A Survey on Context-Aware Computing Center for E-Business Technology Seoul National University Seoul, Korea 이상근, 이동주, 강승석, Babar Tareen Intelligent Database Systems Lab School of Computer Science & Engineering Seoul National University, Seoul, Korea

Copyright  2008 by CEBT Introduction  We gathered papers below and categorized into 4 groups – Survey Papers (8) – Context Models (7) – Domain Dependent Applications (3) – Architectural Approaches (17)  Survey on Survey Papers A Survey on Context-aware Systems (2007) Middleware for Distributed Context-Aware System (2005) Is Context-Aware Computing Taking Control Away from the User?- Three Levels of Interactivity Examined (2003) Towards a Better Understanding of Context and Context-Awareness (2000) A Survey of Context-Aware Mobile Computing Research (2000) Context-Aware Computing Applications (1994) Semantic Tech & Context - 2

Copyright  2008 by CEBT History of Context-Aware Computing  Active Badge Location System (Wang et al., 1992)  Term ‘Context-aware’ appeared in Schilit and Theimer(1994) Authors describe context as location, identities of nearby people, objects, and changes to those objects  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  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 between a user and an application, including the user and the application themselves Semantic Tech & Context - 3

Copyright  2008 by CEBT Three Levels of Interactivity  Personalization Common feature of computing applications Increased level of tailoring in software The majority of users use the default setting of change a small subset of the possible features  Active and Passive Context-awareness Using Chen and Kotz’s definition of context-awareness 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 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

Copyright  2008 by CEBT History of Context-Aware Computing  Burnett (2003) and Gustavsen (2002) External and internal  Hofer et al. (2002) Physical and logical  Dey and Abowd, 2001 Entities: Places, People, things Attributes: identity, location, status, time, … Semantic Tech & Context - 5 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 Categories of Context Aware Applications  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 6

Copyright  2008 by CEBT Design Principles - Architecture  Chen (2004) presents three different approaches on how to acquire contextual information 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) Semantic Tech & Context - 7 Layered conceptual framework for context-aware systems Physical Sensors – hardware sensors Virtual Sensors – context data fro apps or services Logical Sensors – combine physical & virtual sensors with additional information from DBs or other sources

Copyright  2008 by CEBT Design Principles – Context Models  Models Key-Value models Markup scheme models – Use a hierarchical data structure consisting of markup tags Graphical models – Use UML to represent context information Object oriented models Logic based models Ontology based models  Attributes Context type Context value Time stamp Source Confidence 8 SimplicityFlexibilityGenericityExpressiveness Requirements

Copyright  2008 by CEBT Existent systems and frameworks  Three types of existing context-aware systems Location-aware systems Context-aware systems Context-aware frameworks – Context Managing Framework (2003) – SOCAM (2004) – CASS (2004) – CoBrA(2003) – Context Toolkit (2000) – Hydrogen project (2002) – CORTEX (2004) – Gaia (2002) – … Semantic Tech & Context - 9 ArchitectureResource discoverySensingContext model Context processingHistorical context dataSecurity and privacy

Copyright  2008 by CEBT Existent systems and frameworks

Copyright  2008 by CEBT More Criteria & Conclusion  The direct comparison of the named systems and frameworks shows their similarity concerning the layered structure  Mainly use physical sensors only  Lack of security and privacy modules  Standardization is required  Scalability issues

Copyright  2008 by CEBT Survey Schedule  Paper Selection(1 week)  Survey (4 weeks) CASS, Hydrogen Gaia, SOCAM Context Toolkit, CORTEX Context Fusion Networks, The Context Fabric Other Architectures  Context-Aware Computing Conceptual Framework (1~2 weeks) Generalize technology components Technology Map about Context-Aware Computing Conceptual Framework Technology Roadmap  Evaluation (2~3 weeks) Scenario Set-up Comparison Table Evaluate each approach Semantic Tech & Context - 12