Why State Chart Diagram Diagrams ( State Machine Diagram in UML 2 )

So why do we need State Chart Diagrams. People often make good use of Sequence and class diagram as they are largely most popular diagrams that developer makes use of. State Chart Diagrams are very powerful diagrams when it comes to depicting LOGIC. So ask yourself this question - how can I depict business logic in UML. Well sequence diagram is certainly not the answer. Sequence diagrams are for representing control flow logic between objects and not business logic. State chart diagram should do a good job for representing business logic. Lets take an example. An account can exist in many states - 'under process of opening', normal, suspended , closed, 'not used for last 6 months', etc. What business, operation can be performed on a account depends on what state it is in. Consider using state chart diagrams for representing your business logic around account manipulation. Activity Diagram is also a good way of representing business logic. In most cases, a combination of 'Activity Diagram' and 'State Chart' diagram is good for depicting Business Logic.