James Rumbaugh (the 3 Amigos of UML) defines that: For example, if the bank changes the business rule to allow the bank balance to be overdrawn by 2000 dollars, the state of the bank account will be redefined with condition that the balance after withdrawal must not be less than $2000 in deficit. The abstraction of the attribute value is a property of the system, rather than a globally applicable rule. This is because the state of the bank account is changed from positive to negative in technical jargon, a transition from the positive state to the negative state is fired. However, if the account balance would become negative after a withdrawal, the behavior of the withdraw function would be quite different. In such situations, the withdrawals do not affect the abstraction of the attribute values, and hence the gross behavior of the object remains unchanged. The behavior of the withdraw function would be: balance:= balance – withdrawAmount provided that the balance after the withdrawal is not less than $0 this is true regardless of how many times you have withdrawn money from the bank. and they are typically used in conjunction with interaction diagrams (usually sequence diagrams).Ĭonsider you have $100,000 in a bank account. State machine diagrams are usually applied to objects but can be applied to any element that has behavior to other entities such as actors, use cases, methods, subsystems systems, etc. An object responds differently to the same event depending on what state it is in. State machine diagrams typically are used to describe state-dependent behavior for an object. Thus, it is often be used for system design and simulation/code generation. Like a sequence diagram, a state machine diagram is a precise and unambiguous specification of behavior. Unlike an activity diagram and a sequence diagram, a state machine diagram focuses attention on how a structure within a system (object, or block instance) changes state in response to event occurrences over time.Ī state machine diagram is well suited to serve as detailed design of a particular classifier (that is, an input into development). A state machine diagram (also known as statechart, state transition diagram or state diagram) is a kind of behavior diagram like an activity diagram and a sequence diagram, it presents a dynamic view of a system.
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