I am creating use cases for a project.  A generic user is extended by user categories which then is extended by an administrator (that can do all tasks possible).  Is the following acceptable to portray? Is there a better way to portray such info?sample use case http://i43.tinypic.com/adm0b4.jpg
Use Case Structure
requirements;use case
Yes.  This is acceptable.  Making all actors a subclass of User is needless.  That goes without saying.The original Objectory method (on which UML is based) explicitly makes the case that Actor is a kind of classifier, and has subclasses and superclasses.Don't go crazy however.  The inheritance among users should be kept quite simple.