Object nodes

In activity diagrams, an object node is an abstract activity node that helps to define the object flow in an activity. An object node indicates that an instance of a classifier might be available at a particular point in the activity.

The following table describes the types of object nodes that you can use to model object flow in activity diagrams.

Object node type Description Icon
Activity parameter This node specifies the input and output parameters for the activity. A small rectangle, called Activity parameter, is inserted into the left edge of an activity frame.
Central buffer This node consolidates data from several sources and destinations. Central buffer nodes do not connect directly to actions. A rectangle contains the word centralBuffer in double angle brackets.
Data store This node models data flow in which the data is persistent. A rectangle contains the word datastore in double angle brackets.
Input pin This node represents the input parameters on an action. The input pin holds the input values that are received from other actions. A small square is attached to the left side of an action, called OpaqueAction,  and contains an arrowhead that points to the action.
Output pin This node represents the output parameters on an action. The output pin holds the output values that an action produces. Object flow edges deliver the output values to other actions. A small square is attached to the right side of an action, called OpaqueAction2, and contains an arrowhead that points away from the action.
Value pin This node represents the input parameter on an action. The action is enabled when the value pin, which holds a specific value, is evaluated. The result of a "successful" evaluation is the input to the action. A small square is attached to the left side of an action, called OpaqueAction, and contains an arrowhead that points to the action.

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