![]() When attached to state it means that the state responds to an event with an action that does not cause a transition. They are used to label transitions but can also be used within states. Identifying the Elements of a Statechart DiagramĪction blocks name the event and say what action is to be take. When the outside temperature gets above the LOWER bound the heating is turned off AND the fan is switched off.įirst go at the State Machine diagram Showing main elements. When the outside temperature gets below a LOWER bound ( and heater is installed) - a fan is switched on AND then the heating is turned on. If the Temperature gets too cold – we will turn ON the Heater and the Fan until it reaches a required temperature – and then they will be switched off When the outside temperature gets below the UPPER bound the air-conditioning is turned off AND the fan is switched off. When the outside temperature gets above an UPPER bound ( and air conditioning is installed) - a fan is switched on AND then the air-conditioning is turned on. If the Temperature gets too hot – we will turn ON the Air-conditioning and the Fan until it reaches a required temperature – and then they will be switched off If the Temperature gets too cold – we will turn ON the Heater and the Fan until it reaches a required temperature – and then they will be switched off. If the Temperature gets too hot – we will turn ON the Air-conditioning and the Fan until it reaches a required temperature – and then they will be switched off. ![]() Imagine an Object that controls a Heating, Ventilation and Air-Conditioning system (HVAC). Will now look at an Example of a detailed state machine diagram. The state is derivable from the attributes and links and is of sufficient interest in its own right as to be worth modelling separately. The state of an object describes the behaviour of the object relative to external stimuli.Īn object’s state can be thought of as an abstraction of a particular set of attribute values and links to other objects. The state of an object is a specific collection of attribute values for the object. There are two ways to think about object state: They also shows all that possible ways in which objects can respond to events form either other objects, or from outside the system. They shows the allowable states for objects of a specific class and the permitted transitions between states. The UML style is based on David Harel’s statechart.Ī State diagram, also know as Statechart diagram and a Satechart diagram, shows the behaviour of one object and how it changes its state in response to events, together with its responses and actions. There are many forms of state diagrams, each with slightly different semantics. In most OO techniques, state diagrams are drawn for a single class to show the lifetime behaviour of a single object. They describe all the possible states that a particular object can get into and how the object’s state changes as a result of events that reach the object. State diagrams describe the behaviour of a system. States are therefore useful logical views of an entity. ![]() When making a call there is a lot of activity in the phone. when you hang up a phone there is no activity in the phone. While an item is in a particular state work may or may not be going on, i.e. These are states of the phone and we can use a state diagram to link the states together and determine the legal flows through the system. It may be ‘hung up’, ‘dialling’, ‘engaged in a call’, or ‘disconnected’. For example, a telephone has different states. Activity diagrams describes the flow between areas of work, whereas state diagrams describe the changes between the states of instances. State diagrams are closely related to activity diagrams. We will look at Communication (collaboration) diagrams in the next lecture.Īctivity Diagrams Describe the flow of work Parallel processing Sequence Diagrams Describe the sequence of messages passed between objects State Machine Describe the behaviour of single objects Communication diagrams show same interaction in the context of the classes that participate in the interaction and the structural relationships of the classes to one another. Sequence diagrams show interactions and emphasise the order of the messages over time. We will look at Two kinds of diagram that are classed as “interaction” diagrams, Sequence diagrams and Communication diagrams (collaboration diagrams).
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