SCXML State Chart XML

Transcription

1 SCXML State Chart XML Previously, in this course...

2 Previously, in this course... Running Example all actions omitted wasn t it supposed to help?

3 Previously, in this course... Running Example all actions omitted Substates may be nested to any level. A nested state machine may have at most one initial state and one final state. Substates are used to simplify to complex wasn t it supposed help?flat state machines by showing that some states are only possible within a particular (the State enclosing Finite context State Machine, Charts state). A composite state factorizes the possible exits from all (most of) the states

4 Previously, in this course... Running Example all actions omitted A simple state is one which has no substructure. A state which has substates (nested states) is called a composite state (or compound state). Substates may be nested to any level. A nested state machine may have at most one initial state and one final state. Substates are used to simplify complex flat state machines by showing that some states are only possible within a particular context (the enclosing state). A composite state factorizes the possible exits from all (most of) the states

5 Previously in this course... Stopwatch A simple state is one which has no substructure. A state which has substates (nested states) is called a composite state (or compound state). Substates may be nested to any level. A nested state machine may have at most one initial state and one final state. Substates are used to simplify complex flat state machines by showing that some states are only possible within a particular context (the enclosing state). A composite state factorizes the possible exits from all (most of) the states Taken and modified from

6 Previously, in this course... History state Deep or shallow... <history> <history> allows allows for for pause pause and and resume resume semantics semantics in in compound compound states states.. Before Before the the state state machine machine exits exits aa compound compound state, state, itit records records the the state's state's active active descendants. descendants. IfIf the the 'type' 'type' attribute attribute of of the the <history> <history> state state is is set set to to "deep", "deep", the the state state machine machine saves saves the the state's state's full full active active descendant descendant configuration, configuration, down down to to the the atomic atomic descendant(s). descendant(s). IfIf 'type' 'type' is is set set to to "shallow", "shallow", the the state state machine machine remembers remembers only only which which immediate immediate child child was was active. active. After After that, that, ifif aa transition transition takes takes aa <history> <history> child child of of the the state state as as its its target, target, the the state state machine machine rereenters enters not not only only the the parent parent compound compound state state but but also also the the state(s) state(s) in in the the saved saved configuration. configuration. Thus Thus aa transition transition with with aa deep deep history history state state as as its its target target returns returns to to exactly exactly where where the the state state was was when when itit was was last last exited, exited, while while aa transition transition with with aa shallow shallow history history state state as as aa target target re-enters re-enters the the previously previously active active child child state, state, but but will will enter enter the the child's child's default default initial initial state state (if (if the the child child is is itself itself compound.). compound.).

7 TD stopwatch

8 TD stopwatch Column 1 Column 2 Column Row 1 Row 2 Row 3 Row 4

9 TD stopwatch Est-ce correct?

10 TD stopwatch

11 TD stopwatch Composite states are also named OR-states since, if the machine is in the StopWatchMode, then it can be in the ready substate, OR the stopped substate OR the TimePassing substate I believe this can be missleading...

12 TD stopwatch and hierarchy! revisited

13 SCXML State Chart XML Parallel regions, communications and a little bit more

14 State Charts David Harel Statecharts: A visual formalism for complex systems Science of computer programming 8 (3),

15 Parallel states Also named Orthogonal regions in UML or AND-States (Since after initialization, the machine is in substate State_2_1 AND State_3_1.) Everything is working as if State_2 and State_3 were independent. When the machine is in a parallel state, all event received are broadcasted to all the parallel states. They can consume them or not like any normal state machine

16 Parallel states external queue external queue Also named Orthogonal regions in UML or AND-States (Since after initialization, the machine is in substate State_2_1 AND State_3_1.) Everything is working as if State_2 and State_3 were independent. When the machine is in a parallel state, all event received are broadcasted to all the parallel states. They can consume them or not like any normal state machine

17 Parallel states The Cartesian product of the states allows for sequential equivalence of the input language but warning about the actions, i.e., the behavior of the system!! By using parallel states, the complexity in number of state is the sum of the number of states in each parallel states while otherwise it is the product of them (if we add another parallel state with 3 states, the sequential result have 12 states)

18 Parallel states Other representations and naming: UML From Charles André s slides

19 Parallel states Other representations and naming: UML From Charles André s slides UML syntax is more complex than scxml since no reuse is done (e.g., about the datamodel)

20 Parallel states Yet another representation and naming concurrent substates specify two or more state machines that execute in parallel in the context of the enclosing object Execution of these concurrent substates continues in parallel. These substates waits for each other to finish to joins back into one flow A nested concurrent state machine does not have an initial, final, or history state Mix with the vocabulary from activity diagrams

21 Parallel states Yet another representation and naming concurrent substates specify two or more state machines that execute in parallel in the context of the enclosing object Execution of these concurrent substates continues in parallel. These substates waits for each other to finish to joins back into one flow A nested concurrent state machine does not have an initial, final, or history state

22 Parallel states Parallel Parallel States: States: The The child child states states execute execute in in parallel parallel in in the the sense sense that that any any event event that that is is processed processed is is processed processed in in each each child child state state independently, independently, and and each each child child state state may may take take aa different different transition transition in in response response to to the the event. event. (Similarly, (Similarly, one one child child state state may may take take aa transition transition in in response response to to an an event, event, while while another another child child ignores ignores it.) it.) When When all all of of the the children children reach reach final final states, states, the the <parallel> <parallel> element element itself itself is is considered considered to to be be in in aa final final state, state, and and aa completion completion event event done.state.id done.state.id is is generated, generated, where where id id is is the the id id of of the the <parallel> <parallel> element. element. Transitions Transitions within within the the individual individual child child elements elements operate operate normally. normally. However However whenever whenever aa transition transition is is taken taken with with aa target target outside outside the the <parallel> <parallel> element, element, the the <parallel> <parallel> element element and and all all of of its its child child elements elements are are exited exited and and the the corresponding corresponding <onexit> <onexit> handlers handlers are are executed. executed. The The handlers handlers for for the the child child elements elements execute execute first, first, in in document document order, order, followed followed by by those those of of the the parent parent <parallel> <parallel> element, element, followed followed by by an an action action expression expression in in the the <transition> <transition> element, element, and and then then the the <onentry> <onentry> handlers handlers in in the the "target" "target" state. state. Note Note that that the the semantics semantics of of the the <parallel> <parallel> element element does does not not call call for for multiple multiple threads threads or or truly truly concurrent concurrent processing. processing. The The children children of of <parallel> <parallel> execute execute in in parallel parallel in in the the sense sense that that they they are are all all simultaneously simultaneously active active and and each each one one independently independently selects selects transitions transitions for for any any event event that that is is received. received. However, However, the the parallel parallel children children process process the the event event in in aa defined, defined, serial serial order, order, so so no no conflicts conflicts or or race race conditions conditions can can occur. occur. See See D D Algorithm Algorithm for for SCXML SCXML Interpretation Interpretation for for aa detailed detailed description description of of the the semantics semantics of of <parallel> <parallel> and and the the rest rest of of SCXML. SCXML.

23 Parallel states Parallel Parallel States: States: The The child child states states execute execute in in parallel parallel in in the the sense sense that that any any event event that that is is processed processed is is processed processed in in each child state independently, and each child state may take a different transition in response to each child state independently, and each child state may take a different transition in response to the the event. event. (Similarly, (Similarly, one one child child state state may may take take aa transition transition in in response response to to an an event, event, while while another another child child ignores ignores it.) it.) When When all all of of the the children children reach reach final final states, states, the the <parallel> <parallel> element element itself itself is is UML: considered considered to to be be in in aa final final state, state, and and aa completion completion event event done.state.id done.state.id is is generated, generated, where where id id is is the id <parallel> Even regions imply independence of execution (allowing more or less thethough id of of the theorthogonal <parallel> element. element. Transitions the child elements However whenever aa transition Transitions within within the individual individual child does elements operate normally. normally. Howeverthread whenever transition concurrency), the UML specification not operate require that a separate of execution is aa target outside <parallel> element, and of child is taken taken with with target outside the the <parallel> element, the <parallel> element and all all fact, of its itsmost child be assigned to each orthogonal region (although thisthe can<parallel> be doneelement if desired). In elements elements are are exited exited and and the the corresponding corresponding <onexit> <onexit> handlers handlers are are *executed. executed. The The handlers handlers for for the the commonly, orthogonal regions execute within the same thread. The UML specification child child elements elements execute execute first, first, in in document document order, order, followed followed by by those those of of the the parent parent <parallel> <parallel> requires only that the designer does not rely on any particular order for event instances to element, followed by an action expression in the <transition> element, and then the <onentry> element, followed by an action expression in the <transition> element, and then the <onentry> handlers state. be dispatched handlers in in the the to "target" "target" the relevant state. orthogonal regions. Note Note that that the the semantics semantics of of the the <parallel> <parallel> element element does does not not call call for for multiple multiple threads threads or or truly truly concurrent concurrent processing. processing. The The children children of of <parallel> <parallel> execute execute in in parallel parallel in in the the sense sense that that they they are are all all simultaneously simultaneously active active and and each each one one independently independently selects selects transitions transitions for for any any event event that that is is received. received. However, However, the the parallel parallel children children process process the the event event in in aa defined, defined, serial serial order, order, so so no no conflicts conflicts or or race race conditions conditions can can occur. occur. See See D D Algorithm Algorithm for for SCXML SCXML Interpretation Interpretation for for aa detailed detailed description description of of the the semantics semantics of of <parallel> <parallel> and and the the rest rest of of SCXML. SCXML. * Douglass, Bruce Powel (1999). Doing Hard Time: Developing Real-Time Systems with UML, Objects, Frameworks, and Patterns. Addison Wesley. p ISBN

24 SCXML State Chart XML Parallel regions, communications and a little bit more

25 State Charts David Harel Statecharts: A visual formalism for complex systems Science of computer programming 8 (3),

26 Communication: intuition Usually, parallel states are not truly independent. The different state machines can communicate through different mechanism (e.g., shared variable or timings) to synchronize their behaviors. The most common way to coordinate behaviors from parallel states is by sending events to each others. /ping /pong onentry: send dopong after 1s

27 Communication: intuition Usually, parallel states are not truly independent. The different state machines can communicate through different mechanism (e.g., shared variable or timings) to synchronize their behaviors. The most common way to coordinate behaviors from parallel states is by sending events to each others. /ping /pong onentry: send dopong after 1s

28 Communication: intuition Usually, parallel states are not truly independent. The different state machines can communicate through different mechanism (e.g., shared variable or timings) to synchronize their behaviors. The most common way to coordinate behaviors from parallel states is by sending events to each others. /ping /pong onentry: send dopong after 1s

29 Communication: intuition The coordination between the parallel states can reduce the resulting behavior /ping /pong onentry: send dopong after 1s

30 Communication: intuition The coordination between the parallel states can reduce the resulting behavior /ping /pong onentry: send dopong after 1s Demo...

31 Communication: intuition The coordination between the parallel states can reduce the resulting behavior /ping /pong onentry: send dopong after 1s onentry: send dopong after 1s

32 Communication: intuition The coordination between the parallel states can reduce the resulting behavior If ping or pong is not sent from the outside! /ping /pong onentry: send dopong after 1s onentry: send dopong after 1s

33 SCXML State Chart XML Parallel regions, communications and a little bit more

34 No target transition IfIf the the 'target' 'target' on on aa <transition> <transition> is is omitted, omitted, then then the the value value of of 'type' 'type' does does not not have have any any effect effect and and taking taking the the transition transition does does not not change change the the state state configuration configuration but but does does invoke invoke the the executable executable content content that that is is included included in in the the transition. transition. Note Note that that this this is is different different from from aa <transition> <transition> whose whose 'target' 'target' is is its its source source state. state. In In the the latter latter case, case, the the state state is is exited exited and and reentered, reentered, triggering triggering execution execution of of its its <onentry> <onentry> and and <onexit> <onexit> executable executable content content

35 Non Determinism? N.B. N.B. IfIf two two transitions transitions conflict, conflict, then then taking taking them them both both may may lead lead to to an an illegal illegal configuration. configuration. Hence, Hence, only only one one of of the the transitions transitions may may safely safely be be taken. taken. In In order order to to resolve resolve conflicts conflicts between between transitions, transitions, we we assign assign priorities priorities to to transitions transitions as as follows: follows: let let transitions transitions T1 T1 and and T2 T2 conflict, conflict, where where T1 T1 is is optimally optimally enabled enabled in in atomic atomic state state S1, S1, and and T2 T2 is is optimally optimally enabled enabled in in atomic atomic state state S2, S2, where where S1 S1 and and S2 S2 are are both both active. active. We We say say that that T1 T1 has has aa higher higher priority priority than than T2 T2 ifif a) a) T1's T1's source source state state is is aa descendant descendant of of T2's T2's source source state, state, or or b) b) S1 S1 precedes precedes S2 S2 in in document document order. order.

36 Raise vs send / send action1 / send action2 / raise in2 / send action2 The The <raise> <raise> element element raises raises an an event event in in the the current current SCXML SCXML session. session. Note Note that that the the event event will will not not be be processed processed until until the the current current block block of of executable executable content content has has completed completed and and all all events events that that are are already already in in the the internal internal event event queue queue have have been been processed. processed. For For example, example, suppose suppose the the <raise> <raise> element element occurs occurs first first in in the the <onentry> <onentry> handler handler of of state state S S followed followed by by executable executable content content elements elements ec1 ec1 and and ec2. ec2. IfIf event event e1 e1 is is already already in in the the internal internal event event queue queue when when S S is is entered, entered, the the event event generated generated by by <raise> <raise> will will not not be be processed processed until until ec1 ec1 and and ec2 ec2 have have finished finished execution execution and and e1 e1 has has been been processed. processed. <send> <send> is is used used to to send send events events and and data data to to external external systems, systems, including including external external SCXML SCXML Interpreters, Interpreters, or or to to raise raise events events in in the the current current SCXML SCXML session. session.

37 Datamodel It is possible to add data and data manipulation directly inside the state machine. SCXML supports the ecmascript data model (some sort of C++ in Qt Creator and a specific action langage in Yakindu) Usually*, only data directly associated with the control is used in the state machine To avoid mixing the application logic between the code and the state chart To ease the V&V activities * it strongly depends on what the state chart is used for but it seems to be a good practice, even for understanding

38 Datamodel When ecmascript data model is used, the log expr must not be null and it must conform the ecmascript syntax otherwise no log is printed

39 Datamodel Variables are declared and initialized in a specific section id: The name of the data item. See 3.14 IDs for details. src: Gives the location from which the data object should be fetched. See Legal Data Values and Value Expressions for details. expr: Evaluates to provide the value of the data item. See Legal Data Values and Value Expressions for details.

40 Datamodel Variables are declared and initialized in a specific section id: The name of the data item. See 3.14 IDs for details. src: Gives the location from which the data object should be fetched. See Legal Data Values and Value Expressions for details. expr: Evaluates to provide the value of the data item. See Legal Data Values and Value Expressions for details.

41 Datamodel Label is any string and expr any legal ecmascript expression (if no expression, needs to be )

42 Datamodel

43 Datamodel What do you think?

44 Guarded transition cond: is evaluated after each micro step and fired when the condition holds

45 Guarded transition

46 Guarded transition QtCreator and SCXML more generally consider the time to be the physical wall clock time. It is obviously not the case for all timed (and critical) systems for which symbolic reasoning is done