Context-Awareness in Mobile Environments

1. Context-Awareness in Mobile Environments Gruia-Catalin Roman Mobile Computing Laboratory Department of Computer Science and Engineering 7 June 2002 (Philadelphia, PA)

2. MOBILE COMPUTING

21. Trends in Mobile Computing • Technology • Miniaturization • Wireless communication • Java • Society • Ubiquitous access • Increasing levels of mobility • Computing and communication melting into the fabric of society • Infrastructure • Enterprises • People

22. Physical Mobility • Fixed network • Nomadic computing • Ad hoc computing

23. New design constraints Frequent disconnection Unpredictable movement Asymmetric bandwidth Limited resources Short battery life Interesting opportunities Spatial knowledge Movement profile Increased demands Reasoning about behavior Connectivity maintenance Adaptation Research Implications

24. Logical Mobility • Code on demand • Remote evaluation • Mobile agents

25. Research Trends • Code on demand is made popular by Java • Mobile code languages (e.g., Oblique, Facile, Telescript) are losing ground • Mobile agent systems (e.g., Agent TCL) are an emerging new technology • Middleware is growing in practical importance

26. Mobility Paradigms • Continued access to remote resources • Delegation to mobile agents • Disconnected operation • Ad hoc grouping of people and devices • Mass mobility

27. Ad Hoc Network Challenge • No fixed network infrastructure • Transient interactions • Decoupled computing • Open environment • Physical and logical mobility • Frequent disconnections • Limited guarantees

28. Sample Applications • Highway information management • Disaster response • Military applications • Contamination zone exploration • Wireless anywhere classroom • Cave and mine exploration • Self-organizing office and factory • Video games in physical spaces

29. Rapid development of dependable mobile applications over ad hoc networks Formal models: precise semantics and analysis Coordination Models rapid development Middleware: easy dissemination Algorithms: feasible implementation Applications: empirical evaluation Mobile Computing Laboratory

30. Research Strategy • Formal models • Integrated perspective on physical and logical mobility • Pragmatic use of formal thinking • Precise semantics for coordination constructs • Formal verification of protocols and algorithms • Informal reasoning during the design process • Communication • High-level abstract coordination mechanisms • Mobility and location sensitive protocols • Programming • Decoupled style of computing • Context aware programming methods • Middleware supported application development

31. Recent Activities • Formal models of mobility • Mobile UNITY • CodeWeave • Coordination models • GVDS — Global Virtual Data Structures • Application-specific coordination models • Middleware for mobility • LIME • Coordination veneers over LIME • LIMELite • Algorithms and protocols for mobile computing • Mobile applications including peer to peer communication on highways

32. Mobile UNITY • Program • unit of modularity • unit of mobility • fully decoupled • Mobility • arbitrary physical and logical spaces • reduced to assignment • System • programs • small set of coordination constructs • Proof logic • minimal extension of UNITY Y X UNITY +  +unique names

33. Model Evaluation correspondentnode • Rich set of coordination constructs expressing transient and transitive interactions • Formal specification and verification of Mobile IP • Formal specification and verification of mobile code • Semantic basis for a new model of fine grained mobility (CodeWeave) • Reactive programming support for dynamic reconfiguration homeagent foreignagent mobilenode

34. Global virtual data structures (GVDS) Service provision (Jini) in ad hoc networks Event notification in ad hoc networks Ad hoc code repositories Administrative domain structures in ad hoc Coordination Models service usage service discovery service registration

35. A Middleware for Mobility — LIME federated tuple space • Profile • Linda-style coordination extended to ad hoc settings • Transparent data sharing based on connectivity • Atomic and transitive engagement and disengagement • Selective data sharing • Transparent tuple migration • Novel reactive constructs • Distribution • Open source • Available on SourceForge • Active efforts • LIMELite • Coordination veneers hosttuple space mobileagent

36. New algorithm design strategies for nomadic settings host as message paradigm FIFO communication/motion Message delivery adaptation of distributed snapshots Mobile tracking based on diffusing computations Termination detection formal derivation disconnected routing Mobile Algorithms mobile unit

37. Wireless chat room Decoupled game playing Commando games Cooperative work (puzzle) Technology transferFord Research, Detroit, MI smart intersections synchronized cruse control Applications

38. Context Awareness Revisited • Context awareness is a necessity in ad hoc mobility • Agility is important in highly dynamic environments • Small components rely on opportunistically available resources while available • Perception of context varies by task and situation • Large-scale deployment of context-aware middleware rests with asking for exactly what is needed, when it is needed, and nothing more • Transparent context management can simplify the programming task

39. Computational Model • Ad hoc network • Mobile host • Mobile agent • Object/Data

40. Context is extended beyond host boundaries Context is separated into task-specific views An agent may have multiple views Views may change over time Views are defined in terms of propertiesof the network, hosts, agents, and objects Active views may exhibit built-in behaviors (e.g., data migration) Agent-Centered Context referenceagent

41. Technical Considerations • Presentation style • coordination model amd semantics • Definition • declarative specification • expressive power • Computation • context discovery and maintenance • context evaluation infrastructure • Delivery vehicle • middleware framework

42. Perspectives on Context • Context-sensitive data structures • Context-sensitive references • Context-sensitive bindings • Context-sensitive events

43. D = distance to the first open EXXON gas station on the right … B = Internet access via a 1Mb connection within two hops P = closest laser printer within 50 ft. Declarative Context Specification EXXON 9.2 mil. lpr:john

44. Group membership masking unannounced disconnection location based protocols safe distance concept Network abstraction spatiotemporal services strictly monotonic metrics bounds Infrastructure Support

45. Points of Synergy • Executable specifications • Formal semantic analysis • Weak semantics and formal guarantees • Algorithm and protocol design and analysis • Novel routing protocols • Security mechanics • Common middleware frameworks

46. Conclusions • Mobility challenges our way of thinking • we explore novel uses of location information and more • A solid grounding in traditional distributed computing is a prerequisite for success • we leverage off past work on formal models and algorithms • Complexity demands an increasing reliance on pragmatic application of rigorous design technique • we focus on coordination models having precise semantics • Sensitivity to the market place and application demands is more important than ever • we emphasize application-driven empirical evaluation

47. Thank you … cs.wustl.edu/mobilab/