The Design and Applications of a Context Service Mobile Computing and Communication Review, Vol'6 No

1
The Design and Applications of a Context Service
Mobile Computing and Communication Review, Vol.6
No. 1(H. Lei et al IBM TJ Watson Lab.)

• 2004. 1. 12
• Kyung-Lang Park

2
Contents

• Introduction
• Context service
• Design considerations
• Architecture
• Applications of context
• Related work
• Conclusion

3
Introduction

• Context awareness enhances existing/new
  applications
• Adapt themselves to better suit the needs
• To make context information
• Need for context collection and dissemination
• We develop a Context Service as an integral part
  of the pervasive computing
• Applications can interact with the context
  service to obtain the information without
  difficulty of the management

4
Def. of context service

• Def. of context
• Any information that can be used to characterize
  the situation of an entity
• Classification of context
• Transient context (a single point)
• Persistent context (recurrent pattern)
• Def. of context service
• Collects and maintains context information

5
Some definitions

• Subject
• Entities related to contexts. It can be users or
  objects (e.g., equipment or packages)
• Context source
• Third parties that collect and provide
  information
• Clients
• Request context information about one or more
  subjects
• Controller
• Control the context information

6
Design considerations

• Privacy
• User should maintain control of context
• Prioritize the privacy policy of subjects
• Quality of Information
• Context sources should express inaccuracies and
  uncertainty, via QoI metrics
• Freshness, confidence, error and so on
• Pass along QoI data from sources to client
• Extensibility
• Support new and unanticipated source of context
  information
• Support diverse applications

7
Architecture overview
8
Programming model

• A client partially fills out a form (QoI)
• The context service responds with the form data
• A context source may push new or updated context
  information
• Application can obtain heterogeneous context with
  standard APIs

9
Context drivers

• Its a plug-in component
• Consists of
• Context Driver Interface
• Uniform abstraction for context drivers
• Internal utilities
• Context cache
• Work pacer
• Event engine
• Privacy engine
• A context driver may interact with several
  context sources
• A context service can be a source
• Both use push and pull technologies
• Examples
• IM context driver
• calendar driver
• Location
• desktop

10
Privacy model

• Specify policies for organizations
• RBAC (Role Based Access Control)

11
Applications of context

• Notification Dispatcher

12
Applications of context

• Pervasive Content Distribution

13
Relate work

• Schilit et al
• Application customization system
• Spreitzer and Theimer
• Disseminating location information
• Hull
• Context service
• Georgia Techs Context Toolkit
• Cricket Location-Support System
• iValet

14
Conclusion

• described a middleware infrastructure that
  enables the collection of context
• Privacy
• Quality of information
• Extensibility