chair for communication technology (comtec), faculty of electrical engineering / computer science...

Chair for Communication Technology (ComTec), Faculty of Electrical Engineering / Computer ScienceChair for Communication Technology (ComTec), Faculty of Electrical Engineering / Computer Science

Prediction of Context Time Series

Stephan Sigg, Sandra Haseloff, Klaus David

University of Kassel, Germany

WAWC’07, August 16, 2007Lappeenranta, Finland

© © ComTec ComTec 20072007

Dr. Sandra HaseloffDr. Sandra Haseloff22

Contents

• Introduction to Context Prediction

• Context Abstraction Levels

• Context Prediction Architecture

• Context Prediction Algorithm

• Simulation Results

• Conclusion



Context Awareness Introduction – Abstraction Levels – Architecture – Algorithm – Simulation – Conclusion

• In current systems, mostly present and/or past context considered

• Adaptation to anticipated future contexts➜ Context Prediction

Definition by [Dey]:

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.



Context Prediction Introduction – Abstraction Levels – Architecture – Algorithm – Simulation – Conclusion

What is Context prediction?

Given:

Time series of observed contexts

Task:

Infer information about future contexts



Context Prediction (2) Introduction – Abstraction Levels – Architecture – Algorithm – Simulation – Conclusion



Context Prediction – Definition Introduction – Abstraction Levels – Architecture – Algorithm – Simulation – Conclusion

• Let T be a context time series

• Given a probabilistic process p(t) that describes the behaviour of the user in time

• Context prediction is to learn and apply a prediction function

that approximates p(t)

miiiki tttti TTtf

,, 1:)(



High-Level and Low-Level Context Introduction – Abstraction Levels – Architecture – Algorithm – Simulation – Conclusion



High-Level and Low-Level Context (2) Introduction – Abstraction Levels – Architecture – Algorithm – Simulation – Conclusion




• Should prediction be based on high-level contexts or on low-level contexts?

• Context prediction in the literature is based on high-level contexts

• Prediction based on low-level contexts is beneficial in some cases

• No architectures for low-level context prediction available



Context Prediction Architecture Introduction – Abstraction Levels – Architecture – Algorithm – Simulation – Conclusion

Integrated into FOXTROT (Framework for Context-Aware Computing) based on FAME2 middleware



Context Prediction Architecture (2) Introduction – Abstraction Levels – Architecture – Algorithm – Simulation – Conclusion



Context Prediction Architecture (3) Introduction – Abstraction Levels – Architecture – Algorithm – Simulation – Conclusion

• Context HistoryObserved past contexts

• RulebaseTypical context patterns

• Learning ComponentCreation and update of rulebase

• Prediction ComponentActual context predictionUsage of alignment algorithm



Context Prediction Algorithm Introduction – Abstraction Levels – Architecture – Algorithm – Simulation – Conclusion

Alignment algorithm inspired from bioinformatics



Context Prediction Algorithm (2) Introduction – Abstraction Levels – Architecture – Algorithm – Simulation – Conclusion



Simulation Results Introduction – Abstraction Levels – Architecture – Algorithm – Simulation – Conclusion

• Simulations on synthetic and concrete data have been performed that confirm the results

• Simulations conducted so far:– Several simulations on synthetic data

– Prediction of windpower

– Prediction of GPS trajectories

• Comparison of prediction accuracy for high-level vs. low-level prediction and for different prediction algorithms



Simulation Results (2) Introduction – Abstraction Levels – Architecture – Algorithm – Simulation – Conclusion

• Windpower prediction results– ARMA algorithm best suited

– Alignment algorithms performs well

– Reasons: Periodic patterns in numerical data, small prediction horizon

• Location prediction results– Alignment algorithm best suited

– Reasons: Typical behaviour patterns, longer prediction horizon, high sampling intervals



Conclusion Introduction – Abstraction Levels – Architecture – Algorithm – Simulation – Conclusion

• Context prediction is a promising extension for context-aware applications

• Context prediction based on low-level contexts can have benefits to prediction based on high-level contexts

• Architecture for context prediction based on low-level contexts

• Novel, powerful algorithm for context prediction

chair for communication technology (comtec), faculty of electrical engineering / computer science...

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