While a control flow connects actions and activities and expresses a dependency between predecessor and successor nodes, an object flow additionally transmits data between the accounts. control flows or control flow edges and.A collection output combines individual elements generated by the execution of the region into a collection for use outside the region. A collection input of an expansion region contains a collection that is broken down into its individual elements within the region and whose content is executed once per element. expansion nodes used to specify a collection input or output for an expansion region.Data is persistently stored in data store nodes. central buffer nodes, which act as buffers between incoming and outgoing edges, consolidating data from different sources, but without being directly related to actions.A “special” input parameter is the value pin, which activates an action if the evaluation of a value specification provides a defined value. A distinction is made between input parameters or input pins and output parameters or output pins. activity parameter nodes for passing parameters when calling actions.Object nodes form the structure for transporting data and values within an activity during a process their specification defines the flow of the objects. The end node is represented by a black circle with a white border. The end node or activity final for the immediate termination of all flows in an activity, even if activities have several end nodes. The flow end is represented by a crossed circle. the flow final, which ends the flow in an activity, but without influencing other flows in the activity.the merge node as a point in an activity where several edges are merged into a common edge without synchronisation.The join is represented as a bar with several incoming and one outgoing edge. the join node as a point in an activity where several flows are synchronised into a common flow accordingly, we speak of synchronisation.The fork is represented as a bar with one incoming and several outgoing edges. the fork node as a point in an activity that divides a flow into several parallel or concurrent flows. Decision nodes are represented as diamonds. Implicit decisions exist when alternative sequences are represented without the use of a decision node since this can lead to erroneous interpretations, implicit decisions should also be avoided. the decision nodes, which offer explicit decision options – usually linked to conditions – for alternative processes.The start node is represented by a black circle. If there are several initial nodes, activities are started in parallel if the initial node is missing, all activities with no incoming edges start in parallel. the initial node – also called the start node – as the initial starting point for a flow.2 Edges are the connecting lines between nodes, nodes are the points where “something” happens.Īctivity nodes represent both actions that receive inputs and process them into outputs for other nodes, or call up other activities, and groups of actions.Ĭontrol nodes direct the flow of an activity, including the specification of alternative flows through branches or unions. In the UML 2.5 specification of the Object Management Group (OMG), the terms nodes and edges appear 1,986 and 786 times respectively. link-related actions for navigation or for creating or deleting links between objects.Īctions are represented with rounded rectangles within an activity.variable-related actions such as setting or deleting individual values of variables, or.object-related actions for creating and deleting objects,.communication-related actions for signals and events,. The UML categorises 44 types of actions, e.g. The sum of the actions determines the behavior of an activity. It can be executed repeatedly and can call up other actions or activities. It is represented as a rounded rectangle.Īn action is an atomic component of an activity. To understand activity diagrams, it is important to distinguish between different terms: Activities and ActionsĪn activity describes the sequence of actions and can have input and output parameters as preconditions or postconditions that must apply when the activity begins or ends. Essential Elements in the Activity Diagram
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