1 / 46

A Software Engineering Perspective on Context-Awareness in Ad Hoc Mobile Networks

A Software Engineering Perspective on Context-Awareness in Ad Hoc Mobile Networks. Christine Julien Mobile Computing Laboratory Washington University in Saint Louis December 21, 2019. Motivation. Simplify mobile application development Individually address application-specific needs

ivelisse
Télécharger la présentation

A Software Engineering Perspective on Context-Awareness in Ad Hoc Mobile Networks

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. A Software Engineering Perspective on Context-Awareness in Ad Hoc Mobile Networks Christine Julien Mobile Computing Laboratory Washington University in Saint Louis December 21, 2019

  2. Motivation • Simplify mobile application development • Individually address application-specific needs • Dynamically gather context information from the network • Seamlessly adapt to environmental changes • Transparently help programmers cope with problems inherent in ad hoc networks Christine Julien

  3. Ad Hoc Network Challenges • Form opportunistically • Change rapidly in response to mobility • Rely on no fixed infrastructure • Provide transient interactions • Foster decoupled computing • Embody open environments with limited guarantees Christine Julien

  4. Computational Model • Ad hoc network • Host (mobile or stationary) • Defines location in physical space • Agents/Application Components • Unit of mobility residing on a host • Data • Owned and generated by each agent Host 2 Host 1 Host 3 Christine Julien

  5. Overview • Context-aware computing • EgoSpaces conceptual model • EgoSpaces middleware • Network abstractions • Conclusions and future work Christine Julien

  6. Context-Aware Computing:The Need for Context • Software and hardware constantly move and change • Applications must opportunistically adapt • Perception of context varies by application • Current solutions: • Use basic types of context information in specific ways • Fieldwork tools, guide tools • Provide access to only a single component’s sensors at a time • Context Toolkit, Context Fabric • Support only local or symmetric interactions • MARS, LIME Christine Julien

  7. Traffic Collision Context-Aware Computing:Rethinking Applications (1) Christine Julien

  8. Context-Aware Computing:Rethinking Applications (2) Christine Julien

  9. Context-Aware Computing:Rethinking Applications (3) Charlie Angie Christine Julien

  10. Context-Aware Computing:Novel Notion of Context • Flexible adaptation in dynamic environments • Scope that extends beyond the local host • Generalized interaction with context types • Context needs vary by task and situation • Asymmetric context interaction • Multiple contexts evolving over time • Context computation must be scalable • Explicit control over the scope, size, and cost Christine Julien

  11. Overview • Context-aware computing • EgoSpaces conceptual model • EgoSpaces middleware • Network abstractions • Conclusions Christine Julien

  12. EgoSpaces Conceptual Model:The View Concept • Maximal context contains all available data • A view is a projection of the maximal context • Egocentric abstraction of operating context • Tailored to an application’s individual needs • Allow agent to control scope of views • Ease program development • Minimize performance penalties Host 2 Host 1 Reference agent’s view: yellow data within one hop Host 3 Christine Julien

  13. EgoSpaces Conceptual Model:Declarative View Specification • Allows simple yet meaningful view definitions • Restrict context based on properties of the network, hosts, agents, and data All location data owned by collision warning agents on cars within 100 meters of my current location • Facilitate transparent context maintenance • Rely on underlying middleware for context maintenance tasks Roman, G.-C., Julien, C., and Murphy, A. L., "A Declarative Approach to Agent-Centered Context-Aware Computing in Ad Hoc Wireless Environments,” Software Engineering for Large-Scale Multi-Agent Systems, LNCS 2603, April 2003. Christine Julien

  14. EgoSpaces Conceptual Model:View Interaction • Present view contents as tuple space • Allows use of traditional Linda-like operations • Content-based pattern matching for tuple retrieval • retrieve tuples (rd) • remove tuples (in) • Can affect overlapping views • Atomic blocking and probing operations Julien, C., and Roman, G.-C., "Egocentric Context-Aware Programming in Ad Hoc Mobile Environments," in Proceedings of FSE-10, November 2002. Christine Julien

  15. EgoSpaces Conceptual Model:Consistency Concerns • Transactional semantics (e.g., money transfers) • Strong application guarantees • Can be expensive • Use atomic Linda-like operations • “Best-effort” semantics (e.g., traffic) • Variety of implementations • Application chooses semantics based on its particular situation • Use scattered probing operations Christine Julien

  16. EgoSpaces Conceptual Model:Reactive Views • Facilitate behavioral adaptation • Agents respond to presence of certain tuples • Associate application-level reaction to the appearance of a tuple • Scheduling modalities correspond to consistency requirements • Eager semantics provide transactional guarantees • Lazy semantics provide fewer guarantees • Allow more flexible implementation • Increase performance Christine Julien

  17. EgoSpaces Conceptual Model:Active Views • Capture natural context interactions • Transparent data migration • Automatic duplication • Event capture • Extensibility • Simplify programming • Programming abstractions • Reduced code size migrate Julien, C. and Roman, G.-C., "Active Coordination in Ad Hoc Networks," to appear in Proceedings of Coordination 2004. Christine Julien

  18. EgoSpaces Conceptual Model:Access Control Requirements • Ad hoc networks are open environments, yet agents may need to restrict data access • No permanent trusted central server • Current work • Administrative domains • Mobile Ambients, SEAL • Specialized type systems • KLAIM • Fine-grained access control • SECOS • Must scale to large systems • Must address needs of individualized agents Christine Julien

  19. EgoSpaces Conceptual Model:Access Control Provision • Agent specified access control function • Limits access based on agent properties • Allows fine-grained access control • Individualized to particular application’s needs • Reference agent provides credentials and intended operations • Access control functions evaluated on a per-tuple basis to determine inclusion in the view • Can be used to define administrative domains Christine Julien

  20. Overview • Context-aware computing • EgoSpaces conceptual model • EgoSpaces middleware • Network abstractions • Conclusions Christine Julien

  21. EgoSpaces Middleware:Why Middleware? • Speed up application development in ad hoc networks • Enhance level of programming abstraction • Provide generic and flexible context operations • Shift complex tasks to underlying infrastructure • Facilitate rapid dissemination and adoption • Proven solutions for other domains • Distributed object systems • CORBA, Jini, DENO • Mobile agent systems • Aglets, D’Agents, Code • Coordination systems • LIME, MARS, Jedi Christine Julien

  22. EgoSpaces Middleware:EgoSpaces Middleware • Programming interface simplifies application development burden • Allows declarative view specification • Presents view contents as tuple space • Provides standard Linda tuple space operations on view definitions • Includes light-weight implementations of tuple space operations • Provides tailored access control Christine Julien

  23. EgoSpaces Middleware:EgoSpaces Architecture • Application provides declarative view specifications • Middleware • Discovers neighbors • Monitors context sensors • Provides data contents of context to application through view abstraction application EgoSpaces ELights network abstractions sensor monitoring discovery message sensing ad hoc physical network Christine Julien

  24. EgoSpaces Middleware:Demo Application • Application-specific view restriction • Hop-count based metric • File-size restriction • Content-based selection from view • Songs displayed based on desired properties • Reactive programming allows downloads to resume Christine Julien

  25. EgoSpaces Middleware:Simplifying Application Development • Abstracts network for application programmer • Removes concern for low-level network and communication concerns • Provides high-level, abstract definition of needs • Maintains contents of views as the environment changes • Programmer does not have to persistently poll • Shifts developer focus to key components of applications • User interface design • Local data storage and representation Christine Julien

  26. Overview • Context-aware computing • EgoSpaces conceptual model • EgoSpaces middleware • Network abstractions • Conclusions Christine Julien

  27. 5mi Network Abstractions:Restricting the Network • Defining a view requires limiting participating hosts • e.g., all hosts within five miles or within three hops • Consider the overhead in defining such a network • Deal with volatility of ad hoc networks • Unannounced disconnection • Unpredictable reconnection • Heterogeneous devices Roman, G.-C., Julien, C., and Huang, Q., "Network Abstractions for Context Aware Mobile Computing," in Proceedings of ICSE, May 2002. Christine Julien

  28. Network Abstractions:Solution Overview • Represent the ad hoc network as a graph • Abstract properties of nodes and links to weights on edges in this graph • Calculate the cost of paths from the reference node • Determine the shortest path to each node and build a tree • Limit this tree using a bound, D Christine Julien

  29. j i ij j i Network Abstractions:Weight Assignment • Individualized for an application • Abstracts varied properties of hosts and links • Host properties form i; link properties form ij • i includes battery power, CPU power, location, etc. • ij includes physical distance, bandwidth, throughput, etc. • Edge weights combine link properties and the properties of the connected nodes mij = (i, j, ij) Christine Julien

  30. Network Abstractions:Computing Path Cost • Assuming each link has a single weight (mij), an application can define a generalized cost function: • v0(Pk) = Cost(v0(Pk-1), mk-1,k) • v0(v0) = 0 • Cost function must be strictly increasing along a path Christine Julien

  31. Network Abstractions:Limiting the Scope 3 • Define a subtree of the network by placing a bound on the cost of each path • Bound is useful only if shortest path cost is strictly increasing • Allows reference to restrict computation to a subnet 1 2 2 1 1 0 1 2 1 2 1 1 Note: All links have a weight of 1 Christine Julien

  32. Network Abstractions:Context Calculation Protocol • Service new queries • Respond at the application level • Remember cost, parent, sequence number, and information about the computation • Propagate the query • Service shorter distances (same sequence number) • Remember cost and new parent • Propagate query • Disregard longer distances (same sequence number) • But remember cost and parent if within bound • Halt when computation reaches boundary • Based on traditional ad hoc routing protocols Christine Julien

  33. (r, 4, …) (r, 2, …) (b, 5, …) [2, r, …] [2, r, …] [2, r, …] [4, r, …] [4, r, …] [2, r, …] [3, a, …] [3, a, …] {(r,2), (b,5)} {(r,2), (b,5)} {(r,2)} {(r,4)} {(r,4)} {(r,4),(a,3)} {(r,4), (a,3)} {(r,2), (b,5)} (a, 3, …) (b, 5, …) (b, 4, …) [4, b, …] [5, b, …] [5, b, …] {(b,4)} {(b,5)} {(b,5)} Network Abstractions:Protocol Example Query= (source, new cost, …) State= [cost, parent, ...] {(neighbor, cost through neighbor), …} Bound = 6 Cost = additive [0, null, …] r 4 2 1 a b 5 1 4 c d Christine Julien

  34. Network Abstractions:Context Maintenance Protocol • Persistent queries require context maintenance • React to increase in link weight • If parent, adjust cost and propagate information • Otherwise, update local information • React to decrease in link weight • If non-parent link, recalculate cost for neighbor on the other end • Handle “count-to-infinity” problem • Store entire shortest path at each hop • Regain resources when context is no longer used Christine Julien

  35. [2, r, …] [3, a, …] [2, r, …] [3, a, …] {(r,2), (b,10)} {(r,2), (b,5)} {(r,2)} {(r,4)} {(r,4),(a,3)} {(r,4), (a,8)} [2, r, …] [4, r, …] (b, 5, …) [4, b, …] [5, b, …] {(b,4)} {(b,5)} Network Abstractions:Maintenance Example Query= (source, source cost, new cost, …) State= [cost, parent, …] {(neighbor, cost through neighbor), …} Bound = 6 Cost = additive [0, null, …] r 4 2 6 1 a b 5 1 4 d c Christine Julien

  36. Network Abstractions:Evaluation • Simulation using ns-2 network simulator • 100 node network in 1000x1000m2 space • Vary network density by changing transmission range • Using random waypoint mobility model adapted to avoid speed degradation • Metrics • Context consistency • Settling time (at most 35ms) • Percentage of useful broadcasts Christine Julien

  37. Network Abstractions:Context Building Consistency (1) • Good consistency for reasonably sized contexts one-hop context two-hop context Percentage of context receiving message three-hop context four-hop context Transmission range (meters) Christine Julien

  38. Network Abstractions:Context Building Consistency (2) • Consistency >80% with increased network load five context definitions one context definition Percentage of context receiving message ten context definitions Transmission range (meters) Christine Julien

  39. Network Abstractions:Useful Broadcasts • Efficiency decreases with increasing density one-hop context two-hop context Percentage of useful broadcasts three-hop context four-hop context Transmission range (meters) Christine Julien

  40. Conclusions • Melding of context-awareness and ad hoc networks • Novel notion of context • Individualized declarative specification • Includes general facets of the environment • Extended in scope to remote components • Asymmetric context interactions • EgoSpaces model and middleware • Supporting algorithms and protocols Christine Julien

  41. Contributions (1) • Algorithms for ad hoc mobile computing • Network abstractions • Consistent group membership R R R a a r b b Huang, Q., Julien, C., and Roman, G.-C., "Relying on Safe Distance to Achieve Strong Partitionable Group Membership in Ad Hoc Networks," to appear in IEEE Transactions on Mobile Computing. Christine Julien

  42. Contributions (2) • Middleware for context-awareness • Addressing software engineering concerns of mobile environments • Facilitating rapid development of mobile applications • Bringing application development to the hands of novice programmers Handorean, R., Payton, J., Julien C., and Roman, G.-C., "Coordination Middleware Supporting Rapid Deployment of Ad Hoc Mobile Systems", in Proceedings of the 1st ICDCS Workshop on Mobile Computing Middleware (MCM03), May 2003. Christine Julien

  43. Contributions (3) • Formal models of context-aware and mobile computing • Specification and refinement using Mobile UNITY • Building Context UNITY for direct reasoning about context-aware systems • Roman, G.-G., Julien, C., and Payton, J., "A Formal Treatment of Context-Awareness," (invited paper) to appear in Proceedings of FASE 2004. • Julien, C., Payton, J., and Roman, G.-C., "Reasoning About Context-Awareness in the Presence of Mobility," in Proceedings of FOCLASA, September 2003. • Roman, G.-C., Julien, C., and Huang, Q., "Formal Specification and Design of Mobile Systems," in Proceedings of FMPPTA'2002, April 2002. Christine Julien

  44. Future Plans • Addressing ad hoc network and communication concerns in software engineering • Transactional programming in ad hoc networks • Tailored communication and coordination paradigms for applications in ad hoc networks • Context-aware routing and communication • Applying formal methods to context-aware environments • Reasoning about mobile and context-aware applications through formal notation and proof logic Christine Julien

  45. Questions? http://www.cse.wustl.edu/~julien julien@wustl.edu Christine Julien

  46. Publications www.cse.wustl.edu/~julien • Roman, G.-G., Julien, C., and Payton, J., "A Formal Treatment of Context-Awareness," (invited paper) to appear in Proceedings of Fundamental Approaches to Software Engineering 2004. • Julien, C. and Roman, G.-C., "Active Coordination in Ad Hoc Networks," to appear in Proceedings of Coordination 2004. • Huang, Q., Julien, C., and Roman, G.-C., "Relying on Safe Distance to Achieve Strong Partitionable Group Membership in Ad Hoc Networks," to appear in IEEE Transactions on Mobile Computing. • Julien, C., Payton, J., and Roman, G.-C., "Reasoning About Context-Awareness in the Presence of Mobility," in Proceedings of the 2nd International Workshop on Foundations of Coordination Languages and Software Architectures (FOCLASA03), September 2003. • Handorean, R., Payton, J., Julien C., and Roman, G.-C., "Coordination Middleware Supporting Rapid Deployment of Ad Hoc Mobile Systems", in Proceedings of the First International ICDCS Workshop on Mobile Computing Middleware (MCM03), May 2003. • Roman, G.-C., Julien, C., and Murphy, A. L., "A Declarative Approach to Agent-Centered Context-Aware Computing in Ad Hoc Wireless Environments (extended version)," Software Engineering for Large-Scale Multi-Agent Systems, A. Garcia et. al. (editors), LNCS 2603, April 2003. • Julien, C., and Roman, G.-C., "Egocentric Context-Aware Programming in Ad Hoc Mobile Environments," in Proceedings of FSE-10, November 2002, pp. 21-30. • Roman, G.-C., Julien, C., and Huang, Q., "Network Abstractions for Context Aware Mobile Computing," in Proceedings of the 24th International Conference on Software Engineering (ICSE'02), Orlando, FL (USA), May 2002, pp. 363-373. • Roman, G.-C., Julien, C., and Murphy, A. L., "A Declarative Approach to Agent-Centered Context-Aware Computing in Ad Hoc Wireless Environments," in the 1st International Workshop on Software Engineering for Large-Scale Multi-Agent Systems (SELMAS'2002), May 2002. • Roman, G.-C., Julien, C., and Huang, Q., "Formal Specification and Design of Mobile Systems," in Proceedings of FMPPTA'2002, April 2002. Christine Julien

More Related