![]() ![]() Basically, however, the UML 2.5 notation or its equivalent in SysML offers a clear and understandable structure that is easy to create and understand.We will look at Two kinds of diagram that are classed as “interaction” diagrams, Sequence diagrams and Communication diagrams (collaboration diagrams). Although a state diagram should describe the entire behavior of a state machine, it can be very useful to refine details in subordinate diagrams. The behavior diagrams should always be designed in such a way that they can be read easily from top left to bottom right. It is advisable to use state diagrams only for complex objects, because the added value of using state diagrams is rather low for simply structured objects. ![]() Just because state diagrams provide an easy way to display, does not mean that organisations should now only sketch corresponding diagrams. Nevertheless, companies must decide for which objects they want to use state diagrams to describe. Visualisation of the various elements in the form of state diagrams is usually superior to documentation with tables. Due to their logical structure with specified states, transitions, events and conditions, they are ideally suited for modeling workflows using software. They help to describe system behavior and to define requirements. They can be used sensibly in project and product management, in change and risk management, or in requirements engineering. The condition itself cannot trigger a state transition. In contrast, a condition is only checked if an assigned event occurs. In the case of a change event, a condition is permanently checked and a corresponding change of state is triggered if no monitoring condition blocks this. In addition to such signal events, there are call events for the reception of messages, time events for state transitions over time or at defined times and change events. In addition, there is also a behavior that is executed when an event occurs, e.g. A behavior that is executed as long as the state is not changed (do activity).A behavior that is executed when the state machine leaves the state (exit behavior).A behavior that is executed when the state machine enters the state (entry behavior).A state can attach conditions to an event that must be fulfilled before a specific state can be assumed by an event. There are basically three possible behaviors for an event: They consist of a name and assigned arguments. In principle, each state may only have a maximum of one shallow and one deep history state.Įvents trigger transitions. ![]() The shallow history restores the previous state at the same level, while the deep history state activates the last active sub-state over an entire nesting depth. With the shallow and the deep history state, there are two types of history states. History states are used if a transition is to return to the same state that was active before the transition occurred. Each describes a special property that controls the state transitions: The UML 2.5 knows ten different pseudo states. It is not a real state, because there are no value combinations that this state represents. The pseudo state is an element that influences the process of a state machine. In addition to the three types of states, there is a general classification of states: real states in which a system can be permanently located and pseudo states that a system cannot permanently occupy. This is called orthogonal state or super-state. By dividing the state into regions, substates can also be concurrent and active at the same time. If the complex state and exactly one sub-state are active, one speaks of disjoint sub-states. States, which are composed of several sub-states, are also called complex states. The submachine state describes a state that contains sub-states that are represented in a subordinate state diagram. Open and closed would be corresponding sub-states. For example, a door could know two states unlocked and locked and be open or closed in the unlocked state. Sub-states are possible with the composite state.
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