The Structural Model View Class diagrams depict the static structure of a system. Object diagrams depict the static structure of a system at a particular time. The Behavioral Model View Sequence diagrams depict the specification of behavior. Collaboration diagrams depict the realization of behavior. State diagrams depict the status conditions and responses of participants involved in behavior.
Activity diagrams depict the activities of participants involved in behavior.
The Implementation Model View Component diagrams depict the organization of solution components. The Environment Model View Deployment diagrams depict the configuration of environment elements and the mapping of solution components onto them. Other diagrams may be defined and used as necessary. Something is necessary if it is required, and sufficient if it, by itself, is enough to satisfy a given purpose. Sinan Si Alhir .