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A Survey on Context-Aware Computing : Past, Present, and Future. Sang- keun Lee Intelligent Database Systems Lab School of Computer Science & Engineering Seoul National University, Seoul, Korea. Center for E -Business Technology Seoul National University Seoul, Korea. Motivation. - PowerPoint PPT Presentation
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A Survey on Context-Aware Computing: Past, Present, and Future
Center for E-Business TechnologySeoul National University
Seoul, Korea
Sang-keun Lee
Intelligent Database Systems LabSchool of Computer Science & EngineeringSeoul National University, Seoul, Korea
Copyright 2008 by CEBT
Motivation
Context-Aware System
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History of Context-Aware Computing :Context Definition
Term ‘Context-aware’ appeared in Schilit and Theimer(1994) Authors describe context as location, identities of nearby peo-
ple, objects, and changes to those objects Ryan et al. (1997) referred to context as the user’s location,
environment, 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 environment
Dey and Abowd (2000) Any information that can be used to characterize the situation
of entities that are considered relevant to the interaction be-tween a user and an application, including the user and the ap-plication themselves
Copyright 2008 by CEBT
History of Context-Aware Computing :Application & System, Context Model
Active Badge Location System (Wang et al., 1992) One of the first context-aware systems Forward phone calls to a telephone close to the user
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
Watson Project (Budzik and Hammond, 2000) W3C, RDF available (2000) IntelliZap (Finkelstein, 2001) Context Toolkit (Dey and Abowd, 2001)
p2p architecture + centralized discoverer, attribute-value tuple/XML - Context aggregation/interpretation, historical context data, Context Ownership (Privacy)
Hydrogen (Hofer, 2002) local/remote context, Object Oriented Model, process higher-level context
abstraction in application layer
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History of Context-Aware Computing :Application & System, Context Model
Gaia project (Roman’s) Extends operating system contepts to include context-awareness 4-ary predicates in DAML+OIL, context processing is based on first-order
logic operation Graphical Context Model: ORM (Hendricksen, 2003) Context Managing Framework (Koripaa, 2003)
Centralized server CoBrA- Context Broker Architecture (Chen, 2003)
COBRA-Ont(Ontology Model), Inference Engine, historical context data, Broker federation – Avoiding bottleneck Context Knowledge base – You can assert, delete, modify, query the stored
data(API) Flexibile policy language to control context access called Rei (privacy)
2004 W3C, OWL available
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History of Context-Aware Computing :Application & System, Context Model
Markup scheme model: Composite Capabilities/Preference Profile (CC/PP) (W3C, 2004)
SOCAM(Service-Oriented Context-Aware Middleware) (Gu, 2004) Upper ontology, Domain-specific Ontology
CASS (Fahy and Clarke, 2004) CORTEX (2004)
Based on sentient object model – sensor fusion to manage uncertainty of sensor data
Graphical Context Model: Context Modeling using UML (Sheng and Benatallah, 2004)
CoCA (Ejigu, 2007) Enhanced CoCA (Ejigu, 2008)
Using a hybrid context management model – Relational Database, Ontology Tools
Heuristics for better performance
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History of Context-Aware Computing:Sensor Definition
Burnett (2003) and Gustavsen (2002) External and internal
Hofer et al. (2002) Physical and logical
Semantic Tech & Context - 7
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
Copyright 2008 by CEBT Practical Semantic Technology - 8
Copyright 2008 by CEBT Practical Semantic Technology - 9
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The History in Summary Specific Context Definition to General Context Definition Non-Flexible Context Models to Flexible and Extensible
Context Model Domain-specific Applications to General Frameworks
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Categories of Context Aware Applica-tions Schilit (1994)
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
Sang-keun Lee Context-Aware / Personalized Contents Push Seamless Device Switching Automatic Device Configuration Decision Support/Suggestion Context Aware User Interface
11Context-aware computing applications (Schilit, B.; Adams, N.; Want, R.)Mobile Computing Systems and Applications, 1994. Proceedings., Workshop onVolume , Issue , 8-9 Dec 1994 Page(s):85 - 90
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An Example of Domain-dependent Applications: Cyberguide : A mobile context-aware tour guide (1997)
Goal know where tourist is, and what she is looking for predict and answer question she may pose provide interaction with other people and environment
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Design Principles – Architecture Chen (2004) presents three different approaches on how to acquire contextual in-
formation Direct sensor access – devices with sensors locally built in Middleware infrastructure – hiding low-level sensing details, more extensible Context Server – multiple clients access to remote data source
Winograd (2001) Widgets – a software component that provides a public interface for a hardware 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) Architecture Style
Peer to Peer– Limitation of Memory Resource, CPU Performance– Only uses local built-in sensors
Centralized Approach– Robustness
Baldauf, M., Dustdar, S., and Rosenberg, F. 2007. A survey on context-aware systems. Int. J. Ad Hoc Ubiquitous Comput. 2, 4 (Jun. 2007), 263-
277. DOI= http://dx.doi.org/10.1504/IJAHUC.2007.014070
Copyright 2008 by CEBT
Hydrogen (2002) Framework Architecture
Three layer– Application layer– Management layer
Providing and retrievingcontexts and sharingcontext informationwith other devices usingP2P communication
– Adaptor Layer Separating context storing, sensing from other layers Responsible to get information from sensors Providing same context information to multiple applications
All application have access to all context data by querying the Con-textServer
All layers are located on one device– Robust against network disconnections, Peer to Peer
Object-oriented Context Model
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SOCAM Architecture (2004) Context providers, Context interpreter, Context database, Context-aware services, and Service
locating service Architectural Requirements
A common context model that can be shared by all devices and services A set of services that perform context acquisition, context discovery, context interpretation and
context dissemination Upper/Domain-specific Ontology
Context Providers
• Acquire context from sources
Context Interpreter
• Provides logic reasoning
Context Database
• Stores context ontologies
Context-aware Services
• Adapt the way they behave
Service Locating Service
• provides a mechanism where Context Providers and the Context Interpreter can advertise their presence
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The Context Fabric (2004) Primarily concerned with pri-
vacy rather than with context sensing and processing
provides an architecture for pri-vacy-sensitive systems, as well as a set of privacy mechanisms that can be used by application developers
Previous work on privacy has tended to focus on anonymity or on keeping information from hackers
Confab’s focus is in empowering people with choice and informed consent, so that they can share the right information, with the right people and services, in the right situation
Copyright 2008 by CEBTIDS Lab. 17
The CoCA Service Platform (2007)
Interface Manager Manages a UI and interface between the CoCA platform and other modules
Data Source Responsible to provide necessary data to the core service (GCoM)
Core Service Responsible to provide the core context aware service after reasoning on the com-
ponents Supplementary Service
Knowledge discovery & Collaboration service
The Platform aims at acquiring and utilizing context information to provide appropriate services E.g) A cell phone is always set to
vibrating mode when its holder is in the libraryIt filters and sends use-
ful contexts to the con-text repository
It Keeps the rules in the rule repository
It consists of domain depen-dent/independent ontology
Reasoning -> Decision & ActionInterpretation, Aggregation
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The Enhanced CoCA Service Platform (2008)
Enhanced version of CoCA Combine the best of the relational approach and ontology approach Selective feature of loading only relevant context data into the rea-
soner using heuristics
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Summary: Existing systems and frameworks
Baldauf, M., Dustdar, S., and Rosenberg, F. 2007. A survey on context-aware systems. Int. J. Ad Hoc Ubiquitous Comput. 2, 4 (Jun. 2007), 263-
277. DOI= http://dx.doi.org/10.1504/IJAHUC.2007.014070
Copyright 2008 by CEBT
Criteria
Henricksen, K., Indulska, J., McFadden, T. and Balasubramaniam, S. (2005). Middleware for distributed context-aware systems. In: Robert
meersman and Zahir Tari et al International Symposium on Distributed Objects and Applications (DOA), Agia Napa, Cyprus, 31 October - 4 No-
vember, 2005.
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Discussion Does a context-aware system bother users?
MS Office Assistant Clippy Three Levels of Interactivity
– Personalization The majority of users use the default setting of change a small subset of the possible features
– 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
– 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
The authors conclude that people are willing to give up partial control if the reward in usefulness is great enough
How could we deal with the imperfect/probabilistic context data? Fuzzy Logic Context Data Abstraction
What could be the Killer Application? What could we mine from the log data?
Support Rules
Peer to Peer vs. Centralized System
L Barkhuus, A Dey, Is Context-Aware Computing Taking Control Away from the User? Three Levels of Interactivity Examined,2003
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Layered Conceptual Framework with Core Components
Foundation Layer:SensorsData/Rule MiningRelational DatabaseNetwork
Semantic Technology Layer:Ontology RepositoryInference Engine
Service & Application Design Layer:
Context-Aware Services:
Context Acquisition DeviceCommunication
Data Management & Mining
Context OntologyModeling
Context Fusion & Abstraction
Rule based Action Triggering
Ontology DataStorage
& Management
Low-levelData Modeling
Context-Aware Personalized Contents Push
Seamless Device
Switching
Automatic Device
ConfigurationDecision Support
& SuggestionContext Aware User Interface
UbiquitousIntelligentSeamless
Domain-specific Context Data
ModelingRule
DefiningService
Algorithm Implementation
Privacy & Security Policy
Defining
Private Scalable
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Conclusions We talked about
Motivation History of Context-aware Computing Categories of Context-aware Applications Design Principle Examples of Context-aware Systems Criteria & Discussion
What will be the future Context-aware System? A Context-aware system with
– Better scalability and performance– Utilizing historical context data (Rule mining, ...)– Better Security policies and privacy protection– Virtual and logical sensor support– Standard communication protocol and context model