1. Context-Awareness on Mobile Devices – the Hydrogen Approach Sangkeun Lee

2. Context-Awareness for Mobile Devices Support context-awareness for considering –Special requirements of mobile devices regarding the limitations of network connections, computing power Requirements for an architecture of a framework to support context-awareness on mobile devices –Lightweightness –Extensibility –Robustness –Meta-Information –Context-Sharing Separiting the concerns of context sensing from the application is needed

3. Hydrogen Context-Framework Three architecture –Application Layer –Management Layer : Context Server Provide simple methods for the applications for retrieving or subsribing to a context –Adaptor Layer Responsible to get information from sensors –Reusability, Exchangeability of sensors & adoptors

4. Implementation – the Hydrogen Approach Prototype Implementation –PersonalJava virtual machines Jeode, J2ME, iPAQs, PocketPC 2002 Context –Time, Location, Device, User, Network ContextClient –Responsible for communication : open ports, queries data Context Server –Java Executable object –Communication in two forms : XML-streams, serialized Java objects Extensibility –toXML(), fromXML() Open Issues –Comprehensive Context Model –XML Protocols –Context Sharing

5. CASS- Middleware for Mobile Context-Aware Applications Sangkeun Lee

6. General CASS (Context-awareness sub-structure) –Server based extensibile middleware to support context-aware applications on mobile devices High-level context data abstraction Separation of context based inferences from application code Configurable by users

7. CASS Overview Requirements –Support many of context sources –Provision for context history –Support for context interpretation –Support higher-level abstraction of contexts –Should be event-based, extensible framework –Transparent use of distributed sources of context –Separation of application procedure Architecture –CASS Applications do not need to store low-level details of context sources and communicate with individual source –CASS Middleware does that Design –SensorListener listens for updates and stores context information –ContextRetriever retrieves stored context –ChangeListener allows a mobile computer to listen for context events

8. Data Management & Inference CASS uses a database for persistent data store –The database is server-based that does not suffer from the storage space and performance –Data can be read and manipulated using SQL –Not only context, domain knowledge and rules can be stored too Inference Engine –Forward Chaining