Object flow (UML)

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An object flow (engl. Object Flow ) is a model element in the Unified Modeling Language (UML), a language for the modeling of the structures and the behavior of software - and other systems.

An object flow is a special activity edge in an activity . It connects object nodes and control nodes . He can never connect an action directly to an object node or to a control node, but only indirectly via pins that are assigned to the action.

A modeler can control the "conductivity" of an object flow in two ways. First, it can provide the object flow with a so-called guard , a Boolean expression that is always evaluated when the producing action offers the object flow a token. The token can only flow if this expression evaluates to true. Secondly, the object can flow with a weight (engl. Weight are) provided. Weight is a positive number. It specifies the minimum number of tokens that must be present in the source object node before all available tokens flow together across the object flow. The weight is a modeling parameter that defines a kind of “package size” for object flows.

An object flow is more than a transport channel between two object nodes, because two separate instruments are assigned to it in order to influence the flow of tokens through an activity:

  1. Selection behavior (. Engl selection behavior ): An object flow can a selection behavior select the objects in the source object node using that should flow through him. The source object node offers so all objects waiting on , while the specification of the selection behavior determines which objects actually flow . A selection behavior can be formulated in one of the admissible forms for a behavior specification, for example as an activity , interaction or as a state machine .
  2. Transformation behavior (. Engl transformation behavior ): An optional transformation behavior can specify an object flow as an object that passes through the object flow is changed.

notation

Example of an object flow with explicit modeling of the end pins.
Example of an object flow with hidden end pins.
Example of an object flow whose end pins are represented as an object node.

Difference to UML 1.x

The object flow model element was newly introduced in UML2.

See also