L14 Contex Aware Computing

8/12/2019 L14 Contex Aware Computing

1/39

BITSPilaniHyderabad Campus

Pervasive ComputingContext Aware Systems


2/39

BITS Pilani, Hyderabad CampusContent partially based on Resources Stefen Poslad kcs murti

Introduction

Modelling Context Aware Systems Mobility Awareness

Spatial Awareness

Temporal Awareness

ICT System Awareness

Overview

2
http://www.eecs.qmul.ac.uk/~stefan/ubicom/resources-instructors.htmhttp://www.eecs.qmul.ac.uk/~stefan/ubicom/resources-instructors.htmhttp://www.eecs.qmul.ac.uk/~stefan/ubicom/resources-instructors.htmhttp://www.eecs.qmul.ac.uk/~stefan/ubicom/resources-instructors.htmhttp://www.eecs.qmul.ac.uk/~stefan/ubicom/resources-instructors.htm


3/39


Context aware systems are systems that are aware of their

situation. in their physical, virtual (ICT)& user environment.

Can adapt the system benefiting from knowledge of that

situation.

Introduction


4/39


A context represents the state or situation in the

environment of a system that affects that systemsbehaviour

Context is any information that can be used to

characterize the situation

There are several dimensions or properties tocharacterise context.

There are many definitions of how to make systems

aware of changes in their context: context awareness

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

key property of smart environments.

Context

4


5/39


Collision detection

Spatial awareness Temporal awareness

Personalised systems.

Context presentation

Context tagging

Context filtering

Context based task activation

CA applications


6/39


Context types

6

Smart (Physical) Environments

Physical

Environment

Devices Context-aware

Physical

Environment

Context Types

CPI

Structure

Human ICT

Location-

aware

GIS

Location

Sensor

or 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


7/39BITS Pilani, Hyderabad CampusContent partially based on Resources Stefen Poslad kcs murti

Environment

What:

Type of physical environment awareness of temperature, light intensity, chemical etcWhere:

Spatial awareness or location awareness

When:

Temporal awareness

ICT Environment

How:

ICT awareness: awareness of how any context is created and adapted over an ICT

infrastructure.

User Environment

Who:

User context awareness, Personal Preferences, personal identity context,

User Activity or Task Context

Social (User) Context

Goal context

Why:

User or application goal

Context Adaptation:

Classification of Context


8/39



Simplest type of context-aware systemUses 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

Use of Current Context vs. use of Context History

9



Context determination: acquisition, accuracy particularly

of user context can be complex Active versus passive context acquisition

Single shot (static) versus dynamic acquisition

Heterogeneous context representation (syntax) and

semantics, interoperability Context distribution: Local context producer but remote

context consumer

CA Design issues: Context Determination

10



User Contexts may be incorrectly, incompletely, imprecisely

determined or predicted, ambiguous

Environment Contexts may be incorrectly, incompletely, imprecisely

defined, determined or predicted.

Contexts may exhibit a range of spatial-temporal characteristics

Contexts may have alternative representations

Contexts may be distributed and partitioned, composed of multipleparts that are highly interrelated

Contexts may generate data huge volumes

Context sources and local processes often need to embedded in a

low resource infrastructure

Context use can reduce the privacy of humans

Awareness of context shifts can distract users

CA: Challenges

11



Combine several low-level sensor inputs to better infer

user context,

Can Query user profile or model: abstraction that

characterises the user, preferences the user expresses,

Ask users to define their own context.

Observing user interaction

User Context Determination

12



Static environment contextdescribes aspects of a pervasive system that are invariant, such as a persons date

of birth

Dynamic environment context:

refers to a user or an environment context. These contexts can be highly variableover space and time, e.g., temperature.

Static versus Dynamic CA

13



New contexts can be created from sensors.

user contexts derived from simple contexts by Combining several simpler contexts

Combining homogeneous contexts

Combining heterogeneous contexts

Deriving high level context from lower level ones

Deriving a lower level context from a higher level one

Context Creation and Context Composition



Capture Physical Context

Capture User Context Context Processing

Adapt to Context

Manage contexts

CA: Life-cycle

15



General architecture for CA systems

16

Configuration

Actuators

Sensors

Environment

Abstraction

Display

User Tasks

Events

User

Context

ContextStore

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 Context

Creation

ContextControl

Access

Context Filter

Policies

Context

Discovery

Discovery
http://www.eecs.qmul.ac.uk/~stefan/ubicom/resources-instructors.htmhttp://www.eecs.qmul.ac.uk/~stefan/ubicom/resources-instructors.htmhttp://www.eecs.qmul.ac.uk/~stefan/ubicom/resources-instructors.htmhttp://www.eecs.qmul.ac.uk/~stefan/ubicom/resources-instructors.htmhttp://www.eecs.qmul.ac.uk/~stefan/ubicom/resources-instructors.htmhttp://www.eecs.qmul.ac.uk/~stefan/ubicom/resources-instructors.htm



Acquisition of user context: this can be derived from

users application tasks

Policy creation: created from users tasks to determine

how a 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.

User Context Creation

17



Acquisition of user contexts

such as human user identity, stereotypes and personal preferences

can be acquired directly or indirectly from user interaction.

Encapsulation and abstraction

enable the context to be accessed via a published interface;harmonize heterogeneous context values into a common

representation;

convert between different representations and structures for the

same type of context.

Filtering: consider events within a certain range that adhere to defined

context constraints or policies.

Environment Context Creation / Capture

18



Context composition:

An application may govern the use of multiple environment

contexts Mediation:

multiple environment contexts are linked and interrelated.

Adaptation:

passive or active or control:

Passive (or Presentation): environment context is used asa constraint to select or query information from anapplication or user context

Active (or Automatic): The application or user contextadaptation automatically adapts to the environment

context. Control: the user context may be used to control the

environment.

Context Processing

19



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

Context Composition: Motivation

20



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

Context Composition: Challenges

21



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 and users

Determination of a proposed joint context for meeting can becomplex

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,

Context Composition, Heterogeneous Contexts & Interoperability

22


23/39


Discovery:

Directory services enable context sources, stores and users to

be registered and discovered.

Storage:

of context data into some data resource

may include history based organization of the stored context

Sharing of environment and goal contexts

Access control:

protects the privacy of any context information

.

Context Management

23


24/39


Passive context adaptation system Context is presented to users

Context-based tagging

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

Context Adaptation: Passive vs Active

24


25/39


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

Context Adaptation Benefits

25


26/39


User Contexts may be incorrectly, incompletely,determined or ambiguous

Environment Contexts may be incorrectly incompletely,determined or ambiguous

Contexts may exhibit a range of spatial temporalcharacteristics

Contexts may have alternative representations Contexts may be distributed and partitioned, composed

of multiple parts that are highly interrelated.

context awareness may generate huge volumes of data

may need to be embedded in low resourceinfrastructures

Context use can reduce the privacy of humans

Challenges in modelling contexts


27/39


The UI context can be defined in a UI device profile.

There are several different specifications forrepresenting the UI profile.

UI Context Representation

27


28/39


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 different one used in

the access device, Adaptation of the (multimodal) interaction

Adaptation to use a particular device display convention

Adaptation of the content itself.

Content Adaptation

28


29/39


A service that is aware of the characteristics of the

physical network is called underlay-networkaware

Enhancements are needed to TCP/IP network design to

support more flexible context-aware QoS delivery.

Content Adaptation: Network-Aware

29


30/39


Mobility context awareness is a good example of

composite context adaptation. Spatial awareness is used to adapt activities with respect

to their locality.

Information retrieval from remote sources can be

personalised 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.

Composite CA for Mobile Users

30


31/39


Navigation

Automatic annotation of local recordings in the field

Filtered content for mobile users

Composite CA for Mobile Users: Applications

31


32/39


Context Composition Example: CRUMPET Project System

32

Persona interestsl

Users Terminals

Service Providers

Terminal

profile

Network

Link description Service

capabilities

Userpreferences

Userposition

Interaction

& Service

Facilitation

Mediator

GPS

e.g., maps, routes, sight and

restaurant recommendations

CRUMPET P j t S t


33/39


CRUMPET, Creation of User-friendly Mobile

services PErsonalised for Tourism, a compositecontext adaptation application.

In this system, tourism information services

such as 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,

CRUMPET Project System

33

Th CRUMPE T S t


34/39


The CRUMPE T System

34

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 the

nearby world

Start/Edit tour

Status bar with

proactive bulb

Here is my

new location.

CRUMPET M lti A t S t A hit t


35/39

BITS Pilani, Hyderabad CampusContent partially based on Resources Stefen Poslad kcs murti`

CRUMPET Multi-Agent System Architecture

35

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

C it C t t A h ll


36/39


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

Composite Context Awareness- challenges:

36

CRUMPET S t F t li t A hit t


37/39


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

CRUMPET System: Fat-client Architecture

37

CRUMPET S t Thi Cli t A hit t


38/39


CRUMPET System: Thin-Client Architecture

38

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
http://www.eecs.qmul.ac.uk/~stefan/ubicom/resources-instructors.htmhttp://www.eecs.qmul.ac.uk/~stefan/ubicom/resources-instructors.htmhttp://www.eecs.qmul.ac.uk/~stefan/ubicom/resources-instructors.htmhttp://www.eecs.qmul.ac.uk/~stefan/ubicom/resources-instructors.htmhttp://www.eecs.qmul.ac.uk/~stefan/ubicom/resources-instructors.htmhttp://www.eecs.qmul.ac.uk/~stefan/ubicom/resources-instructors.htm


39/39

Date post:	03-Jun-2018
Category:	Documents
Upload:	anupam20099
View:	251 times
Download:	0 times

L14 Contex Aware Computing

Documents