Context-Aware Computing
Overview and Case Studies
Marko Jurmu
MediaTeam Oulu Group
University of Oulu
Finland
March 13th, 2007
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Outline:
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Fact Sheet: Finland
Motivation
Definitions of Context
Effects of Context-Awareness
Example Application Domains
CASE 1: Connectivity Management
CASE 2: RFID Symbolic Tags
CASE 3: Wearable Sensors
Raised Issues
References
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Fact Sheet: Suomi (Finland)
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Population: 5.3 mi
Area: 330.000 km2 (127.000 sq mi)
Independent since: Dec. 6, 1917
Capital: Helsinki (ca. 1 mi)
• Home of:
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Santa Claus
NOKIA
Linus Torvalds
Jari Litmanen
Teemu Selänne
Jari Kurri
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Motivation
• Traditional computer systems execute blindly
– Pre-defined application logic
– Static user interfaces that require explicit attention
• New kind of computing
– Mobility is becoming a norm
– Applications execute in less static
environments
• What can be done?
– Enable computer systems to sense their surroundings
– Encode changes in the surroundings to reflect to the application
behavior
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Motivation cont’d
• But:
– Coding explicit reflections into applications is laborous
– Applications do not necessarily understand all changes
– Applications may not be able to collect all the necessary information
• We need:
– Supporting platforms that facilitate application execution
– Ways to gather disparate information and provide it in a unified way
– Mechanisms to provide information without loss in semantics
• These are the main research problems of context-aware
computing
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Definitions of Context
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Schmidt et al. [1]:
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Context is a series of transient hierarchical feature spaces
Very systematic definition
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Definitions cont’d
• Dey [2]:
– ”Context is any information that can be used to characterize the
situation of an entity. An entity is a person, place, or object that is
considered relevant to the interaction between a user and an
application, including the user and the application themselves.”
– Very loose definition, reflects well the common paradox in contextaware computing:
• Applications can never be made aware of all possible context
• In practice, the subset of context utilized by applications is strongly
dictated by the sensing capabilities of underlying computer system
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Definitions cont’d
• Dey’s definition of context-awareness [2]:
– ”A system is context-aware, if it uses context to provide relevant
information and/or services to the user, where relevancy depends on
the user’s task”
– Important contrast: Previous discussion was strongly related to
providing information that enables dynamic changes in the execution
of the application
• According to this definition, application is also context-aware if it can use
context to filter the information presented to the user
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Levels of Context
• In their work [1], Schmidt et al. define 4 levels of context:
– Raw sensor data
• Readings acquired from
individual sensors
– Cues
• Abstracted sensor data,
possibly temporally aggregated
– Context
• Description of the current situation
on an abstract level
– Scripting
• Allowing applications to benefit
from context through simple
scripts
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Effects to Application Logic
• Context-aware applications need to be designed differently
from static applications:
– Agile behavior on the face of rapid changes
– Platform independence is required
– Logic is distributed to better reflect the variance in the computing
environments
• The reflection to context changes can be encoded in several
ways:
– Definition of explicit rules and conditions
– Increasing / decreasing application functionality
– Dynamically maintaining the FSMs that control
the application
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Effects to Interaction
• Traditional interaction:
– Based on explicit user input
– Static UIs with a certain conceptual models
– User overwhelmed with unnecessary information
• Situations worsens with ever-increasing information
• Context-aware interaction:
– Based on combination of implicit and explicit I/O
• Implicit interaction does not require additional cognitive load
– UIs that filter information and lessen the explicit controlling
– More intuitive interaction models for users can be enabled
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Example Application Domains
• Location-aware applications:
– Map-based guidance
– Focused advertising
– Weather / traffic services
• Network-aware applications:
– Video streaming
– VoIP
– File management operations
• Combinations of these and other contexts:
– Basically the list is endless, the following presents 3 enablers
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CASE 1: Connectivity Management
• Background:
– Currently, wireless networking appears
through heterogeneous overlapping
access networks
– Mobility of the users is causing constant
changes to the configuration of active
radio interfaces
– Connectivity can be based on
infrastructural or ad-hoc links
– Networking applications in the mobile
device need coherent mechanisms to
cope with networking conditions
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CASE 1 cont’d
• Solution [3]:
– Introduce a persistent networking interface for applications
– Applications only see channels, and can specify different policies
for network utilization
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CASE 2: RFID Symbolic Tags
• Background:
– Invoking specific actions from mobile
phone requires the navigation of
hierarchical menus
– Can be very time-consuming, and
does not guarantee that all
action-related parameters are
entered correctly
– All in all: Highly explicit UI
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CASE 2 cont’d
• Solution [4]:
– Add RFID tags with intuitive symbols to the environment
– Tag has action-related parameters encoded, so menu-based setting
is not required
– Still, users only see symbolic actions that can be invoked by touch
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CASE 3: Wearable Sensors
• Background:
– Computer systems need information regarding the activities of the
user to be able to support them
– Having basic context like location is not necessarily enough
– Activity is also correlated with artifacts being currently utilized
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CASE 3 cont’d
• Solution [5]:
– Equip users with wearable sensors
– Additional sensors in artifacts
give information on usage
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Raised Issues
• User control
– Context-awareness takes control away from users
– What is the right amount of user control?
• User must feel that he/she is in control of the system
– Two extremes:
• Application asks everything from user (not very feasible)
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(certainly not very feasible)
• Privacy
– Context-awareness requires the acquisition and storaging of
information related to users and their surroundings
– How to ensure correct management and avoid leakages?
– How to avoid the collection of sensitive information?
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Future Trends
• From application point-of-view, mobility is turning
multidimensional
– Over administrative domain boundaries
– Over device boundaries
– Over social boundaries
• Living environments are increasingly saturated with
intelligent electronics
– Available services increase
– Digital and physical worlds increasingly overlap
• Challenges lie ahead especially in dynamic session
management between environments and mobile users
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References
[1]
Schmidt, A., Beigl, M. & Gellersen, H.-W. (1999), There is more to context than location,
Elsevier Computer and Graphics Journal 23(6): 893-901.
[2]
Dey, A. (2000), Towards better understanding of context and context-awareness, CHI
2000 Workshop on the What, Who, Where, When, Why and How of Context-Awareness.
[3]
Sun, J., Riekki, J., Jurmu, M. & Sauvola, J. (2005), Adaptive connectivity management
middleware for heterogeneous wireless networks, IEEE Wireless Communications 12(6):
18-25.
[4]
Riekki, J., Salminen, T. & Alakärppä, I. (2006), Requesting pervasive services by touching
RFID tags, IEEE Pervasive Computing 5(1): 40-46.
[5]
Pirttikangas, S., Fujinami, K. & Nakajima, T. (2006), Feature selection and Activity
Recognition from Wearable Sensors, Proc. International Symposium on Ubiquitous
Computing Systems (UCS2006), Seoul, Korea, Oct. 11-13, 2006, pp. 516-527.
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Contact:
marko.jurmu@ee.oulu.fi
www.mediateam.oulu.fi
www.oulu.fi
http://en.wikipedia.org/wiki/Finland
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