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Context-Awareness in Mobile Environments

Explore the trends, challenges, and opportunities in mobile computing, including code on demand, mobile agents, and middleware. Learn about formal models, coordination mechanisms, and algorithms for dependable mobile applications.

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Context-Awareness in Mobile Environments

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  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

  3. 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

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

  5. 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

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

  7. 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

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

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

  10. 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

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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

  18. 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

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

  20. 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

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

  22. 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

  23. 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

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

  25. 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

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

  27. 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

  28. 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

  29. Thank you … cs.wustl.edu/mobilab/

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