Activity Diagrams

Question 1

What is the diagram kind of the activity diagram, and what kinds of model elements does the frame correspond to?

Answer 1

(232)
diagram kind: act
model elements: activity, control operator

Question 2

How are an action and its pins typically represented on an activity diagram?

Answer 2

input and output pins are shown as small rectangles and accept tokens that may represent units of information, mater, or energy. Pins are connected using object flows (solid lines) and control flows (dashed lines)

Question 3

What does an action with control and object flows require before it starts executing?

Answer 3

As long as the owning activity is executing, an action will begin when tokens are available on all its required inputs including its control inputs.

• the number of tokens available at each required input pin is equal to or greater than its lower multiplicity bound.
• a token is available at each of the actions incoming control flows.

Question 4

How are the parameters of activities shown on activity diagrams?

Answer 4

(235)

activity parameters: activity parameter nodes on the frame of the activity diagram.

Question 5

What is the difference between a streaming and non streaming parameter?

Answer 5

(236)
non streaming: nonstreaming input params only accept tokens prior to the start of the activity execution output params and only provides tokens once after the activity is done executing
streaming: continues to accept input tokens or produce output tokens throughout execution

Question 6

How are parameters with a lower -multiplicity bound of 0 on an act diagram?

Answer 6

param name : Param Type [0..*]

Question 7

How are the set of pins for a call behavior action determined?

Answer 7

(237)

Question 8

How are the set of pins for a call behavior action determined?

Answer 8

(237)
call behavior action: invokes a behavior when it is executed. The invoked behavior is assumed to be an activity (but could be something else).
It has a pin for each parameter of the called behavior, and the characteristics of those pins must match the multiplicity and type of their corresponding parameters on the invoked behavior.

Question 9

What is an object flow used for and how is it represented>

Answer 9

used to route input/output tokens that represent information and/or physical items between object nodes.
represented by: arrow connecting the source of the flow to the destination of the flow, with its head at the destination.

Question 10

How does the behavior of a join node differ from a merge node?

Answer 10

• join node: has an output flow and one or more input flows with a default behavior to product output tokens only when an input token is available at each input flow.
• merge node: has one out put flow and more or more input flows and routes each input toked recieved on any of its input flow to the output flow. it does not require tokens on all input flows.

Question 11

How does the behavior of a fork node differ from a decision node?

Answer 11

• fork node: has one input flow with 1 or more output flows. it replicates every input token it receives onto each of its output flows which may be handled independently and concurrently. It does not imply that the actual tokens are replicated (which may not be physically possible).
• decision node: has 1 input and 1 or more output flows - an input token can only traverse one output flow typically established by placing mutually exclusive guards on all outgoing flows and offering the token to the flow whose guard is satisfied.

Question 12

What are parameter sets used for how are they represented, both in the definition and the invocation of an activity?

Answer 12

• parameter sets: a set of only in or out parameters as members.
• invocation: When an activity is invoked that has input parameter sets, the parameter nodes corresponding to at most one input parameter set can contain tokens. When an activity that has output parameter sets completes, the parameter nodes corresponding to at most one output parameter set can contain tokens.