1. 2003.10.14UbiComp ’03 – Context Awareness Session liquid context-aware distributed queries jeffrey heer alan newberger chris beckmann jason i. hong group for user interface research university of california, berkeley

2. 2003.10.14UbiComp ’03 – Context Awareness Session the problem  monitoring context data is complicated by its distributed and dynamic nature, making application authoring more difficult a solution  push advanced support into the infrastructure  liquid : a query service supporting distributed, decentralized query processing over continuously changing context data, built atop Context Fabric roadmap

3. 2003.10.14UbiComp ’03 – Context Awareness Session context-aware computing leverage input such as sensor readings to  give computers awareness of physical and social environment  provide enhanced services by modeling the tasks or activities at hand context data includes the state of  people, places, objects, activities

4. 2003.10.14UbiComp ’03 – Context Awareness Session the problem we expect context data to be distributed, but under existing context-aware computing infrastructures dynamic data retrieval can become quite complicated… an example: say I’m hard at work on a research paper and I need to get feedback from my advisor. I want to know when he is in the building and is interruptible…

5. 2003.10.14UbiComp ’03 – Context Awareness Session a scenario (non- liquid ) select location.building.occupant where occupant.name = "James Landay" and occupant.interruptibility <= 3 the application must handle multiple network connections, subscriptions, and perform all intermediate data processing!

6. 2003.10.14UbiComp ’03 – Context Awareness Session solution: liquid push needed functionality into infrastructure liquid - context-aware query processing  distributed, streaming queries  dynamic query re-routing in response to context uses numerous innovations from the database community:  distributed databases (R*, Mariposa)  streaming databases (TelegraphCQ, Stream, Aurora)  semi-structured databases (Lore) ubicomp’s needs lie in this intersection!

7. 2003.10.14UbiComp ’03 – Context Awareness Session scenario revisited ( liquid style) select location.building.occupant where occupant.name = "James Landay" and occupant.interruptibility <= 3 query

8. 2003.10.14UbiComp ’03 – Context Awareness Session scenario revisited ( liquid style) select location.building.occupant where occupant.name = "James Landay" and occupant.interruptibility <= 3 query

9. 2003.10.14UbiComp ’03 – Context Awareness Session scenario revisited ( liquid style) select location.building.occupant where occupant.name = "James Landay" and occupant.interruptibility <= 3 query

10. 2003.10.14UbiComp ’03 – Context Awareness Session scenario revisited ( liquid style) select location.building.occupant where occupant.name = "James Landay" and occupant.interruptibility <= 3 query

11. 2003.10.14UbiComp ’03 – Context Awareness Session scenario revisited ( liquid style) result select location.building.occupant where occupant.name = "James Landay" and occupant.interruptibility <= 3

12. 2003.10.14UbiComp ’03 – Context Awareness Session scenario revisited ( liquid style) select location.building.occupant where occupant.name = "James Landay" and occupant.interruptibility <= 3 query

13. 2003.10.14UbiComp ’03 – Context Awareness Session liquid concepts entity type paths  a naming mechanism for context data  e.g., location.building.occupant query specification  how to issue a query  XML-based query language query execution  how a query is evaluated

14. 2003.10.14UbiComp ’03 – Context Awareness Session liquid concepts: query execution

15. 2003.10.14UbiComp ’03 – Context Awareness Session applications: room aware

16. 2003.10.14UbiComp ’03 – Context Awareness Session conclusion liquid provides distributed, continuous queries over collected context data liquid provides dynamic query re-routing in response to changing context take-home message: important to leverage synergies between UbiComp and Database communities.

17. 2003.10.14UbiComp ’03 – Context Awareness Session Questions? Jeffrey Heer jheer@cs.berkeley.edu Alan Newberger alann@cs.berkeley.edu Chris Beckmann beckmann@cs.berkeley.edu Jason I. Hong jasonh@cs.berkeley.edu liquid is bundled with the context fabric distribution -context fabric home: http://guir.berkeley.edu/cfabric http://guir.berkeley.edu/cfabric

18. 2003.10.14UbiComp ’03 – Context Awareness Session entity type paths An entity type path specifies a ContextTuple to be retrieved at the end of a sequence of infospaces. location.building.occupant Each infospace in the sequence is specified by its relation to the preceding infospace, and addressed by an entity-link.

19. 2003.10.14UbiComp ’03 – Context Awareness Session entity type paths location.building.occupant

20. 2003.10.14UbiComp ’03 – Context Awareness Session entity type paths location.building.occupant

21. 2003.10.14UbiComp ’03 – Context Awareness Session entity type paths location.building.occupant

22. 2003.10.14UbiComp ’03 – Context Awareness Session query specification queries are specified using XML syntax future work: a high-level query language that maps down to this intermediate XML rep. location.occupant email

23. 2003.10.14UbiComp ’03 – Context Awareness Session result items result items == collection of context tuples + query metadata (timestamp, status) query result status types  inserted new tuple inserted into an infospace  deleted tuple deleted from an infospace  updated tuple updated in infospace (and still matches query)  exited tuple updated in infospace (and no longer matches)  expired tuple fell out of window watched by liquid