Ubicom Ch07 Slides

7/22/2019 Ubicom Ch07 Slides

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UbiCom Book Slides

1Ubiquitous computing: smart devices,environments and interaction

Chapter 7Context-Aware Systems

(Part A: Contexts & the Context-Aware Lifecycle)

Stefan Poslad

http://www.eecs.qmul.ac.uk/people/stefan/ubicom


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Chapter 7: Overview

Chapter 7 focuses on:

Internal system properties: context-awareness

External interaction with any type of environment

Focussing more on physical environment

A lesser extent focussing on ICT environment

Ubiquitous computing: smart devices, environments and interaction 2


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Related Chapter Links

Context-awareness of human environment (iHCI) andperson-awareness and user context acquisition (Chapter 5)

Environment context acquisition: sensors (Chapter 6)

Environment context control: controllers (Chapter 6)

Event-based system models for context-awareness(Chapter 3)

Goal-based models & sequential environment models

(Chapter 8)

Content adaptation for mobile terminals (Chapter 4)

UI techniques adapted for use in small and large displays

discussed (Chapter 5)



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Chapter 7: Overview

The slides for this chapter are also expanded and split into

several parts in the full pack

Part A: Contexts & the Context-Aware Lifecycle

Part B: Context Adaptation Design

Part C: Spatial Awareness 1

Part C: Spatial Awareness 2

Part E: Mobile Awareness

Part F: Temporal Awareness & Composite Context

Awareness



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Lecture Outline

Types of Context and Context Properties

Context Aware Life Cycle

Context Adaptation

Spatial-Awareness

Mobile User Context Awareness: Call Routing

Content Adaptation for Mobile Terminals

Temporal awareness

Composite Context Awareness



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6Ubiquitous computing: smart devices, environments and interaction

Smart (Physical) Environments

Physical

Environment

Devices Context-aware

Physical

Environment

Context Types

CPI

Structure

Human ICT

Location-

aware

GIS

Location

Sensoror Tag

Device

Display

Content

adaptation

Mobile

aware

Personalisation

Time-

aware

Self-aware

iHCIHomogeneous

SingleAttribute

MultipleAttribute

Life-Cycle

Single Multiple

Heterogeneous

Control

Sense

Adapt

Active

Passive

Operation

Acquire

User

Acquire

Env.

Manage

Present

Process


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Context Aware System versus Sensor-

based System



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Contexts

A context represents the state or situation in theenvironment of a system that affects that systems

(application specific) behaviour

There are many definitions of context

There are several dimensions or properties tocharacterise contexts

There are many definitions of how to make systems

aware of changes in their context: context awareness

Context-awareness is considered to be one of thefundamental properties of UbiComp systems and is a

key property of smart environments.



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Defining Contexts: Concrete

In terms of membership of some set of contexts Location, identities of nearby people, objects and changes

to those objects

Applications

External environment: physical, human, virtual Awareness of internal (self) context may also be useful

What, who, where, when, how it is accessed and why,

context is useful (Morse et al. (2000)



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Context Types: By Application

We can classify context-awareness in terms of types ofapplications?

Mobility context-aware

Location aware

Time aware



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Lecture Outline

Types of Context & Context Properties

Context Aware Life Cycle

Context Adaptation

Spatial-Awareness Mobile User Context Awareness: Call Routing


Temporal awareness Composite Context Awareness



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Life-cycle for Context Awareness

Capture Physical Context Capture User Context

Context Processing

Adapt to Context

Manage contexts



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Configuration

Actuators

Sensors

Environment

Abstraction

Display

User Tasks

Events

UserContext

Context

Store

Store /Retrieve

Annotated Content

AdaptedContext

Control

Adaptation

User EnvContextMediationEnv Context

Composition

Context Processing

& Adptation

Environment (Env)Context Creation

Non-adaptedContext

Access

Control

Annot-ation

Context Management

Application

User ContextCreation

ContextControl

Access

Context Filter

Policies

Context

Discovery

Discovery


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User Context Creation

Acquisition of user context: this can be derived from usersapplication tasks

Policy creation: created from users tasks to determine howa user context is mediated by environment contexts

Encapsulation and abstraction: of the user context

Sharing the user context so that it can be distributed and

accessed.



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Environment Context Creation / Capture

Acquisition:

Encapsulation:

Abstraction:

Filtering:

Sharing:



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Context Processing

N.B Context acquisition may involve some context pre-processing, here the focus is on context post-processing.

Context post-processing enables:

Context-composition:

Context Mediation: Context Adaptation:



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Context Composition: Motivation

Context composition may also be driven by the need to: Improve acquisition accuracy for the context

Improve filtering and adaptation of content

Composite contexts are in inherent an application



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Context Composition: Challenges

Handling heterogeneity of representation Handling heterogeneity of meaning

Mediating and coordinating context aggregation

Ordering the adaptation to individual contexts

Different weightings for combining contexts

Handling uncertainty in combining contexts



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Context Composition, Heterogeneous

Contexts & Interoperability

Context-aware systems may depend on & combine: multiple representations for a single context

.

multiple representations of multiple contexts

Multiple representations determined independently by

different applications & users



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Context Composition, Heterogeneous

Contexts & Interoperability

Determination of a proposed joint context for meetingcan be complex

Challenge here: to harmonize or standardize annotation

so that they would be consistent used by all users.

Security, e.g., access control could be useful in certain

applications to protect privacy or to limit access,



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Context Management

Discovery: directory services enable context sources,stores and users to be registered and discovered.

Storage: of context data into some data resource, may

include

Sharing of environment and goal contexts

Access control:

.



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Lecture Outline

Types of Context and Context Properties Context Aware Life Cycle

Context Adaptation

Spatial-Awareness



Temporal awareness




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Context Adaptation: Passive vs Active

Passive context adaptation system Context is presented to users

Context-based tagging (chapter 6)

System is not active in terms of adapting

Active context-adaptation system Adaptation to context performed by the UbiCom system, not human

users.

Hybrid context adaptive system

Human user guides or corrects the automatic adaptation



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Context Adaptation Models

Event-based Models (Chapter 3) Context-awareness links context producer to a context-

consumer or context-adapter

EDA is also similar to a Reactive intelligent system

See Chapter 8

How do we limit the types of interest?

Goal-based Models

Use a (planned) application or user goal to limit the set of

current contexts which are useful Relation of current context to goal context is

fundamental



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Context-aware Application: Location

(context) awareness

Goal

context

Current

context Context

Path

Constraints

Travel to the destination

location

Current location

Planned path from the current

to destination location

Not to deviate too far from theanticipated or planned position

context;

Ubiquitous computing: smart devices,environments and interaction

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Context-aware Application: Location

(context) awareness


Start Context

Move Forward

Context Deviation

Planned Current Context

Move To SideRe-plan & Move forward

Goal Context Planned Current Context

start

Context Deviation

Move To Side


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Context Aware Design Issues

Context Representation Use of Current versus Past Contexts

Context Determination

Static versus Dynamic CA

Active versus Passive Context Adaptation (done)

Heterogeneous Contexts & Interoperability

Context Composition



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Context Representations

What type of data structures should be used to modelcontexts?

Key-Value pairs

Hierarchies / Markup Schemes, e.g., XML

Graphs Object Oriented (o-o)

Logic Based: support reasoning about context

Strong Ontology

Which of these is best? Why?



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Use of Current Context vs. use of

Context History

Simplest type of context-aware system Uses the current context, the current state, episodic, environment

Operates in an environment that is fully observed and deterministic

But context history can also be used

See Chapter 8 for more in-depth treatment of environments


CA Design issues: Context


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CA Design issues: Context

Determination

Context determination: acquisition, accuracy particularly ofuser context can be complex

Active versus passive context acquisition

Single shot (static) versus dynamic acquisition

Heterogeneous context representation (syntax) andsemantics, interoperability

Context distribution: Local context producer but remote

context consumer



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User Context Determination

4 approaches

Combine several low-level sensor inputs to better infer user

context,

Can Query user profile or model: abstraction thatcharacterises the user, preferences the user expresses,

Ask users to define their own context.

Observing user interaction



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Static versus Dynamic CA

Static environment context

Dynamic environment context:



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Context Adaptation Benefits

Many useful Applications:

Reduces information overload on users

Lessen cognitive load on users

Filter information to fit a mobile device's limited and

physically moving display,

Disabled people

Improve Regulation & Control



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Context-awareness: Challenges

1. User Contexts may be incorrectly, incompletely, impreciselydetermined or predicted, ambiguous

2. Environment Contexts may be incorrectly, incompletely, imprecisely

defined, determined or predicted.

3. Contexts may exhibits a range of spatial-temporal characteristics

4. Contexts may have alternative representations 5.Contexts may be distributed and partitioned, composed of multiple

parts that are highly interrelated

6. Contexts may generate data huge volumes

7. Context sources and local processes often need to embedded in a

low resource infrastructure

8. Context use can reduce the privacy of humans

9. Awareness of context shifts can distract users



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Lecture Outline


Context Adaptation

Spatial-Awareness



Temporal awareness




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Spatial-Awareness Overview

1. Trigger spatial-aware services2. Sense / determine current Location

3. Determine the spatial context

4. Service adaptation: adapt spatial information

view w.r.t. to location



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Spatial-Aware Applications

Applications which trigger use of spatial aware Navigation,e.g., I'm lost, where is nearest Metro station?

Notification of context change: e.g. traffic queue ahead,

change route..

Querying location context, e.g. What speed limit on this road?

Personal Emergency: e.g. medical and Roadside Emergency Service Operations: e.g., Are flammables

nearby?

Enterprise Asset Tracking: e.g. Where is water supply?

Public Asset Trackinge.g. where is the train now? Personal Asset Trackinge.g. I lost my PDA, where is it now?

Location / time based offers,e.g. Free mobile phone calls

while you are in location X

Location & time synchronisation: e.g., ImaHima users37Ubiquitous computing: smart devices, environments and interaction

L ti A S ti l A


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Location-Aware vs Spatial Aware vs

Composite Spatial Aware

Triggering Awareness of a locationa point in 3D space

Awareness of a location in relation to another location

Awareness of a location in relating to its surrounding 2D

space

Composite spatial awareness



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Location Determination Methods

Several common Methods Proximity Analysis

Triangulation

Time Difference of Arrival(TDOA), Multi-lateration

Trilateration

Received Signal Strength(RSS)


Location Determination :


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Location Determination :

Triangulation


If distance AB, angles at A and B are known

then X and Y can be determined using basic

trigonometry

Sin A = Y / a

Sin B = Y / b

Y = a * Sin A = b * Sin B

Cos A = X / aX = a * Cos A = ABb * Cos B

O

A B

Yab

X


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Location determination: TDOA

Time Difference of Arrival(TDOA), Multilateration TOA measurement of time signal sent vs. time received:

distance d = time t * signal propagation speed s.

N.B. Assumes accurate clock synchronisation, sender knows time

of transmission

TDOAor measurement at 2 or more receivers (or sent from

2 or more senders)

use to estimate the difference in distances between the 2.



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Location Determination: Trilateration

Trilateration: uses absolute measurements of time-of-arrival from three or more sites

Trilateration is a method of determining the relativepositions of objects using the geometry of triangles in asimilar fashion as triangulation.


L ti d t i ti T il t ti


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Location determination: Trilateration


3 Equations to determine location of point O

w.r.t. known locations A,B, and C on a 2D plane

RA2 = X2+Y2

RB2 = (X-(AO+OB))2+Y2

RC2 = (X-AO)2+(Y-OC)2

Use substitution to get X and Y

X = (RA2- RB

2 + (AO+OB)2) / 2 (AO+OB)

Y = (RA2- RC2 +AO2+OC2) / 2OC)AOX / OC

OA

C

B

RC

RBRA

X

Y


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Location Determination: RSS

Received Signal Strength(RSS)Estimate the RF signal strength at a receiver

Knowing the transmission signal strength

Knowing the attenuation of the signal as a function of

distance and signal transmission strength, e.g., 1/r2



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Location Determination: Range

IR / BlueTooth: ?

RFID systems: ?

WLAN: ?

GPS: ?

GSM: ?



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Location Determination: Uncertainty

Distance & timing measurements has some uncertainty inpractice:

variable attenuation (due to moisture in air etc),

multi-path effects,

reflections,

spot interference,

knowing the time of transmission accurately etc (see also Chapter 11)

How can we correct for this uncertainty? We can measure signal w.r.t to multiple transmitters to correct for

this variability



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Location Determination: Handling

Inaccuracy & Uncertainty

Handling the lack of accuracy, uncertainty in the location

Accuracy requirements for some applications can berelaxed

Could use orientation or a priori knowledge of geo-attributes to help determine the location, .

Can use hybrid systems or assisted systems that combinestrengths and minimise weaknesses of several systems.



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Location & Other Spatial Abstractions

Location coordinate in itself is often not so useful, it is too

low-level

It is the Spatial context for a location that is useful and

gives it the location meaning. E.g.,

Forward-tracking: relation of the current coordination to anend coordination / future goal e.g.,

Backward tracking: relation of current location coordination

to start coordination, to past routes, to past goals


G


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Location Awareness: Geographical

Information System (GIS) Need spatial services to determine the spatial context

This is a GIS service

A GIS service needs to do more answer spatial queries, italso needs to be:


L ti A G hi l


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Location Awareness: Geographical

Information System (GIS)A GIS system supports services to support:

Spatial context representations

Spatial context capture

Spatial annotation: bind context to geometric object or view

Coordinate transformation

Spatial data storage Spatial analysis including queries

Spatial data output & cartography



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Geospatial Information System (GIS)

A service, such as a Geospatial Information System (GIS)service, is needed to answer spatial queries

E.g., Is there a type of service X within 1 km of here?.

GIS services represent real world objects

such as roads, land use, elevation with digitised spatial data.



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GIS: What the Data Represents

Geospatial data consists of multiple parts: Geometrical object

e.g., point, line, polygon etc

Geo-attributes that form the spatial context

e.g., types of feature, and associated attributes, e.g

Annotations of geometrical object



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GIS: Data Representation

GIS represents real world objects (roads, land use,elevation) with digitised spatial data

Real world spatial objects can be discrete objects(house)

continuousfields (rain fall, elevation)

Digitised GIS data consists of two parts Geometrical objects Spatial context / Geo-attributes


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GIS: Geometric Data Capture

There are a variety of methods used to capture Geo-context

Digitizer e.g.,

Scanner e.g.,.

Direct entry of surveyed or sensed data E.g.,, Photo interpretation of aerial photographs.

E.g.,

Can configure relative location accuracy vs. absolute

accuracy & level of accuracy.



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GIS: Spatial Context Capture

Geocoding: derive location from spatial context

Reverse geocoding: derive spatial context from location



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GIS Data Capture: Processing

Geo Data after capture usually requires editing

Vector data must be made "topologically correct" before itcan be used for some advanced analysis. Projections

Adjacency

To remove errors E.g.,



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GIS data coordinate Transformation

100+ different coordinate systems exist for positions

Likely that measured location co-ordinates & geospatialobject coordinates in GIS will be different

-> Need transformations



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GIS Data Storage & Retrieval ';

Many DBs with spatial extensions use GIS data structuresthat are based on the Open GIS Consortium (OGC)Geographical Markup Language (GML) standards

Spatial databases are optimised?



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GIS: Spatial Queries

Example query, How far, as the crow flies, from QueenMary to Mile End Tube?

SELECT (orig.buildinglocdest. buildinglloc)*37.5 AS "Distance (kms)"

FROM buildingl orig, buildingl dest

WHERE orig. buildinglname = Queens Building'

AND dest.buildingname = MileEnd Tube Station

A spatial query involves determining which indexed region a spatial object of interest is in where a region

bounds a set of spatial objects

then locating a specific object within that selected region,

e.g., determining the distance from Queen Mary (Object D) to Mile-

End Tube station (Object A)



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GIS: Spatial Queries


A

B

C

D

E

XY

Spatial Adaptation GIS Data o tp t


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Spatial Adaptation: GIS Data output

& Cartography Some main uses of spatial-adaptation:

????

Cartography is the design and production of maps, orvisual representations of spatial data.

The vast majority of modern cartography is done with thehelp of computers, usually using a GIS. Most GIS softwaregives the user substantial control over the appearance ofthe data



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GIS Data Output & Cartography

Cartographic work serves two major functions: It produces maps and other graphics,

To allow the map to be annotated with symbols and text forthe information of interest,

Web Map Servers facilitate the exchange of generatedmaps information via Web Services,

e.g., ???



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Lecture Outline


Context Adaptation

Spatial-Awareness



Temporal awareness



Context awareness: Indoor Call


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Context awareness: Indoor Call

Routing For Mobile Users

Active Badge Location System of Want et al. begun in 1989 Location awareness users to route calls through to their

nearest fixed line phone indoors

Readers detect signals from wearable active badges


Mobile User (ICT) Context awareness:


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Mobile User (ICT) Context awareness:

WAN Call Routing For Mobile Users

Basic mobile phone location determination . Determine which mobile phone transmitter, its area of

operation (its cell), phone is nearest to.

Phone users registered in HLR

When users pass between areas, a cell notifies its VLR When a call is made by user B to user A, the call first

queries the VLR

If A not there, call is made to As HLR


Location Determination in A Mobile


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Phone Network


MSC

MSC

Core PacketSwitched

Network

HomeLocationRegister

HLR

Mobile

Switching

Center

VLR

VisitorLocationRegister

Base station / Cell

User Ahas moved

User B

Group of Cells

User A

User C

User B

calls User

A


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Lecture Outline


Context Adaptation

Spatial-Awareness



Temporal awareness



Content Adaptation for Mobile


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Terminals

Content adaptation to two main types of ICT are consideredhere:

Adaption to the terminal

Adaption to the network connecting the terminal




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p

Terminals

UI facilitates presenting and entering information for humanuse

Universal content access entails content access via a

proliferation of interactive devices with diverse capabilities.


UI C t t R t ti


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UI Context Representation

The UI context can be defined in a UI device profile. There are several different specifications for representing

the UI profile.


C t t Ad t ti


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Content Adaptation

Needed to adapt content for display Much content designed for decimetre sized screens:

But what if displayed on small displays? e..g, mobile phone

But what if displayed on large screens? e.g., projectors,

Need Content adaptation this involves: Transformation of the created content representation to a differentone used in the access device,

Adaptation of the (multimodal) interaction

Adaptation to use a particular device display convention

Adaptation of the content itself.

See also the range of UI techniques adapted for use in

small and large displays (Chapter 5)


Content Adaptation Net ork A are


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Content Adaptation: Network-Aware

A service that is aware of the characteristics of the physicalnetwork is called underlay-networkaware (Chapter 11)

Enhancements are needed to TCP/IP network design to

support more flexible context-aware QoS delivery.



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Lecture Outline


Context Adaptation



Temporal awareness Composite Context Awareness


Temporal Awareness: Time


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Temporal Awareness: Time

Time may be modelled as a period

Time may be modelled as an instant,

Time can be modelled as a linear sequence



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Time Awareness: Scheduling


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Task scheduling is simplest when

Simple scheduling can involve deriving a personalised

schedule that it a subset of another schedule known apriori,

e.g., .




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Simple job scheduling algorithm is to partial order n tasks in a graph and to search it to

find a path


0

1T2 2T2 3T2 4T2

Task 1

Working

Task 2: Break

to eat & drink

Known periods but

flexible execution &

deadline

Known

execution

time Known

deadline

Task 3

Traveling

4T

Task 4

Leisure

T1 2T1 3T1

T1 2T1 3T1

1T41T3 5T 6T 7T3T2T1T 1T1

5T2

1T2

1T3 2T3

2T41T4

1T11T

2

1T32T2

2T1


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Lecture Outline


Context Adaptation



Temporal awareness



Composite Context Awareness for


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Mobile Users

Mobility context awareness is a good example of compositecontext adaptation.

Spatial awareness is used to adapt activities with respect to

their locality.

Information retrieval from remote sources can bepersonalised to users preferences.

ICT context-awareness is useful for mobile users so that it

adapts remotely accessed content so that it fits better the

characteristics of mobile access devices and better fits the

bandwidth available in the local wireless access loop.



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Context Composition Example: CRUMPETProject System


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Project System


Persona interestsl

Users

Terminals

Service Providers

Terminal

profile

Network

Link description Service

capabilities

Userpreferences

User

position

Interaction

& Service

Facilitation

Mediator

GPS

e.g., maps, routes, sight and

restaurant recommendations

CRUMPET P j t S t


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CRUMPET Project System

CRUMPET, Creation of User-friendly Mobileservices PErsonalised for Tourism, EU FP5 Project

system is an example of a composite context

adaptation application.

In this system, tourism information services suchas maps, routes and sight recommendations can

be adapted to a spatial context that pertains to the

current location, the personal context of a service

uses, the network context and the terminal context,


The CRUMPE T System


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My IP address

and port are...

Ok, here are your nearby

points of interests.

Components:

Map of the world

Diagnostics information

Client status (Agent and network status)

Points of interests

Map components:

Map of thenearby world

Start/Edit tour

Status bar with

proactive bulb

Here is my

new location.

CRUMPET Multi-Agent System Architecture


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85

Ubiquitous computing: smart devices,

environments and interaction

End user

Services

User

agent

MediatorAgents

Service

agents

Service

agents

Network

agents

Client /Terminal

Agent

Context-aware

Middleware

NetworkNetwork

agents

Fixed Network Services

Access

Node

Mobile

Device

wireless

Web Browser

GPS

Contet AdaptationService Agent Location agent

User modeling agent

Composite Context Awareness:


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CRUMPET System

Particular ordering of context-aware adaptation follows.

Users access terminal profile of memory & display

capabilities is exchanged with system during session start

Localisation is for example used twice

Current position of a user can be used to constrain a user'srequest and to further filter the relevant information.

Unless the relevant location is specified explicitly, user gets

information relevant for his or her current spatial context.

users movements within region can indicate their interests. E.g., a user visits a number of old churches, then he or she is

probably interested in churches and perhaps also other historic

buildings in this town, like an old city hall.




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CRUMPET System Users generate a lot of potential events of interest as they move.

These can be exploited for user modelling & to detect & anticipate

relevant user interests.

Hence, the combined location and personal model context can be

used to such as get me a map of things of interest at a location.

This is an example of environment context composition in which onetype of context (location) may be used to determine another type of

context (personal preferences) based upon a user context policy.

Finally, the network profile based upon monitoring the performance

of the local mobile terminal to access node, the content, e.g., a

personalised, location-aware map is adapted to the terminal andnetwork profile respectively.

Ubiquitous computing: smart devices, environments and interaction87



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Note the context composition challenges (Revision from

Chapter 5 slide set a )

Handling heterogeneity of representation

Handling heterogeneity of meaning

Mediating and coordinating context aggregation Ordering the adaptation to individual contexts

Different weightings for combining contexts

Handling uncertainty in combining contexts



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CRUMPET System Screenshots


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y


CRUMPET System: Fat-client


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Dillo

CRUMPET Services

Fixed Network

Service Provider

Service Provider

Service Provider

Wireless Station

CCA

MA

UMA

SCA

MAPA

CA

DCA CASACA

GSA

TA

SA

Satellite

MA

WMTP - full control over wireless link

Agent processing -

complete control over GSM

triangulation, GPS and browser

Wireless Station

y

Architecture

This deployment architecture has a larger client-side

Footprint and is suitable for deploying in

high end PDAs and PCs


CRUMPET System: Thin-Client


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y

Architecture

This deployment architecture has a very small client-side footprint and is

suitable for deploying in low end PDAs and suitably equipped mobile 'phones

Fixed Network

HTTP

Service Provider

Service Provider

Service Provider

Wireless Station

CCA

MA

UMA

SCA

MAPA

CA

DCA CASA

GSA

TA

SA

Satellite

HTTP - no control over link

JAVA process -

very little control

over GPS and browser

ExplorerCE

CRUMPET Services

Wireless Station


Lecture Outline


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Lecture Outline


Context Adaptation



Temporal awareness



Revision


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Revision

For each chapter

See book web-site for chapter summaries, references,

resources etc.

Identify new terms & concepts

Apply new terms and concepts: define, use in old andnew situations & problems

Debate problems, challenges and solutions

See Chapter exercises on web-site


Exercises: Define New Concepts


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p

Context-awareness


Exercise: Applying New Concepts


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