UbiCom Book Slides

1. UbiCom Book Slides Chapter 7 Context-Aware Systems (Part A: Contexts & the Context-Aware Lifecycle) Stefan Poslad http://www.eecs.qmul.ac.uk/people/stefan/ubicom Ubiquitous computing: smart devices, environmentsand interaction

2. Chapter 7: Overview Chapter 7 focuses on: • Internal system properties: context-awareness • External interaction with any type of environment • Focussing more on physical environment • A lesser extent focussing on ICT environment Ubiquitous computing: smart devices, environments and interaction

3. Related Chapter Links • Context-awareness of human environment (iHCI) and person-awareness and user context acquisition (Chapter 5) • Environment context acquisition: sensors (Chapter 6) • Environment context control: controllers (Chapter 6) • Event-based system models for context-awareness (Chapter 3) • Goal-based models & sequential environment models (Chapter 8) • Content adaptation for mobile terminals (Chapter 4) • UI techniques adapted for use in small and large displays discussed (Chapter 5) Ubiquitous computing: smart devices, environments and interaction

4. Chapter 7: Overview The slides for this chapter are also expanded and split into several parts in the full pack • Part A: Contexts & the Context-Aware Lifecycle • Part B: Context Adaptation Design • Part C: Spatial Awareness 1 • Part C: Spatial Awareness 2 • Part E: Mobile Awareness • Part F: Temporal Awareness & Composite Context Awareness Ubiquitous computing: smart devices, environments and interaction

5. Lecture Outline • Types of Context and Context Properties  • Context Aware Life Cycle • Context Adaptation • Spatial-Awareness • Mobile User Context Awareness: Call Routing • Content Adaptation for Mobile Terminals • Temporal awareness • Composite Context Awareness Ubiquitous computing: smart devices, environments and interaction

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7. Context Aware System versus Sensor-based System Ubiquitous computing: smart devices, environments and interaction

8. Contexts • A context represents the state or situation in the environment of a system that affects that system’s (application specific) behaviour • There are many definitions of context • There are several dimensions or properties to characterise contexts • There are many definitions of how to make systems aware of changes in their context: context awareness • Context-awareness is considered to be one of the fundamental properties of UbiComp systems and is a key property of smart environments. Ubiquitous computing: smart devices, environments and interaction

9. Defining Contexts: Concrete In terms of membership of some set of contexts • Location, identities of nearby people, objects and changes to those objects • Applications • External environment: physical, human, virtual • Awareness of internal (self) context may also be useful • What, who, where, when, how it is accessed and why, context is useful (Morse et al. (2000) Ubiquitous computing: smart devices, environments and interaction

10. Types of Context Ubiquitous computing: smart devices, environments and interaction

11. Context Types: By Application • We can classify context-awareness in terms of types of applications? • Mobility context-aware • Location aware • Time aware Ubiquitous computing: smart devices, environments and interaction

12. Lecture Outline • Types of Context & Context Properties • Context Aware Life Cycle  • Context Adaptation • Spatial-Awareness • Mobile User Context Awareness: Call Routing • Content Adaptation for Mobile Terminals • Temporal awareness • Composite Context Awareness Ubiquitous computing: smart devices, environments and interaction

13. Life-cycle for Context Awareness • Capture Physical Context • Capture User Context • Context Processing • Adapt to Context • Manage contexts Ubiquitous computing: smart devices, environments and interaction

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15. User Context Creation • Acquisition of user context: this can be derived from user’s application tasks • Policy creation: created from user’s tasks to determine how a user context is mediated by environment contexts • Encapsulation and abstraction: of the user context • Sharing the user context so that it can be distributed and accessed. Ubiquitous computing: smart devices, environments and interaction

16. Environment Context Creation / Capture • Acquisition: • Encapsulation: • Abstraction: • Filtering: • Sharing: Ubiquitous computing: smart devices, environments and interaction

17. Context Processing N.B Context acquisition may involve some context pre-processing, here the focus is on context post-processing. Context post-processing enables: • Context-composition: • Context Mediation: • Context Adaptation: Ubiquitous computing: smart devices, environments and interaction

18. Context Composition: Motivation Context composition may also be driven by the need to: • Improve acquisition accuracy for the context • Improve filtering and adaptation of content • Composite contexts are in inherent an application Ubiquitous computing: smart devices, environments and interaction

19. Context Composition: Challenges • Handling heterogeneity of representation • Handling heterogeneity of meaning • Mediating and coordinating context aggregation • Ordering the adaptation to individual contexts • Different weightings for combining contexts • Handling uncertainty in combining contexts Ubiquitous computing: smart devices, environments and interaction

20. Context Composition, Heterogeneous Contexts & Interoperability Context-aware systems may depend on & combine: • multiple representations for a single context • . • multiple representations of multiple contexts • Multiple representations determined independently by different applications & users Ubiquitous computing: smart devices, environments and interaction

21. Context Composition, Heterogeneous Contexts & Interoperability • Determination of a proposed joint context for meeting can be complex • Challenge here: to harmonize or standardize annotation so that they would be consistent used by all users. • Security, e.g., access control could be useful in certain applications to protect privacy or to limit access, Ubiquitous computing: smart devices, environments and interaction

22. Context Management • Discovery: directory services enable context sources, stores and users to be registered and discovered. • Storage: of context data into some data resource, may include • … • Sharing of environment and goal contexts • Access control: • . Ubiquitous computing: smart devices, environments and interaction

23. Lecture Outline • Types of Context and Context Properties • Context Aware Life Cycle • Context Adaptation  • Spatial-Awareness • Mobile User Context Awareness: Call Routing • Content Adaptation for Mobile Terminals • Temporal awareness • Composite Context Awareness Ubiquitous computing: smart devices, environments and interaction

24. Context Adaptation: Passive vs Active • Passive context adaptation system • Context is presented to users • Context-based tagging (chapter 6) • System is not active in terms of adapting • Active context-adaptation system • Adaptation to context performed by the UbiCom system, not human users. • Hybrid context adaptive system • Human user guides or corrects the automatic adaptation Ubiquitous computing: smart devices, environments and interaction

25. Context Adaptation Models Event-based Models (Chapter 3) • Context-awareness links context producer to a context-consumer or context-adapter • EDA is also similar to a Reactive intelligent system • See Chapter 8 • How do we limit the types of interest? Goal-based Models • Use a (planned) application or user goal to limit the set of current contexts which are useful • Relation of current context to goal context is fundamental Ubiquitous computing: smart devices, environments and interaction

26. Context-aware Application: Location (context) awareness • Goal context • Current context • Context Path • Constraints • Travel to the destination location • Current location • Planned path from the current to destination location • Not to deviate too far from the anticipated or planned position context; Ubiquitous computing: smart devices, environments and interaction

27. Context-aware Application: Location (context) awareness Ubiquitous computing: smart devices, environments and interaction

28. Context Aware Design Issues • Context Representation  • Use of Current versus Past Contexts • Context Determination • Static versus Dynamic CA • Active versus Passive Context Adaptation (done) • Heterogeneous Contexts & Interoperability • Context Composition Ubiquitous computing: smart devices, environments and interaction

29. Context Representations What type of data structures should be used to model contexts? • Key-Value pairs • Hierarchies / Markup Schemes, e.g., XML • Graphs • Object Oriented (o-o) • Logic Based: support reasoning about context • Strong Ontology Which of these is best? Why? Ubiquitous computing: smart devices, environments and interaction

30. Use of Current Context vs. use of Context History • Simplest type of context-aware system • Uses the current context, the current state, episodic, environment • Operates in an environment that is fully observed and deterministic • But context history can also be used • See Chapter 8 for more in-depth treatment of environments Ubiquitous computing: smart devices, environments and interaction

31. CA Design issues: Context Determination • Context determination: acquisition, accuracy particularly of user context can be complex • Active versus passive context acquisition • Single shot (static) versus dynamic acquisition • Heterogeneous context representation (syntax) and semantics, interoperability • Context distribution: Local context producer but remote context consumer Ubiquitous computing: smart devices, environments and interaction

32. User Context Determination 4 approaches • Combine several low-level sensor inputs to better infer user context, • Can Query user profile or model: abstraction that characterises the user, preferences the user expresses, • Ask users to define their own context. • Observing user interaction Ubiquitous computing: smart devices, environments and interaction

33. Static versus Dynamic CA • Static environment context • Dynamic environment context: Ubiquitous computing: smart devices, environments and interaction

34. Context Adaptation Benefits • Many useful Applications: • Reduces information overload on users • Lessen cognitive load on users • Filter information to fit a mobile device's limited and physically moving display, • Disabled people • Improve Regulation & Control Ubiquitous computing: smart devices, environments and interaction

35. Context-awareness: Challenges • 1. User Contexts may be incorrectly, incompletely, imprecisely determined or predicted, ambiguous • 2. Environment Contexts may be incorrectly, incompletely, imprecisely defined, determined or predicted. • 3. Contexts may exhibits a range of spatial-temporal characteristics • 4. Contexts may have alternative representations • 5.Contexts may be distributed and partitioned, composed of multiple parts that are highly interrelated • 6. Contexts may generate data huge volumes • 7. Context sources and local processes often need to embedded in a low resource infrastructure • 8. Context use can reduce the privacy of humans • 9. Awareness of context shifts can distract users Ubiquitous computing: smart devices, environments and interaction

36. Lecture Outline • Types of Context and Context Properties • Context Aware Life Cycle • Context Adaptation • Spatial-Awareness • Mobile User Context Awareness: Call Routing • Content Adaptation for Mobile Terminals • Temporal awareness  • Composite Context Awareness Ubiquitous computing: smart devices, environments and interaction

37. Spatial-Awareness Overview • Trigger spatial-aware services • Sense / determine current Location • Determine the spatial context • Service adaptation: adapt spatial information view w.r.t. to location Ubiquitous computing: smart devices, environments and interaction

38. Spatial-Aware Applications Applications which trigger use of spatial aware • Navigation, e.g., I'm lost, where is nearest Metro station? • Notification of context change: e.g. traffic queue ahead, change route.. • Querying location context, e.g. What speed limit on this road? • Personal Emergency: e.g. medical and Roadside • Emergency Service Operations: e.g., Are flammables nearby? • Enterprise Asset Tracking: e.g. “Where is water supply? • Public Asset Tracking e.g. where is the train now? • Personal Asset Tracking e.g. I lost my PDA, where is it now? • Location / time based offers, e.g. Free mobile phone calls while you are in location X • Location & time synchronisation: e.g., ImaHima users Ubiquitous computing: smart devices, environments and interaction

39. Location-Aware vs Spatial Aware vs Composite Spatial Aware Triggering • Awareness of a location – a point in 3D space • Awareness of a location in relation to another location • Awareness of a location in relating to its surrounding 2D space • Composite spatial awareness Ubiquitous computing: smart devices, environments and interaction

40. Location Determination Methods Several common Methods • Proximity Analysis • Triangulation • Time Difference of Arrival (TDOA), Multi-lateration • Trilateration • Received Signal Strength (RSS) Ubiquitous computing: smart devices, environments and interaction

41. Location Determination : Triangulation If distance AB, angles at A and B are known then X and Y can be determined using basic trigonometry Sin A = Y / a Sin B = Y / b Y = a * Sin A = b * Sin B Cos A = X / a X = a * Cos A = AB – b * Cos B Ubiquitous computing: smart devices, environments and interaction

42. Location determination: TDOA • Time Difference of Arrival (TDOA), Multilateration • TOA measurement of time signal sent vs. time received: distance d = time t * signal propagation speed s. • N.B. Assumes accurate clock synchronisation, sender knows time of transmission • TDOA or measurement at 2 or more receivers (or sent from 2 or more senders) • use to estimate the difference in distances between the 2. Ubiquitous computing: smart devices, environments and interaction

43. Location Determination: Trilateration • Trilateration: uses absolute measurements of time-of-arrival from three or more sites • Trilateration is a method of determining the relative positions of objects using the geometry of triangles in a similar fashion as triangulation. Ubiquitous computing: smart devices, environments and interaction

44. Location determination: Trilateration 3 Equations to determine location of point O w.r.t. known locations A,B, and C on a 2D plane RA2 =X2 +Y2 RB2 = (X-(AO+OB))2 +Y2 RC2 = (X-AO)2 +(Y-OC)2 Use substitution to get X and Y X = (RA2 - RB2 + (AO+OB)2 ) / 2 (AO+OB) Y = (RA2 - RC2 + AO2+OC2 ) / 2OC) – AOX / OC Ubiquitous computing: smart devices, environments and interaction

45. Location Determination: RSS • Received Signal Strength (RSS) Estimate the RF signal strength at a receiver • Knowing the transmission signal strength • Knowing the attenuation of the signal as a function of distance and signal transmission strength, • e.g., 1/r2 Ubiquitous computing: smart devices, environments and interaction

46. Location Determination: Range • IR / BlueTooth: ? • RFID systems: ? • WLAN: ? • GPS: ? • GSM: ? Ubiquitous computing: smart devices, environments and interaction

47. Location Determination: Uncertainty • Distance & timing measurements has some uncertainty in practice: • variable attenuation (due to moisture in air etc), • multi-path effects, • reflections, • spot interference, • knowing the time of transmission accurately etc • (see also Chapter 11) • How can we correct for this uncertainty? • We can measure signal w.r.t to multiple transmitters to correct for this variability Ubiquitous computing: smart devices, environments and interaction

48. Location Determination: Handling Inaccuracy & Uncertainty • Handling the lack of accuracy, uncertainty in the location • Accuracy requirements for some applications can be relaxed • Could use orientation or a priori knowledge of geo-attributes to help determine the location, • . • Can use hybrid systems or assisted systems that combine strengths and minimise weaknesses of several systems. Ubiquitous computing: smart devices, environments and interaction

49. Location & Other Spatial Abstractions • Location coordinate in itself is often not so useful, it is too low-level • It is the Spatial context for a location that is useful and gives it the location meaning. • E.g., • Forward-tracking: relation of the current coordination to an end coordination / future goal • e.g., • Backward tracking: relation of current location coordination to start coordination, to past routes, to past goals Ubiquitous computing: smart devices, environments and interaction

50. Location Awareness: Geographical Information System (GIS) • Need spatial services to determine the spatial context • This is a GIS service • A GIS service needs to do more answer spatial queries, it also needs to be: Ubiquitous computing: smart devices, environments and interaction