How can a collaboration diagram properly (per UML) show a related (or "sub") use case? Can a use-case oval appear on a collaboration diagram? For example, if 2 use-cases include/share another use case, how can the collaboration diagrams for the parent use cases direct the flow to another collaboration diagram (for the sub use case)? Also -- I noted that Cade's collaboration diagrams do not show the interaction between his DAOs and the actual data source (presumably a relational data source accessed by JDBC). Should it? Should a collaboration diagram simply "stop" at the DAO or entity-bean point? Or should it somehow show the data source and the message going to it?