Module 9 - State Machine Part 1

Question 1

state machines define the behavior of a system . a state machine diagram provides a view of a state machine behavior.

three kinds of behaviors are

Answer 1

state machine shows up on a STM
activity shows up ACT
interaction shows up SD

Question 2

weakness of activity diagram ?

cannot answer which ____ invokes that action

Answer 2

structure

swimlane tells reader which structure performs the action

Question 3

1 not an intuitive diagram

weakness of a sequence diagram ?

#2 harder for people to understand who are not familiar with sysml
#3

Answer 3

3 cannot model an idea to wait before an event is occuring

Question 4

weakness of a state machine diagram

Answer 4

its the most specific behavior .. it defines a set of states and transitions between states as events occurs . BUT not every object falls in line with a state machine diagram

Question 5

an owned behavior is a behavior under a block within your model.
a single block can have multiple behaviors nested

Answer 5

under it

Question 6

classifier behavior

classifier behavior = owned behavior . the attitude control state machine is nested under the block

Answer 6

a classifier behavior is a special role that the behavior plays in the owning block

Question 7

the behavior that you select to be the classifier behavior for a given block is the behavior that will begin executing ___________ when the block is instantiated

Answer 7

automatically

Question 8

two top level categories of elements that a state machine can own
Vertices
Transitions

which are vertices in this diagram ?

Answer 8

orbit insertions

Question 9

knowledge check

two kinds of vertices
1) states
2) pseudo states

and two kinds of transitions
1) external transitions
2)

Answer 9

internal transitions

Question 10

when is an internal tranistion

Question 11

three common kinds of states
1) simple state
2)
3) final state

4) submachine state ( not covered in the course) but its how you represent a nested state machine inside a state machine

Answer 11

composite state

Question 12

two common pseudo states

1) junction pseudo state
2) ______ pseudo state

Answer 12

initial

Question 13

state machines can have multiple _____ represented by dashed lines

Answer 13

regions. Each region must have at least one active state in a region.

Question 14

a state machine may transition from one event to another one when an event occurs.

Question 15

what are the names of the events in this state machine ? when an event occurs a transition may fire resulting in a change in a state.

guard must be true when the event occurs in order for an transition to fire.

Answer 15

startup Event
Shutdown Event

focus on the may if a sensor is in the offline state and a startup event occurs . might happen that powerAvailable == False.

Question 16

“at rest” in a state means the state is looking at the event pool waiting for the state to

Answer 16

occur

Question 17

what happens when an event occurs in a state machine ?

it begins by going to that owning ___________ event pool .

Answer 17

object

The state machine consumes that event pool occurrence . at the moment of consuming an event pool the guard gets evaluated

Question 18

what happens when an outgoing transition fires ?

The run to completion STEP is
#1 Do behavior is terminated
#2 then the run to completion step _____
#3 exit behaviors run and cannot be interrupted
#4 Transition effect behavior cannot be interrupted.
#6 then the next entry behavior is guaranteed to finish

and the state machine is not at rest and is not looking into the event pool.

Answer 18

begins

Question 19

Transition effect behaviors is

when a run to completion step is executing the state machine behavior is not at rest . Its not looking a the owning objects ____ ______

Answer 19

event pool.

Question 20

a state machine is at rest and a trigger event occurs for a transition coming out of a different state

ORBIT INSERTION STATE – what is the run to complete step ( sequence )
1. the STM begins executing and there is a run to completion step in the beginning of the STM.
2. Fire thruster transition executes
3. (entry behavior ) Read Temp executes
the state machine is not at ____while the run to completion step is running

Answer 20

rest

Question 21

ORBIT INSERTION STATE goes into rest behavior and then what behavior executes ?

Answer 21

Do behavior - Execute Spin Stabalization

Question 22

when does a state look at the event pool ?

Answer 22

only when the state is at rest.

Question 23

when does a Do behavior get interrupted ?

Answer 23

when a transition gets fired/begins .

Question 24

the STM has a run to completion step when it executes so the STM is not at rest.
1. entry executes
4. STM is at rest and look at that event pool
2. do
3. exit
sometime later a transfer complete event occurs. the STM is at rest but it detects a new trigger happened and all of the guards get evaluated.

whichever guard is true determine which will

note : another transition is coming out of the orbit insertion state

Answer 24

fire

Question 25

events can trigger a behavior to executing. four common events are 1. 2. change 3. signal 4. time

Answer 25

call

Question 26

Triggerless transition with no Do behavior .. how does it behave ? when does a completion event generate remember a triggerless transition may fire in response to a completion event only if guard = true

Answer 26

the moment the run to completion step is finished. If a state has no Do behavior specified the completion event will be generated the moment the completion step is finished

Question 27

which state is unreachable ? state 3 has no Do behavior and has a behavior4 coming out of it. when does the completion event get generated ? The moment the entry behavior in state 3 gets triggered.

Answer 27

it transitions immediately from state 3 to state 5 state 4 never gets reached .

Question 28

which transition will never fire from the Orbit Insertion state ? how does this get resolved ? -- Add a Do behavior in Orbit insertion - this creates a window of time to be at rest while that Do behavior is running. -- add a guard to Initialize Mans transition -- this creates a window for the transition to Acquisition state to fire

Answer 28

Acquisition transition

Question 29

what is a composite state ? - have nested substates under it.

Answer 29

and how do they work ? - they must have exactly one active state at all times ( same for multiple regions) - could ( optional) have an initial pseudo state - could transition from one state to another when the trigger and guard = true

Question 30

exit and entry - part of a run to completion step when transition fires Do - begins automatically when the rest period of that state ____ also extry , do and exit behaviors are optional slots in states in STM

Answer 30

begins

Question 31

this is legal . transitions can cross over the composite state. If you do this , it does not change the run to completion step. What is different is the starting ____

Answer 31

substate.

Question 32

What are the run to completion steps from acquisition state 1. entry 2. do 3. Activity J transition guard = true 4. Activity K transition guard = true 5. Activity A entry behavior (composite state On station ) 6. Then the state is at rest .. think of a composite state like an onion with layers . tunneling from outer layer into onion layer then after some time , the state is at rest and is looking at the event pool . Now Do behaviors are possible to continue .

Answer 32

Activity C entry behavior ( substate )

Question 33

when a state machine transitions from a composite state. a trigger event occurs and enters the event pool. The composite states are at rest so the state machine consumes it and removes it from the event pool when system error event occurs Activity L transition fires. Doesn't matter which state in the composite states. The Do behaviors in the composite states get ____

Answer 33

aborted

Question 34

when leaving a composite state .. the inner activates execute first and then the outer exit behavior executes then the transition effect executes

Question 35

a check out and check in event occurs . which state will the state machine be in when it comes to rest.

Answer 35

checkedout.unmodifed

Question 36

internal and external transitions