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Dynamic Component Composition for Functionality Adaptation in Pervasive

EnvironmentsN. Belaramani, C.L. Wang, and F.C.M. Lau

The Systems Research Group

Department of Computer Science & Information Systems

The University of Hong Kong

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Overview Mobile & Pervasive Environments

Undeniable emerging trend

Main Requirement in Mobile & Pervasive Computing: Software must be able to adapt dynamically

Functionality Adaptation One of the most versatile adaptation techniques Makes software very dynamic

Our Solution: Dynamic Component Composition

Software is assembled at run-time

Facet Model & Sparkle System Illustrates the feasibility of dynamic component composition in a mobile pervasive

environment

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Pervasive Environments Advances in Wireless technology

Bluetooth1-2Mpbs

Wireless Lans54Mbps GPRS

114kbps

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Pervasive Environments Gadgets with wireless connectivity

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Pervasive Environments Lots of mobile devices

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Pervasive Environments Lots of Users

Worldwide Mobile Terminal Sales 2001 – 412 Million2002 – 425 Million2003 – 475 Million2004 – 501 Million2005 – 545 Miliion

(Source: Gartner Dataquest Jan 2003)

Worldwide PDA Shipments2001 – 13 Million2002 – 14 Million2003 – 17 Million

(Source: Gartner Dataquest July 2002)

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Pervasive Environments The Dream:

Pervasive Computing should enable uses to carry out

Computing Anytime Anywhere from Any Device

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Pervasive Environments Still not Completely a Reality

Why? Software architecture is not yet ready

Main Characteristic Heterogeneity and Run-time Change

Device Configurations Network Infrastructure Environmental Factors User Preferences

Main focus for software: Ability to ADAPT

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Adaptation It is the means to change a run-time characteristic in

response to a trigger Change a certain property, parameter or metric

Data Adaptation Network Level Adaptation Energy Adaptation Migration Adaptation Functionality Adaptation

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Functionality Adaptation Computing provides users means to carry out certain tasks

Applications are essentially groups of functionalities which enable users fulfill these tasks.

Functionality Adaptation Adapting the way these functionalities are carried out Changing the execution of the application Most versatile adaptation technique

Example, In cases of bad network conditions, only subject of emails are

downloaded, rather than the whole messages when viewing inbox If less memory is available, a more memory efficient, but requiring

more processing time, algorithm can be used.

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Dynamic Component Composition Applications are made of Components

Brought in from the network, and linked at run-time when they are required

Unlinked and discarded after use.

“GET-USE-THROW”

Application

Components

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Dynamic Component Composition Applications are made of Components

Brought in from the network, and linked at run-time when they are required

Unlinked and discarded after use.

“GET-USE-THROW”Components

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Dynamic Component Composition Applications are made of Components

Brought in from the network, and linked at run-time when they are required

Unlinked and discarded after use.

“GET-USE-THROW”Components

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Dynamic Component Composition “Unlimited” Functionality

Discarding unwanted components frees up resources to bring in other components

Size of the application is not a concern

Intuitive support for functionality adaptation Components suitable for the run-time environment are

brought in Applications are dynamically extensible and adaptable

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Sparkle Mobile Computing System

Facet Query

Facet Retreival

Service Providers

Facet Servers

Co-operative CachingIntelligen

t Proxies

Computational Grid

Execution Servers

Delegation/ Mobiie code

Peer-to-Peer Interaction

Clients

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Sparkle Mobile Computing System Utilizes Dynamic Component Composition in a

Mobile Environment

Applications are made of components – Facets

Each facet fulfills certain functionality

Facets brought in at run-time, executed, then discarded

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Facet Model Functionality

single well-defined task in an application E.g. blurring an image, matrix multiplication

Given a set of inputs, it determines what changes are made and the outputs attained

Contract which specifies Set of input & output parameters Description of what is carried out Pre-conditions and Post-conditions Side effects

In our model, it is identified by a funcID

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Facet Model Separation of functionality from Data and UI

Facets Pure functional units Downloaded to client devices on demand Implement single functionality

single publicly callable method No residual state

Functionality provided by a facet is independent of any previous invocations

Makes it throwable & replaceable at run-time

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Facets Made up of 2 parts

Shadow specifies properties of the facet

General info: facetID, vendor, version Functionality info: funcID Resource requirements: memory, processing, etc Dependencies XML based

Code Segment Executable code to achieve the functionality Does not keep any permanent state

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Facet Request Facet Specification sent to proxy

Functionality, funcID Other criteria such as vendor, version Resource Conditions

Memory, processing power, network conditions

Proxy identifies a suitable facet and sends it to the client matches the criteria with the shadows of the facets available Finds a facet suitable to run under specified resource

constraints

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Facet Dependencies Facets may call upon other facets to achieve their

functionality Note: Functionalities have no dependencies

At run-time, different conditions may lead to different execution trees

p q r

x

i j k i j k

s t

A B A

Cg

fe

x

i j k p q r i j k

x ym n

A B A

FD E

IHG

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Facet Dependencies During execution, facets which are no longer active

can be thrown

p q r

x

i j k i j k

s t

A B A

C

Execution point

Active Facet - currently running

Inactive Facet-already executed completely

Facet whichHas not yet beenBrought in/loaded

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Containers Application-like abstraction

Interacts with the user through the UI

Provides a place to store run-time state

Provides Specifications of the root facets

Check Mail Send MessagePrint Message

Trash Message

Change Font

Facet Spec. 1

Facet Spec. 2

Facet Spec. 3

Facet Spec. 4

Facet Spec. 5

Application Functionalities

Storage Area

Pluggable UI

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Sparkle Client System

Java Virtual Machine

Host Operating System

Facets and Containers

Client System Central Manager

LMCS

Discovery Manager

NetworkHandler

FacetCache

Facet

Resource Manager

Facet Specificatio

n

Find network entity

Location of

Proxy or Peer

SendReques

t

Facet

Migrate

Migration Informatio

nFace

t

Facet

Unload

Facet

GetInfo

Discard Facet

Proxy

Peer

ResourceInformatio

n

Loaded

Facet

Facet Loader

Load Facet

Throw Facet

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Testbed Client System

Compaq iPAQ PocketPC H3870 CPU: 206MHz Intel StrongARM, 32-bit RISC Memory: 32MB RAM + 32MB Flash OS: Familiar Linux v0.5.2 JVM Blackdown-1.3.1-RC1

Proxy Ordinary PC

CPU: Intel Pentium II MMX 300MHz Memory: 128MB RAM OS: RedHat Linux 7.1 Web Server: Apache 1.3.19-5 PPP Deamon: ppd version 2.4.0

Serial Connection 115.200kbps

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Timing Analysis

0

2

4

6

8

10

12

14

16

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0 10 20 30 40 50 60 70

Facet J ar Size (KB)Ti

me

(s)

CheckCache CreateRequest GetFrNetwork CacheFacet

loadFacet CreateInstance Misc TotalTime

Timing breakdown of sending a specification to the client system and receiving an loaded facet and a ready to use instance

Range of facets sizes: JAR: 1KB to 69KB Code Size: 1KB to 500KB

Largest time consumers Getting facets from network

Transmission rate: ~ 80kbps Latency: ~ 2.3 s

Loading the received bytes into JVM and creating instance

Depends on JVM implementation & processing power

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Effect of References We look into the effect of references on performance

Strong references Facets are never discarded Takes more memory

Soft references Discarded by GC

Weak references Discarded by GC

No references Facets in “garbage” as

soon as it is used Saves memory

Result: Not much difference

between strong and soft ref. Weak ref and no ref. have poor performance Not much difference between the different memory configurations

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Per

cen

tag

e o

f To

tal

Req

ues

ts

StrongRef. 4MB

StrongRef.16MB

Soft Ref.4MB

Soft Ref.16MB

WeakRef. 4MB

WeakRef.

16MB

No Ref.4MB

No Ref.16MB

Already Loaded From Cache From Network

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Effect of Caching Investigate if the number of entries of cache has an effect on

performance Soft references were used, heap size 4MB As cache size increases, less requests are directed to the network,

increasing performance

0%10%20%30%

40%50%60%70%

80%90%

100%

Perc

en

tag

e o

f To

tal

Req

uests

NoCache

2 Entry 4 Entry 8 Entry 16 Entry

Already Loaded From Cache From Network

0

50

100

150

200

250

300

350

400

Tim

e T

aken (

s)No

Cache2 Entry 4 Entry 8 Entry 16 Entry

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Image Processing Application To illustrate the feasibility of developing a real-world

application utilizing the facet model

(1) Image Viewer

(2) Menu

(3) Image rendering

(4) Negative

(5) Sizing

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Summary Main Requirement in Mobile Computing:

Software must be able to adapt dynamically to change and variation

Functionality Adaptation One of the most versatile adaptation techniques Makes software very dynamic

Our Solution: Dynamic Component Composition

Software is assembled at run-time

Facet Model & Sparkle System Illustrates the feasibility of dynamic component composition in a

mobile environment

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Contributions Employing Functionality Adaptation (FA) in Pervasive

Computing

Proposed Dynamic Component Composition as a solution to achieve FA

Defined the Facet Model

Illustrated the feasibility and applicability of the facet model

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Related Publications N. Belaramani, C.L. Wang, and F.C.M. Lau, “Dynamic

Component Composition for Functionality Adaptation in Pervasive Environments”, 9th IEEE International Workshop on Future Trends of Distributed Computing Systems (FTDCS 2003), San Juan, Puerto Rico, May 2003.

V.W.M. Kwan, F.C.M. Lau, and Cho-Li Wang, “Functionality Adaptation: A Context-Aware Service Code Adaptation for Pervasive Computing Environments,” 2003 IEEE/WIC International Conference on Web Intelligence (WI 2003), Halifax, Canada, October 2003.

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The End

More information :

http://www.csis.hku.hk/~clwang/projects/sparkle.html