1. CASS – Middleware for Mobile Context-Aware Applications Patrick Fahy Siobhan Clarke Trinity College Dublin, Ireland 2008.07.16 Summarized by Babar Tareen, IDS Lab., Seoul National University

2. Copyright  2007 by CEBT Introduction  CASS (Context-awareness sub-structure) is server based middleware  Provides support for Context aware applications on hand-held and other mobile devices  Supports high level context data abstraction  Separation of context based inferences and behaviors from application code  Allow an application’s context reasoning and behaviors to be changed without re-compilation 2

3. Copyright  2007 by CEBT Requirements for CASS  Support a large number of context sources  Provision for context history  Support for context interpretation For example raw temperature reading to reading in degree Celsius  Support High-level abstraction of contexts  Middleware must be event based so that application does not ne ed to poll for context changes  Middleware must be extensible  Support transparent use of distributed sources of context  Support the separation of application procedure from context-aw areness rules and behaviors 3

4. Copyright  2007 by CEBT Architecture 4  Sensor nodes are computers wit h sensors attached and may be mobile or static  Middleware being server based, allows use of a database and arti ficial intelligence components as required  Applications need not to commun icate with each individual source of context directly but only with th e middleware

5. Copyright  2007 by CEBT Implementation Details  CASS middleware uses a database for persistent data storage  Advantages of using database Data can be read and manipulated at a high level of abstraction usin g Structured Query Language (SQL) The database can be used to store, not only context, application an d user data but also domain knowledge in the form of context-aware ness rules and behaviors relevant to specific applications By providing a suitable interface to the database containing the cont ext inference rules, these rules could then be updated and changed by users rather than programmers  CASS inference engine uses forward chaining  CASS stores application knowledge base as database tables 5

6. Copyright  2007 by CEBT Applications  Two applications under development MALLET (Maintenance Assignment Listing Lightweight Electronic T ool) – Allows domestic and building maintenance tasks to be organized in cont ext-aware way STONE (Start ON Entrance) – Designed to avoid the awkward start to presentations and lectures invol ving slideshows 6

7. Copyright  2007 by CEBT Paper Evaluation  Good points Moving context sensors to separate computers and allowing the sen sors to communicate with the middleware allows any type of device, with or without context sensing capabilities, to run context-aware ap plications Because devices acquire context data from middleware, context dat a can be shared among multiple devices  Bad Points Only getting context related data may limit the possible application s cenarios for context-aware services. For example an application will be more interested in local temperature around the device and not t he temperature at some point where sensing node is deployed 7