28 déc. L’événement à l’origine de la transition, les activités invoquées pendant la La norme UML de concept de machine d’état est suffisante pour. Utiliser des diagrammes UML pour modéliser un objet d’étude. Interpréter Les événements déclenchent les transitions d’un état vers un autre. Evénement.
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A state diagram is a type of diagram used in computer science and related fields to describe the behavior of systems.
State diagrams require that the system described is composed of a finite number of states ; sometimes, this is indeed the case, while at other times this is a reasonable abstraction. Many forms of state diagrams exist, which differ slightly and have different semantics. State diagrams are used to give an abstract description of the behavior of a system. This behavior is analyzed and represented as a series of events that can occur in one or more possible states.
Hereby “each diagram usually represents objects of a single class and track the different states of its objects through the system”. State diagrams can be used to graphically represent finite state machines. This was introduced by C. Weaver in their book “The Mathematical Theory of Communication”.
Another possible representation is the State transition table.
There are also variants that combine these two notations. For example, if a state has a number of outputs e.
This designator will be written inside the state’s circle. S 1 and S 2 are states and S 1 is an accepting state or a final state.
Each edge is labeled with the input. Harel statecharts  are gaining widespread usage since a variant has become part of the Unified Modeling Language UML. Classic state diagrams require the creation of distinct nodes for every valid combination of parameters that define the state.
This can lead trwnsition a very large number of nodes and transitions between nodes for all but the simplest of systems state and transition explosion. This complexity reduces the readability of the state diagram. With Harel statecharts it is possible to model multiple cross-functional state diagrams within the statechart.
Each of these cross-functional state machines can transition internally without affecting the other state machines in the statechart.
The current state of each cross-functional state machine in the statechart defines the state of the system. The Harel statechart is u,l to a state diagram but it improves the readability of the resulting diagram.
There are other sets of semantics available to represent state diagrams. For example, there are tools for modeling and designing logic for embedded controllers.
Newcomers to the state machine formalism often confuse state diagrams with flowcharts. The figure below shows a comparison of a state diagram with a flowchart. A state machine panel a performs actions in response to explicit events. In contrast, the flowchart panel transitionn does not need explicit events but rather transitions from node to node in diaggramme graph automatically upon completion of activities.
Nodes of flowcharts are edges in the induced graph of states. The reason is that each node in a flowchart represents a program command. Diagrammd program command is an action to be executed. So it is not a state, but when applied to the program’s state, it results in a transition to another state. In more detail, the source code listing represents a program graph. Executing the program graph parsing and interpreting results in a state graph. Daigramme each program graph induces a state graph.
Conversion of the program graph to its associated state graph is called “unfolding” of the program graph. The program graph is a sequence of commands. If no variables exist, then the state consists only of the program counter, which keeps track of where in the program we are during execution what is the next command to be applied.
In this case before executing a command the program counter is at some position state before the command is executed. Executing the command moves the program counter to the next command.
Since the program counter is the whole state, it follows that executing the command changed the state. So the command itself corresponds to a transition between the two states.
Now consider the full case, when variables exist and are affected by the program commands being executed. Then between different program counter locations, not only does the program counter change, but variables might also change values, due to the commands executed. Consequently, even if we revisit some diatramme command e. In the previous case, the program would be in the same state, because the whole state is just the program counter, so if the program counter points to the diagramem position next command it suffices to specify that we are in the same state.
However, if the state includes variables, then if those change value, we can be at the same program location with different variable values, meaning in a different ttransition in the program’s state space. The term “unfolding” originates from this multiplication of locations when producing the state graph from the program graph.
Tarnsition representative example is a do loop incrementing some counter until it overflows and diabramme 0 again. Although the do loop executes the same increment command iteratively, so the program graph executes a cycle, in its state space is not a cycle, but a line.
This results from the state being the program location here cycling combined with the counter value, which is strictly increasing until the overflowso different states are visited in sequence, until the overflow.
After the overflow the counter becomes 0 again, so the initial state is revisited in the state space, closing a cycle in etta state space assuming the counter was initialized to 0. The figure above attempts to show that reversal of roles by aligning the arcs of the state diagrams with the processing stages of the flowchart.
You can compare a flowchart to an assembly line in manufacturing because the flowchart describes the progression of some task from beginning to end e.
A state machine generally has no notion of such a progression. A state in a state machine is an efficient way of specifying a particular behavior, rather than a stage of processing. An interesting extension is to allow arcs to flow from any diagrame of states to any number transjtion states. This only makes sense if the system is allowed to be in multiple states at once, which implies that an diargamme state only describes a condition or other partial aspect of the overall, global state.
The resulting formalism is known trqnsition a Petri net. Another extension allows the integration of flowcharts within Harel statecharts. This extension supports the development of software that is both event driven and workflow driven. From Wikipedia, the free encyclopedia. A visual formalism for complex systems. Science of Computer Programming8 3: A Visual Formalism for Complex Systems.
Science of Computer Programming— International Diagdamme on Embedded Software pp. Event-Driven Programming for Embedded Systems. Object-oriented programming Object-oriented analysis and design Object-oriented modeling. Association Composition Dependency Generalization or Inheritance. Activity State Machine Use case. Communications Sequence Interaction overview Timing. Retrieved from ” https: Webarchive template wayback links All pages needing factual verification Wikipedia articles needing factual verification from March Commons category link is on Wikidata Use dmy dates from May Views Read Edit View history.