClusterAssociationList. From the TrackClusterAssociation list one can get an Enumeration of all the TrackClusterAssociations (getAssociations) or the TrackClusterAssociations for a particlular Track or Cluster (i.e. give me all the associations containing this Track). The TrackClusterAssocationList gives the same functionality as an SLD relational table, although a particular implementation is not specified.