Context-Awareness on Mobile Devices - the Hydrogen Approach
Thomas Hofer, Wieland Schwinger, Mario Pichler, Gerhard Leonhartsberger, Josef Altmann
(Software Competence Center, Hagenberg, Austria)
Werner Retschitzegger
(Johannes Kepler University, Linz, Austria)
36th Annual Hawaii International Conference on System Sciences (2003)
2008. 10. 13.
Summarized & presented by Babar Tareen, IDS Lab., Seoul National University
Copyright 2008 by CEBT
Introduction
Mobile devices lack resources
Computing power
Memory
Power Supply / Battery Life
Not permanently connected to a network
But mobile devices are
Much more personal (One device for one user)
Move with their users (User ‘s location is that of the device)
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Copyright 2008 by CEBT
Related Work
Context Toolkit
Context can come from many distributed machines
Widgets read sensors
Dynamic detection of remote sensors in not supported
GeoNotes
Users can create notes and stick those to geographic locations
Considers location context only
CampusSpace
exploits the signal strength of roaming client devices registered at WLAN access points
Nord et al.
Reading the location information with peer-to-peer position sharing
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Copyright 2008 by CEBT
Req. for C.A. Framework on Mobile Devices
Lightweightness
Consider limited processing power
Extensibility
Support connections to remote sensors
Robustness
Has to be robust against disconnections of remote sensors
Meta-Information– Distance of the device to the sensor
– Preciseness of the sensor
– And more…
Context-Sharing
Mechanism to share sensed context with other devices
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Copyright 2008 by CEBT
Hydrogen Context-Framework
Three layered architecture
Application Layer
Management Layer
– Context server stores all context data
– Context server can share context data with other devices
– Provides methods to access context
– Context can be pulled or pushed
Adaptor Layer
– Gets information from sensors
– Abstracts sensed data
– Solves problem of simultaneous access
All three layers reside on one device
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Copyright 2008 by CEBT
Benefits of the Framework
No network disconnections
Applications communicates only with local context server
Drops historical context data management
Context sharing on peer-to-peer basis
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Copyright 2008 by CEBT
Implementation
Prototype implemented in
Platform: PersonalJava (Jeode VM, J2ME J9)
Device: iPAQs (3660 and 3870)
OS: MS PocketPC 2002
Processor: 206 MHz
Resolution: 240 x 320
RAM: 64MB
IR Port: 115 Kbps
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iPAQ 3660
iPAQ 3870
Copyright 2008 by CEBT
Implementation
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Copyright 2008 by CEBT
Context
Supported types
Time
Location
Device
User
Network
Other context types can be added
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Copyright 2008 by CEBT
Other Components
Context Server
Java Executable
Accessible through a port
Communication possible via XML and Java objects
Adaptors and Applications
ContextClient deals with all communication issues
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Copyright 2008 by CEBT
Exemplary Application
Context-aware Postbox
Sends and receives multimedia data
– Images
– Text
– Business cards
Adopts images according to device capabilities
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Copyright 2008 by CEBT
Future Work
Using XML Schema for validation
Context Sharing
Sharing available information between devices
Security and Reliability
User’s control over context sharing
Handling contradictory information
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Copyright 2008 by CEBT
About the Paper
Good, Why ?
Looked into previous available frameworks and come up with a new design
Very simple framework design suggested
Bad, Why ?
Details about sharing context are missing (Authors have highlighted that sharing context is an open issue)
Prototype application not good enough to demonstrate usefulness of the framework
When application was about to receive the data, user should have been asked if he needs Good quality or Avg. quality image
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Copyright 2008 by CEBT
Discussion
Context Server
acts as a repository
it just stores the data
does not care about the context type
Authentication between framework components
Poor architecture from security perspective
What if I replace the Context Server with my own code which acts like normal context server but sends all context data to a 3rd person??
NOTE (Good or Bad ??): No Ontologies used
No reasoning engines used
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