UML => Sequence Diagram
This diagram basically define the relationships among system, sub systems and actors. So it define the number of action the actor (system also can be a actor) may have.
Sequence Diagram
This diagram is used to explain the sequence the events and flow of an complete operation.
Asp.net, Ado.net, .Net Remoting, .Net
Webservice, SQL, XML, XSLT, WCF, WPF, WWF NHibernate, Ajax, Jquery, DHTML