history of its input. □ Characterized by an internal state. • Current state = past
experience. (C) Ludovic Apvrille. UML for Embedded Systems - Fall 2012 slide 6.
UML for Embedded Systems III. Detailed Design Ludovic Apvrille
[email protected] Eurecom, Office 470
Memo on Methodology
IV. Validation of the system Simulation Code generation
III. Detailed design Behavior of the system
I. Analysis Use case First class diagram Relevant scenarios
II. Design Classes of the system Architecture of the system
slide 2
(C) Ludovic Apvrille
UML for Embedded Systems - Fall 2012
Page 1
Detailed Design Stage
slide 3
Purpose • Design the behavior of classes State machine diagrams • Signal sending • Signal receiving • Composite states • Loop, tests • Setting and use of variables • Etc.
(C) Ludovic Apvrille
UML for Embedded Systems - Fall 2012
Detailed Design Basics
of automata Modeling objects with states machines UML state machine diagram TAU G2 state machines Examples
slide 4
(C) Ludovic Apvrille
UML for Embedded Systems - Fall 2012
Page 2
Basics of Automata Definition
• Machines whose input behavior is not only a direct consequence of the current input, but of some past history of its input Characterized by an internal state • Current state = past experience
slide 5
(C) Ludovic Apvrille
UML for Embedded Systems - Fall 2012
Example of State Machine Diagrams
Start state
LampOff
on()
States
off()
Trigger lampOn
slide 6
(C) Ludovic Apvrille
UML for Embedded Systems - Fall 2012
Page 3
Output and Actions Actions
can be generated either at state entrance, exit or at trigger level LampOff
on()/print("on"); off()
lampOn
Mealy automaton
Use of Variables
Integer ctr; LampOff
on()/ctr = ctr+1; off()
lampOn
slide 8
(C) Ludovic Apvrille
UML for Embedded Systems - Fall 2012
Page 4
Mealy Machines
Mealy machines • Hopcroft and Ullman (1979, 42), Salomaa (1973, 31) • Finite-state machines - Take a string on an input alphabet - Producing a string of equal length on an output alphabet.
Formally, a Mealy machine is a six-tuple M = (Q, Σ, Γ, δ, λ, q1) • where - Q = (q1, q2, …, q|Q|) is a finite set of states; - Σ = (σ1, σ2, …, σ|Σ|) is a finite input alphabet; - Γ = (γ1, γ2, …, γ|Γ|) is a finite output alphabet; - δ : Q x Σ → Q is the next-state function, such that a machine in state qj, after reading symbol σk, moves to state δ(qj, σk) ∈ Q - λ : Q x Σ → Γ is the output function, such that a machine in state qj, after reading symbol σk, writes symbol λ(qj, σk) ∈ Γ ; and - q1 ∈ Q is the initial state in which the machine is found before the first symbol of a string is processed
slide 9
(C) Ludovic Apvrille
UML for Embedded Systems - Fall 2012
Example Let
M = (Q, Σ, Γ, δ, λ, q1) with • Q = {q1, q2} • Σ = {sig1, sig2} • Γ = {out1, out2} • δ(q1, sig1) = q1; δ(q1, sig2) = q2; • δ(q2, sig1) = q2; δ(q2, sig2) = q1; • λ(q1, sig1) = out1; λ(q1, sig2) = out2; • λ(q2, sig1) = out2; λ(q2, sig2) = out1; Propose a graphical representation of this machine
slide 10
(C) Ludovic Apvrille
UML for Embedded Systems - Fall 2012
Page 5
Detailed Design Basics
of automata Modeling objects with states machines UML state machine diagram TAU G2 state machines Examples
(C) Ludovic Apvrille
slide 11
UML for Embedded Systems - Fall 2012
What Can be Modeled with State Machines? State
machines are well-suited for the modeling of eventdriven and discrete behavior Inappropriate for modeling continuous behavior
threshold
time Are
State Machines well-suited for modeling real-time and embedded systems? • What is an event-driven systems? • What are real-time and embedded systems?
slide 12
(C) Ludovic Apvrille
UML for Embedded Systems - Fall 2012
Page 6
Event-Driven Behavior Event
= a type of observable occurrence • Interactions - Invocation of object operations is synchronous (call event) - Receiving of asynchronous signal (signal event)
• Occurrence of time instants (time event) - Interval expiry - Calendar/clock time
• Change in value of some entity (change event) Event Instance = an instance of an event (type) • Occurs at a particular time instant and has no duration
slide 13
(C) Ludovic Apvrille
UML for Embedded Systems - Fall 2012
Embedded Systems’ Architecture Embedded
system = controlling system + controlled system + environment Controlling System Sensors Sensors Actuators
Sensors Sensors Sensors
Interface Controlled System slide 14
(C) Ludovic Apvrille
UML for Embedded Systems - Fall 2012
Page 7
Response to External Events External Hostile Environment Synchronous
Synchronous
Asynchronous
Asynchronous
Event (Input)
Embedded System
Response (Output)
Single event
Single event
Multiple event
Multiple event
slide 15
(C) Ludovic Apvrille
UML for Embedded Systems - Fall 2012
What is a Real-Time System? Real-Time
Systems have been defined as: “Those systems in which the correctness of the system depends not only on the logical results of the computation, but also on the time at which the results are produced” (J. Stankovic, “Misconceptions About Real-Time Computing”, IEEE Computer, 21(10), October 1988)
slide 16
(C) Ludovic Apvrille
UML for Embedded Systems - Fall 2012
Page 8
Jobs and Tasks Task
• A task is a set of related jobs joined to provide functions Job • A job is a unit of work, scheduled and executed by the system Parameters • Temporal behavior - Last less than 20ms, periodic task i.e. executes every 30 ms
• Functional: intrinsic properties of the job - Taps of filter
• Resource requirements - 10kb of memory
• Interconnection: its communication with other jobs - The decoding job must send its result to the displaying job - May use shared memory, message queues, etc. slide 17
(C) Ludovic Apvrille
UML for Embedded Systems - Fall 2012
Response to External Events
Timing Constraints
Synchronous
Synchronous
Asynchronous
Asynchronous
Event (Input)
Real-Time RealSystem
Response (Output)
Single event
Single event
Multiple event
Multiple event
slide 18
(C) Ludovic Apvrille
UML for Embedded Systems - Fall 2012
Page 9
Are State Machines Well-Suited for Modeling Real-Time and embedded Systems? What
do you think?
What
should be modeled with state machines?
• In principle, anything that manifests event-driven behavior • In practice: - The behavior of individual objects - Object interactions
The
dynamic semantics of UML state machines are currently mainly specified for the case of active objects
Note:
currently, there is no support in UML for modeling continuous behavior
slide 19
(C) Ludovic Apvrille
UML for Embedded Systems - Fall 2012
Object Behavior: General Model
Initialization
Waiting for input
Note: this is not a UML state machine but rather a flowchart to explain how an object generally behaves
Computing input
Sending output
Termination
slide 20
(C) Ludovic Apvrille
UML for Embedded Systems - Fall 2012
Page 10
Example
Initialization LampOff
Waiting for input
on()/print(on); off()
Computing input
Sending output
lampOn stopLamp()
Termination
slide 21
(C) Ludovic Apvrille
UML for Embedded Systems - Fall 2012
Active and Passive Objects An
active object is a thread of control of the application • Autonomous • No internal concurrency • Mechanisms for storing input data A passive object is an object which is not active • It is activated by external power
slide 22
(C) Ludovic Apvrille
UML for Embedded Systems - Fall 2012
Page 11
Object Behavior: Active Objects
Initialization
Waiting for input
Computing input
Sending output
Termination
slide 23
(C) Ludovic Apvrille
UML for Embedded Systems - Fall 2012
Object Behavior: Passive Objects
Initialization
Waiting for input
Computing input
Sending output
Termination
slide 24
(C) Ludovic Apvrille
UML for Embedded Systems - Fall 2012
Page 12
Passive Objects: Synchronization Issues
Initialization
Waiting for input
Synchronization may be required!
Computing input
Sending output
Termination
slide 25
(C) Ludovic Apvrille
UML for Embedded Systems - Fall 2012
V. Detailed Design Basics
of automata Modeling objects with states machines UML state machine diagram TAU G2 state machines Examples
slide 26
(C) Ludovic Apvrille
UML for Embedded Systems - Fall 2012
Page 13
Basics of UML State Machine Diagrams
States
Transitions s1
Message [condition] / action
s2
Transition with temporal information E1
slide 27
when (date = 10)
(C) Ludovic Apvrille
E1
E2
after(100)
E2
UML for Embedded Systems - Fall 2012
States, Transitions and Actions LampOn entry/lamp.on();
off/printf(“to off”);
LampOff entry/lamp.off();
exit/printf(“exiting”);
exit/printf(“exiting”);
off/printf(“needless”); LampOff entry/lamp.off(); exit/printf(“exiting”); off/null slide 28
(C) Ludovic Apvrille
Self transition entry and exit actions are ignored
UML for Embedded Systems - Fall 2012
Page 14
UML 2.x State Machines: Towards SDL state1
Waiting for the receiving of signal signal1
signal1()
signal2()
Sending of signal signal2
state2
slide 29
(C) Ludovic Apvrille
UML for Embedded Systems - Fall 2012
Guards
state1
LampOff
Integer x;
entry/lamp.off();
signal1()
exit/printf(“exiting”); x = x +1;
on[LampIsPlugged]/printf(“to on”); LampOn
signal2()
x=5
x
