Formal Formal Component Component Models Models for for Context - - PowerPoint PPT Presentation

Formal Formal Component Component Models Models for for Context Context Awareness Awareness

FMCO2008 22.10.2008

Deploy FP7 MatsNeovius andKaisaSere

1 ÅboAkademi– FacultyofTechnology, DepartmentofInformationTechnologies.

Outline Outline of

• fthis

this talk talk

Motivation Informaldefinitions Problem

– Modelling contextawaresystem – Treatingthecontextsascomponents – Treatingthecontextsascomponents – Proposedframeworkforsolvingtheproblem

ActionSystemsataglimpse Contextinactionsystems Example:fictionary driverlesscar Conclusion&furtherwork

2 FMCO2008 22.10.2008 ÅboAkademi– FacultyofTechnology, DepartmentofInformationTechnologies.

Motivation Motivation

• Inordertoproviderigour onSW,formalmethodssuffice

However,inordertoproviderigour onasystem, environmentmustbeconsidered

– Whyisthisofinterest

• forexample,ifthecarbreaksdowntheproblemisnot
• forexample,ifthecarbreaksdowntheproblemisnot

malfunctionedSWorerroneoustreatingofsensor reading,themainproblemis abrokencar.

– Inasystem,theenvironmentisadecisivefactor, weneedtointroduceit“formally”

• Considerirrationalityandforcethedesignertotreatand

includewhichandhowforinstancesensorreadingsare acquiredandcalculatedwith

3 FMCO2008 22.10.2008 ÅboAkademi– FacultyofTechnology, DepartmentofInformationTechnologies.

Informaldefinitions Informaldefinitions

Context (when talking about contextaware)

–

• [Dey,others]

Component

–

• [Szyperski]

4 FMCO2008 22.10.2008 ÅboAkademi– FacultyofTechnology, DepartmentofInformationTechnologies.

Problem Problem – modelling

modelling a acontext context aware aware system system

Howisanelementarycontextutilised in thecontextawareSW

(Elementarycontextdenotesforinstanceasensorreading)

– Needtospecifythe”utiliserinterface” – Needtospecifythe”utiliserinterface”

Howiscontextprocessedtoprovide increasedinformation

– Compositionofelementarycontexts – Needtospecifytheinterfacebetweenthe processingentities

5 FMCO2008 22.10.2008 ÅboAkademi– FacultyofTechnology, DepartmentofInformationTechnologies.

Problem Problem – Treating

Treating contexts contexts as ascomponents components

Avoidamonolithicconstructionsforthe sakeofindependentdeploymentandreuse Informationbuildsbottomup

– Elementarycontextsformthebasisfor – Elementarycontextsformthebasisfor contextawareSW

• Compositionofcontexts

6 FMCO2008 22.10.2008 ÅboAkademi– FacultyofTechnology, DepartmentofInformationTechnologies.

Accelerate ok(given speeding isprohibited)? acquire :velocity∧ speed_limit improve :velocity >speed_limit → speeding :=true provide :speeding

Problem Problem – solution

solution

Treatcontextasaservicetoitsutiliser

– Utiliser abletoacquireinformation wheneverdesired(triggeredbysomething, maybeacontext) maybeacontext)

• Suchaswhenresolvingwhetherornotto

accelerate(previousslide)

– Weconsidereachsocalledelementary contextasacomponentinitsownright

7 FMCO2008 22.10.2008 ÅboAkademi– FacultyofTechnology, DepartmentofInformationTechnologies.

Problem Problem – solution

solution view view

Contextutiliser /application

– Reliesonsomecontextservice(s)

• Proactive(orreactive)

8 FMCO2008 22.10.2008 ÅboAkademi– FacultyofTechnology, DepartmentofInformationTechnologies.

Problem Problem – solution

solution view view

Contextutiliser /application

– Reliesonsomecontextservices

• Proactiveorreactive

Contextservice

– Reliesonasetofcontextprocessors – Reliesonasetofcontextprocessors

• Providesananswertosomequestion

9 FMCO2008 22.10.2008 ÅboAkademi– FacultyofTechnology, DepartmentofInformationTechnologies.

Problem Problem – solution

solution view view

Contextprocessor

– Atriad,CD||CI||CP

• CD– acquiremetrics
• CI– applyalgorithm
• CP– provideametricwhoseinformationhavebeenincreased
• CP– provideametricwhoseinformationhavebeenincreased

10 FMCO2008 22.10.2008 ÅboAkademi– FacultyofTechnology, DepartmentofInformationTechnologies.

Problem Problem – solution

solution view view, ,all all together together

Inspired by: Henricksen andIndulska,”Modelling andUsing Imperfect Context Information”,CoMoRea 2004. Shehzad,Ngo,Pham,Lee”Formal modeling inContext aware systems” CAMUSframework andContextual informtaion hierarchy 11 FMCO2008 22.10.2008 ÅboAkademi– FacultyofTechnology, DepartmentofInformationTechnologies.

Action Actionsystems systems ata ataglimpse glimpse

Statebasedformalism,basedonDijkstra’s guardedcommandlanguage

– Apredicate(guard)enablesastatement (body)g→ S (body)g→ S

• Atomicity
• Nondeterminism
• Parallelism

12 FMCO2008 22.10.2008 ÅboAkademi– FacultyofTechnology, DepartmentofInformationTechnologies.

=|[ import imp_list; export exp_list :=e0; var var_list :=v0; proc list ofpr.name (par.name.list)=<{impl}>; dog1 → S1[]…[]gn → Sn od ]|

Specialisations Specialisations ofaction

• factionsystems

systems

Contextisnonchangeable

– Newdeclarationsof

• read_only :publishedbysomeotherAS
• publish:read_only inotherAS
• publish:read_only inotherAS
• context:elementary

context(s)

13 FMCO2008 22.10.2008 ÅboAkademi– FacultyofTechnology, DepartmentofInformationTechnologies.

ℬ =|[ context c import j; export f :=f0; read_only r; publish p:=p0; var w:=w0; proc ; dog1 → S1 []…[]gn → Sn od ]|

Specialisations Specialisations toaction toactionsystems systems cont cont

Introducingcontextintheutiliser @

– Def.@:g1 → S1@=g1 ∧ g → S1; S where g andS isdefined inactionsystem interface – Actionsystem

• ℬutiliser =|[
• – Actionsystem

interface function as theinterface forthe context service (relying oncontext processors)

14 FMCO2008 22.10.2008 ÅboAkademi– FacultyofTechnology, DepartmentofInformationTechnologies.

ℬutiliser =|[ import j; export f :=f0; var w:=w0; proc ; dog1 → S1@T []…[]gn → Sn …od ]|@interface

Specialisations Specialisations toaction toactionsystems systems cont cont

Introducingcontextintheutiliser @

– Def.@:g1 → S1@=g1 ∧ g → S1; S where g andS isdefined inactionsystem interface

• =|[

ℬutiliser =|[

15 FMCO2008 22.10.2008 ÅboAkademi– FacultyofTechnology, DepartmentofInformationTechnologies.

interface =|[ read_only rr; import ir; export er; var vr; procProc_name (par.name.list) ={<impl>}; do… T: gT →ST

• d |]

ℬutiliser =|[ import j; export f :=f0; var w:=w0; proc ; dog1 → S1@T []…[]gn → Sn …od ]|@interface

A Acontext context processor processor – making

making information information

ℐ =|[contextε; importλ; read_only x; exportq; publishy; var b; procnonce(x)=f (x):x’; ≔ =|[contextε; importD; read_only y; exports; publishz; var h; proc ; ≔ =|[contextc; importϕ; read_only m; exportt; publishx; var a; proc ;

16 FMCO2008 22.10.2008 ÅboAkademi– FacultyofTechnology, DepartmentofInformationTechnologies.

procnonce(x)=f2(x):x’; do ω→y≔ f1(nonce(x))λ []¬ω →V []γ

• d

]| proc ; do ψ →z ≔ f(y) []¬ψ →U []δ

• d

]| proc ; do g →S (x :=E) []¬g →T []β

• d

]|

A Acontext context processor processor

composed composed Composition possible assuming

– Thelocal variables are disjoint

||ℐ|| =|[ contextc ⋃ ε; import(ϕ ∪ λ∪ D \ e); read_only m; exporte :=t ∪ q ∪ s; publishz; ∪ ∪ ∪ ∪

17 FMCO2008 22.10.2008 ÅboAkademi– FacultyofTechnology, DepartmentofInformationTechnologies.

∪ ∪ publishz; var v:=a ∪ b ∪ h ∪ x ∪ y; procnonce(x)=<{impl}>; … do β[] γ []δ[]T[]V[]U[]B1 [] B2 []…[]Bn;

• d

]|

Example Example: :non non speeding speeding car car

Asmartcarthatdoesnotallow accelerationifspeeding

– Demandscomparisonofvelocityvs. speedLimit speedLimit

• Seeminglyeasybutwhatisneededtocalculate

velocity(assumingspeed limit isclear cut)

– velocity = (wheel_height,wheel_rpm,π)

18 FMCO2008 22.10.2008 ÅboAkademi– FacultyofTechnology, DepartmentofInformationTechnologies.

Example Example:the :thecontext context utiliser utiliser

istheutiliser isthe contextinterface

– g → S callsonaction labled Acc in – ActionAcc calls on

=|[import j; export f :=f0; read_only ; var w:=w0; proc ; do A []g →S @Acc[]…[]A

• – ActionAcc calls on

resolving procedure speeding – According to definitionof@, g → S = g ∧ g→ S ;S

19 FMCO2008 22.10.2008 ÅboAkademi– FacultyofTechnology, DepartmentofInformationTechnologies.

A1 []g2→S2@Acc[]…[]An

• d ]|@

=|[ procSpeeding(vel:Int,spLi:Int)= vel ≤spLi →return:=true read_only velocity,speedLimit; var vel ≔ velocity,spLi ≔ speedLimit; do … Acc:Speeding(vel,spLi)=true→skip

• d ]|

Example Example: :making making velocity velocity

Contextprocessorℰ publishes and calculatesitgiventhat

– wheel_rpm,rim_dia

ℰ||ℐ|| =|[… context c; publishvelocity; read_only k; var v; … ProcCalcVel(rpm:Int,rim:Int,tyre:Int)

andtyre_height is providedbyread_only

• rbysensed

elementarycontexts (̟isaconstant)

• wheel_rpm,rim_dia,

tyre_height ∈ {k∪ c}

20 FMCO2008 22.10.2008 ÅboAkademi– FacultyofTechnology, DepartmentofInformationTechnologies.

ProcCalcVel(rpm:Int,rim:Int,tyre:Int) =v:=rpm*π*(rim+tyre) do CalcVel(wheel_rpm,rim_dia, tyre_height)→ velocity ≔ v; …

• d

]|

Conclusions Conclusions

Conclusions

– Each elementary context istreated asa component

• Specified interface
• Independently deployed
• Independently deployed
• Composed by third parties

– Wehavegivenaformalsyntaxforthisandshowed therelevanceandimplicationofthis

• With anexample
• Motivated with words – remember thebroken car

21 FMCO2008 22.10.2008 Åbo Akademi – FacultyofTechnology, DepartmentofInformationTechnologies.

Future Future work work

Futureworkinthiscase

– Howdoesthisrelatetorefinement

Futureworkonamoregenerallevel

– Canwetreatcomposedcomponentsinseparationand whatcanwetellaboutthem whatcanwetellaboutthem – Canweformallymodelonlyasubsetofasystemand whatcanwesayaboutitinthatcase

22 FMCO2008 22.10.2008 ÅboAkademi– FacultyofTechnology, DepartmentofInformationTechnologies.