Outline AIMS Embedded Systems Programming MT 2015aims.robots.ox.ac.uk/wp-content/uploads/2015/11/7-uml-2x3.pdf · What is UML? I TheUnied Modeling Language(UML) is a standardized

AIMS Embedded Systems ProgrammingMT 2015

Design with the Unified Modeling Language (UML)

Daniel Kroening

University of Oxford, Computer Science Department

Version 1.0, 2014

Outline

D. Kroening: AIMS Embedded Systems Programming MT 2015 2

Model-Driven Architecture (MDA)

Model-Driven Architecture

Key idea:1. Build high-level model for the software

system2. Gradually refine into actual program

while maintaining a layered architecture

MDA is forward engineering: the specification comes before theimplementation


Technology Independence

Requirement: Preserve investment in an application

I as platforms proliferateI while the existing platforms change

Solution: Isolate information and processing logic fromtechnology specifics

I Build platform-independent modelsI Refine these models to specific platformsI Maintain this separation


Raising the Level of Abstraction

I Not new. Has been done before.I Programming Languages

(hardwired circuitry, punch cards, assembler, PASCAL/C,OO, ...)

I Operating systems, data bases, ...

I Interesting: well-established for two sides of the problemI WYSIWYG GUI buildersI Data modeling

→ hand coding no longer predominates

I Goal: higher productivity


MDA Models

Business Model(computation-independent)

PPPqAnalysis Model

(platform-independent)PPPq

Design Model(platform-dependent)

PPPq

Code

RE

FIN

EM

EN

T

BUSINESSANALYST

ARCHITECT/DESIGNER

DEVELOPER/TESTER


What is UML?

I The Unified Modeling Language (UML) is a standardizedlanguage for describing software

I graphical notation for all constructs

I Focus on object-oriented systems

I Dominating language for modelling application software(2nd only to English)


History

I Grady Booch, Ivar Jacobson, and James Rumbaugh, atthe time employed at Rational Software:

1990s: UML 1.x

I November 1997: UML became a standard,defined by the Object Management Group (OMG)

I September 2004: UML 2.0


Why?

1. You are very likely to see this on the job!

2. It’s the standard for OO design

3. (Some) formalization possible,enables tool-support


UML Diagram Types

THIS COURSE

Structure

Behavior

Diagram

DeploymentPackage

InteractionUse Case

ActivityState Machine

ClassComposite StructureObjectComponent

Timing

Overview

CommunicationInteraction

Sequence


Disadvantages of UML

I Semantics is vague: meaning of diagrams is not alwayswell-defined

I Some historical, inherited complexity

I Huge (main standard document has 732 pages),and not very accessible

I Tools assign different meanings to the same diagram


Class Diagrams

A Class Diagram...

describes the types of theobjects, and relationshipsamong objects

Studentname: Stringcollege: Collegefriends: Person[0..*]courses: Course[0..*]supervisor: Academicenroll(Course c): voiddrop_out(Course c): void

I Classes have a name and twomore compartments

I 1st compartment: fieldsI 2nd compartment: methodsI Classes belong to a package.


Packages

XYZ

XYZ.SUB


PersondateOfBirth : Datename : StringchangeName(...) : boolean


PersondateOfBirth : Datename : StringchangeName(...) : boolean I These form a

namespace.

I The arrowdenotes“contained in”


Class Fields


I These are variables, and hold thestate of the object

I Fields have aI name, and aI type.

I The type may beI a class,I or something “predefined”.I Arrays are also possible using

multiplicities – we will discussthe syntax later.

I Static fields are underlined.


Initial Values

ConstantsPI: Real = 3.14159265 {readOnly}e: Real = 2.71828183 {readOnly}speed_of_light: Real = 299792458Plancks_constant: Real = 6.62606896E-34

I Fields may have an initial valueI Syntax:

field name : field type = value

I These are assigned upon creation ofthe object→ constructor


Methods

String_size: Integersize(): Integerconcat(s: String): Stringsubstring(lower: Integer, upper: Integer): StringtoInteger(): IntegertoReal(): Real

I Operations that have read/write access to thefields

I Defined byI name,I parameter list,I return type.

I It is possible to define operators as well.


Modifiers: Example

Patient*-dateOfBirth : Date*+treatment : String*#illness : String*+name : String*~GP : Number*+updateCondition( condition : ConditionCode, Notes : String ) : void*#changeName( newName : String ) : boolean*#printPrescription() : boolean*+notifyGP() : void

+ public − private# protected ∼ package


Relationships between Classes

I Generalization

I Association

I Aggregation

I Composition


Generalization

Patienttreatment : Stringillness : StringGP : NumberupdateCondition(...) : void


I Taxonomic relationshipbetween a more generaldescription and a morespecific one that extends it

I OO: this is inheritance

I denoted by an arrow line withan empty arrowhead fromsubclass to superclass

I Often: read as “is a”


Generalization: Example I

Patienttreatment : Stringillness : StringGP : NumberupdateCondition(...) : void


Doctorspecialities: Speciality[0..*]


Generalization: Example II

StoryGenre: String

BookISBN : Stringpublisher : Stringpages : Integer

Novel

This is multiple inheritance!1

1Read Bertrand Meyer, “Harnessing multiple inheritance”, for more on this.D. Kroening: AIMS Embedded Systems Programming MT 2015 21

Association

I “Connection” between classes (may involve more than two)

I Class X uses/references class Y

I This connection may have several properties:I NameI NavigabilityI MultiplicityI Role names, visibility

I Denoted with a solid line


Properties of Associations

I NameI Typically a verbI Describes nature of connection

I NavigabilityI Establishes the direction of the relationI Denoted with an arrow headI May be bidirectional or unspecified

I MultiplicityI Establishes how many objects participate in the relationI Typical: 0, 1, 0..1, 1..∗, 0..∗ (same as ∗)I Default: 1

I Role names, visibility→ think of these as extra members


Association: Example I

Customer Magazinesubscribes0..* 0..*+subscriber +subscribed magazine


Association: Example II

Professor Studentsupervises1..2 0..*+supervisor +student


Association: Example III (Navigability)

Studentname: Stringcollege: College

Mark


n-Ary Relations

Some cases associations involve more than two classes

Student Course

Grade

0..*1..*

0..*

I A student takes zero or morecourses,and possibly has grades

I A course has at least onestudent,and possibly has grades (for thestudents)

I A grade may have been obtainedby at least one student, and maybe assigned to some courses


n-Ary Relations: Another Example

Teamname: String

Score

Matchstadium: String

1..*2

1


Aggregation

I Special case of association

I Read as “has a”

I Must not involve more than two classes

I Not a container relationship – no implications on lifetime

I Drawn with empty diamond


Aggregation: Example

Professor Courseteaches 0..*+teacher +course


Composition

I Special case of aggregation

I This is a container relationship:once the “owner” is destroyed, so is the object containedtherein

I “Owner” must have multiplicity 0..1 or 1

I Drawn with a filled diamond


Composition: Example

Triangle Point3


Templates

VectorTsize:int

I Classes may have templateparameters

I Corresponds to C++ templatesor Java generics

I Build an instance with Vector〈int,3〉


Object Diagrams

S1: Studentname=’’John Smith”

I These are instances of classes

I Look like class diagrams,but the name is underlined

I The second compartmentcontains initializations


Behavior Diagrams

I So far, we only saw Structure Diagrams

I No behavior on those defined so far – even the methodsare somewhat mysterious

I We will now look at Behavior Diagrams:I Use Case DiagramsI Activity DiagramsI State Machine DiagramsI Sequence Diagrams


Use Case Diagrams

A Use Case Diagram...

is a description of system behavior withrespect to external entities such as humanusers or other systems.


Use Case Diagrams

Student Professor

Teaching

There areI use cases (ovals): these correspond to behavior.

I actors (stick figures)

These diagrams are really informal.


Use Case Diagrams: Use Case Extension

Student Professor

Teaching

Tutorial Class Lecture

I Use cases can be specialized/extended

I This is like inheritance – same notation


Use Case Diagrams: Actor Extension

Student Professor

Teaching

BSc Student MSc Student

I Actors can be specialized/extended

I This is also like inheritance


Activity Diagrams

study

eat watch TV

still interested

had enough

I There is a notion of an activecontrol location (the nodes)

I Change in semantics fromUML 1.x to 2.x!

I UML 2.0: Rounded boxes areactivities,semantics similar to Petri Nets


Activity Diagrams: Building Blocks

Initial node

Activity final node

Flow final node

Conditional branch (somewhat redun-dant)

Merge (also redundant)

Fork: concurrency!

Join: process synchronization


Semantics of Activity Diagrams

study

eat watch TV

still interested

had enough

vfvf

vfvf

vf vfvf vf

vf

I Idea: pass tokens around

I Forks replicate tokens,join nodes generate tokens ifthere are enough incomingtokens.

I Formalization: class assignment


Activity Diagrams: Branches and Guards

I Guards should not overlap – theordering of evaluation is not defined

I The guards should be complete

I One of the edges may have a guard else


State Machine Diagrams

A State Machine Diagram...

is a graphical representation of a finite statemachine.

On

Off

I These are a variant of Harel’sstatecharts (1987)

I Very popular in control engineering(automotive, aerospace, ...)

I Also see Martha’s Executable Biologycourse


State Machine Diagrams: Building Blocks

Initial / Junction

Terminate

Entry Point / Exit Point / History (hier-archy)

Choice (somewhat redundant)

Fork

Join

trigger [guard] / action Transition with trigger, guard, and ac-tion


State Machine Diagrams: Warmup Example

Twiddle thumbs

i=0

[i<10]/i++

[i>=10]


Transitions in State Machine Diagrams

Trigger, ... [ Guard ] / Action

I Each part is optional

I A Trigger is typically an event identifier with arguments:Event ( Recv-Arguments . . . )

If there is more than one trigger: OR-semantics

I The Guard is a Boolean expression

I An Action can beI some assignment, function call,I a send-event command. Typical syntax:

Event ( Send-Arguments )


Branches and Guards in State Machine Diagrams

I Guards should not overlap – the ordering of evaluationis not defined by the standard

I The guards need not be complete: you just stay in thecurrent state until a transition becomes enabled


Events in State Machine Diagrams

I Idea: there is a finite set of events;events may be parameterized, e.g., button(1)

I Events may be external or internal

I There is a queue of events that have occurredI The ordering of dequeuing is not defined

I The processing of an event must be finishedbefore any other event is processed (run-to-completion)


Events in State Machine Diagrams: Example

Start Dialtone Dialing Busy

Wrong Number

Busy

Ringing Connected

Pick up Dial(d) RecBusy

RecPickup

Hang up

Hang up Hang up Hang up

Hang up

Hang up

Timeout

WrongNr

GoodNr

I Those plentiful “Hang up” edges are annoying

I What about dialing more than one digit?


Internal Transitions in State Machine Diagrams

DialtoneDial(d) / nr+=d

DialingDial(d)/ nr+=d

I Internal transitions are triggered only if the state containingthem is active

I May have triggers, guard, action

I They fire without leaving/re-entering the state


Internal Actions

States may have special internal transitions defined using thefollowing prefixes:

I entry: executed when a state is entered

I exit: executed when a state is left

I do: ongoing activity while in the state


Hierarchy in State Machine Diagrams

Outer State

Inner State 1

Inner State 2

I State machines may be nested,which yields hierarchy

I Transitions may cross hierarchyboundaries

I Advantage: May avoid manytransitions

I Hierarchy may be used to modelconcurrency


Hierarchy in State Machine Diagrams: Example

Phone off the hook

Dialtone Dialing

Ringing

Busy

Wrong Number

Connected

Pick up

Dial(d) RecBusy

RecPickup

Timeout

WrongNr

GoodNr

Hang up


Hierarchy in State Machine Diagrams: Example

Phone off the hook

Dialtone Dialing

Ringing

Busy

Wrong Number

Connected

Pick up

Dial(d) RecBusy

RecPickup

Timeout

WrongNr

GoodNr

Hang up


State Machine Diagrams: History

Student Life

SleepEat

StudyPlay

Wait outside of building

Fire Alarm All Clear

I We have seen thathierarchy is useful tomodel exceptions

I But how about recovery?

Sometimes it is helpful toresume what youinterrupted.

I This is modelled by meansof a history node.


State Machine Diagrams: History

I A transition to a history state restores the state that thechart was in when it was left.

I This is meant to be used as means to resume an activityafter an exception or the like.

I There may be one transition outgoing from a history state –this goes to the default state.

I There is also a deep history state:I Denoted by H∗

I Also restores the state of any sub-charts,e.g., within “Sleep” or “Eat”.


Precedence Rules for Transitions

I What if multiple transitions are enabled?Which one is taken?

I There is only one rule:

UML Transition Precedence Rule

A transition out of a composite state s has a lowerprecedence than any transition out of anysub-state of s.

I This applies to UML State Machine Diagrams – Statechartdialects have all sort of additional rules.


Concurrency in State Machine Diagrams

I You can use to obtain concurrent threads ofexecution

I There is an alternative, which is easier to manage

I There are both and-states and or-states in state charts

I or-states are what you are used to:you either “Eat” OR “Sleep” OR “Play”. . .

I and-states allow you to “Eat” AND “Play”


Concurrency Example

Taking a Course

Practical 1 Practical 2 Practical 3 Practical 4

Class 1 Class 2 Class 3 Class 4

Exam

PassFail

fail

pass

I Concurrent threads denoted by means of “swimlanes”I Composite activity ends once all composed activities end


Sequence Diagrams

A Sequence Diagram...

defines the behavior of objectsby describing the messagesthey pass.

Mike John

How are you doing?

Good, and you?

I Horizontal axis: the objects oractors

I Vertical axis: time


Sequence Diagrams: Building Blocks

Mike: PersonObject with type and lifeline

i++ Synchronous message

i++ Asynchronous message

return Return from method

Control


Notation for Messages

1: hello Messages can be numbered

2: buy(”tuna sandwich”) Messages can have parameters

Messages can be self-referential


Synchronous vs. Asynchronous Messages

Synchronous: The caller waits for the completion of the ex-ecution of the operation

Asynchronous: The caller does not wait for the completionof the execution of the operation, but insteadcontinues immediately


Lifetime vs. Control

A

B

foo(1,2,3)

A

B

foo(1,2,3)


Sequence Diagrams: Webshop Example

Client Webshop Mastercard

‘‘BUY(card, product)”

‘‘AUTHORIZE(card, amount)”

‘‘RESULT(status)”

‘‘BUILD_PAGE(status)”


Semantics of Sequence Diagrams

I A sequence diagram defines a partial ordering on the timean event (send/receive) occurs.

I Rules (causal order):

1. Send before matching receive2. Receive or send before send of same process3. Two receives on the same process sent from the same

process

WARNING:

No other guarantees provided,even if suggested by diagram!


Races in Sequence Diagrams

AB

I Let ≺v be the visual ordering,and ≺c the causal ordering

I A diagram has a race iff there existsa trace M1, . . . ,Mn with

M1 ≺c M2 . . . ≺c Mn

but not

M1 ≺v M2 . . . ≺v Mn


Sequence Diagrams: Webshop Example Again

Client Webshop Mastercard

‘‘BUY(card, product)”

‘‘PLEASE_WAIT’’‘‘AUTHORIZE(card, amount)”

‘‘RESULT(status)”‘‘BUILD_PAGE(status)”


Combining Sequence Diagrams

Meeting

Mike John

How are you doing?

Good, and you?

Sequence diagrams can becombined or integrated intoother diagrams by adding aframe


Combining Sequence Diagrams

C1

P1 P2

A

B

C2

P1 P2

C

C3

P2 P3

D

These are calledHigh-levelMessageSequence Charts(HMSCs)

Does this onehave a race?


Documents

Outline AIMS Embedded Systems Programming MT 2015aims.robots.ox.ac.uk/wp-content/uploads/2015/11/7-uml-2x3.pdf · What is UML? I TheUnied Modeling Language(UML) is a standardized