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An activity parameter node is an object node for inputs and outputs to activities.
•
ObjectNode (from BasicActivities , CompleteActivities ) on page 408
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Activity parameter nodes are object nodes at the beginning and end of flows that provide a means to accept inputs to an activity
and provide outputs from the activity, through the activity parameters.
Activity parameters inherit support for streaming and exceptions from Parameter.
No additional attributes
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• parameter : Parameter [1..1] The parameter the object node will be accepting or providing values for.
[1] Activity parameter nodes must have parameters from the containing activity.
[2] The type of an activity parameter node is the same as the type of its parameter.
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[3] An activity parameter node may have either all incoming edges or all outgoing edges, but it must not have both incoming
and outgoing edges.
[4] Activity parameter object nodes with no incoming edges and one or more outgoing edges must have a parameter with in or
inout direction.
[5] Activity parameter object nodes with no outgoing edges and one or more incoming edges must have a parameter with out,
inout, or return direction.
See
Action (from CompleteActivities , FundamentalActivities , StructuredActivities) on page 323.
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As a kind of behavior, an activity may have owned parameters. Within the activity, in and inout parameters may be associated
with activity parameter nodes that have no incoming edges—they provide a source within the activity for the overall input
values of the activity. Similarly, inout, out, and return parameters may be associated with activity nodes that have no outgoing
edges—they provide a sink within the activity for the overall output values of the activity.
Per the general semantics of a behavior, when the activity is invoked, its in and inout parameters may be given actual values.
These input values are placed as tokens on those activity parameter nodes within the activity that are associated with the
corresponding in and inout parameters, the ones which do not have incoming edges. The overall activity input values are then
available within the activity via the outgoing edges of the activity parameter nodes.
During the course of execution of the activity, tokens may flow into those activity parameter nodes within the activity that
have incoming edges. When the execution of the activity completes, the output values held by these activity parameter nodes
are given to the corresponding inout, out and return parameters of the activity.
If the parameter associated with an activity parameter node is marked as streaming, then the above semantics are extended
to allow for inputs to arrive and outputs to be posted during the execution of the activity (see the semantics for Parameter).
In this case, for an activity parameter node with no incoming edges, an input value is placed on the activity parameter node
whenever an input arrives on the corresponding streaming in or inout parameter. For an activity parameter node with no outgoing
edges, an output value is posted on the corresponding inout, out or return parameter whenever a token arrives at the activity
parameter node.
The label for parameter nodes can be a full specification of the corresponding parameter.
Also see notation at Activity.
Figure 12.52 - Activity notation
The figure below shows annotations for streaming and exception activity parameters, which are the same as for pins. See Parameter
for semantics of stream and exception parameters.
Figure 12.53 - Activity notation
If the round-cornered border of Figure 12.53 is replaced with the frame notation that is described in Annex A, then
activity parameter nodes overlap the frame instead. If the round-cornered border or frame is omitted completely, then the
activity parameter nodes can be placed anywhere, but it is clearer if they are placed in the same locations they would be
in if the frame or border was shown.
The presentation option at the top of the activity diagram below may be used as notation for a model corresponding to the
notation at the bottom of the diagram.
See presentation option for Pin when parameter is streaming. This can be used for activity parameters also.
In the example below, production materials are fed into printed circuit board. At the end of the activity, computers are quality
checked.
In the example below, production materials are streaming in to feed the ongoing printed circuit board fabrication. At the
end of the activity, computers are quality checked. Computers that do not pass the test are exceptions. See Parameter for
semantics of streaming and exception parameters.
{stream}
Activity parameter nodes are introduced to model parameters of activities in a way that integrates easily with the rest of
the flow model.
ActivityParameterNode is new in UML 2.0.