a survey on context-aware computing center for e-business technology seoul national university...

A Survey on Context-Aware Computing

Center for E-Business TechnologySeoul National University

Seoul, Korea

이상근 , 이동주 , 강승석 , Babar Tareen

Intelligent Database Systems LabSchool of Computer Science & EngineeringSeoul National University, Seoul, Korea

Copyright 2008 by CEBT

Introduction

We gathered papers below and categorized into 4 groups– Survey Papers (8)

– Context Models (7)

– Domain Dependent Applications (3)

– Architectural Approaches (17)

Survey on Survey Papers

A Survey on Context-aware Systems (2007)

Middleware for Distributed Context-Aware System (2005)

Is Context-Aware Computing Taking Control Away from the User?-Three Levels of Interactivity Examined (2003)

Towards a Better Understanding of Context and Context-Awareness (2000)

A Survey of Context-Aware Mobile Computing Research (2000)

Context-Aware Computing Applications (1994)

Semantic Tech & Context - 2


History of Context-Aware Com-puting

Active Badge Location System (Wang et al., 1992)

Term ‘Context-aware’ appeared in Schilit and Theimer(1994)

Authors describe context as location, identities of nearby people, objects, and changes to those objects

Couple of location-aware tour guides

Abowd et al., 1997; Sumi et al., 1998; Cheverst et al.,2000

Providing information according to the user’s current location

Ryan et al. (1997) referred to context as the user’s location, environ-ment, identity, time

Day (1998) : the user’s emotional state, focus on attention, location, and orientation, date and time, as well as objects and people in the environ-ment

Dey and Abowd (2000)

Any information that can be used to characterize the situation of entities that are considered relevant to the interaction between a user and an application, including the user and the application themselves



Three Levels of Interactivity

Personalization

Common feature of computing applications

Increased level of tailoring in software

The majority of users use the default setting of change a small subset of the pos-sible features

Active and Passive Context-awareness

Using Chen and Kotz’s definition of context-awareness

Active Context-awareness

– Changing the content autonomously on the basis of measured sensor data

– Ex) Mobile phone that changes its time autonomously by new time zone

Passive Context-awareness

– Presenting the updated context to the user

– Let the user specify how the application should change

– Ex) mobile phone prompts the user with information about the time zone change


History of Context-Aware Com-puting

Burnett (2003) and Gustavsen (2002)

External and internal

Hofer et al. (2002)

Physical and logical

Dey and Abowd, 2001

Entities: Places, People, things

Attributes: identity, location, status, time, …


Context that can be measured by hardware sensors, i.e,., locationa, light, sound, movement, touch, temperature or air pressure

Context that can be captured by user interactions, i.e., the user’s goals, tasks, work context, emotional state

Easier to sense


Categories of Context Aware Applica-tions

Proximate Selection

A user interface technique where the located-objects that are nearby are emphasized or otherwise made easier to choose

Automatic Contextual Reconfigurations

Reconfiguration is the process of adding new components, removing existing components or altering the connections between components

Contextual Information and Commands

Queries on contextual information can produce different results according to the context in which they are issued

Context-Triggered Actions

Context-triggered actions are simple IF-THEN rules used to specify how context-aware systems should adapt

6


Design Principles - Architecture

Chen (2004) presents three different approaches on how to acquire contex-tual information

Direct sensor access – devices with sensors locally built in

Middleware infrastructure – hiding low-level sensing details, more extensible

Context Server – multiple clients ac-cess to remote data source

Winograd (2001)

Widgets – a software component that provides a public interface for a hard-ware sensor, hiding low-level details of sensing, managed by widget manager

Networked services – more flexible, discovery techniques are used, not as efficient as a widget architecture but provides robustness

Blackboard model – data centric view, simplicity of adding new context sources (easy configuration)


Layered conceptual framework for context-aware systems

Physical Sensors – hardware sensorsVirtual Sensors – context data fro apps or servicesLogical Sensors – combine physical & virtual sensors with addi-tional information from DBs or other sources


Design Principles – Context Mod-els

Models

Key-Value models

Markup scheme models

– Use a hierarchical data structure consisting of markup tags

Graphical models

– Use UML to represent context information

Object oriented models

Logic based models

Ontology based models

Attributes

Context type

Context value

Time stamp

Source

Confidence

8

Simplicity

Flexibility

Genericity

Expressiveness

Requirements


Existent systems and frameworks

Three types of existing context-aware systems

Location-aware systems

Context-aware systems

Context-aware frameworks

– Context Managing Framework (2003)

– SOCAM (2004)

– CASS (2004)

– CoBrA(2003)

– Context Toolkit (2000)

– Hydrogen project (2002)

– CORTEX (2004)

– Gaia (2002)

– …


Architecture

Resource discovery

Sensing

Context model

Context processing

Historical context data

Security and privacy


Existent systems and frameworks


More Criteria & Conclusion

The direct comparison of the named systems and frame-works shows their similarity concerning the layered struc-ture

Mainly use physical sensors only

Lack of security and privacy modules

Standardization is required

Scalability issues


Survey Schedule

Paper Selection(1 week)

Survey (4 weeks)

CASS, Hydrogen

Gaia, SOCAM

Context Toolkit, CORTEX

Context Fusion Networks, The Context Fabric

Other Architectures

Context-Aware Computing Conceptual Framework (1~2 weeks)

Generalize technology components

Technology Map about Context-Aware Computing

Conceptual Framework

Technology Roadmap

Evaluation (2~3 weeks)

Scenario Set-up

Comparison Table

Evaluate each approach


a survey on context-aware computing center for e-business technology seoul national university...

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