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pervasive computing > Chapter 4 > Flashcards

Chapter 4 Flashcards

1
Q

what is A context?

A

A context represents the state or situation in the
environment of a system that affects that system’s (application specific) behaviour

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2
Q

list External environments.

A

physical, human, virtual

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3
Q

list Context Types By Application.

A
  • Mobility context-aware
  • Location aware :
  • Time aware : [calendar]
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4
Q

what are the stages involved in the Life-cycle of Context Awareness?

A
  • Capture Physical Context
  • Capture User Context
  • Context Processing
  • Adapt to Context
  • Manage contexts
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5
Q

what are the steps involved in the creation of user context?

A
  • 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.
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6
Q

what are the steps involved in the creation of environment context?

A
  • Acquisition:
  • Encapsulation:
  • Abstraction:
  • Filtering:
  • Sharing:
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7
Q

what is context post-processing?

A

It involves refining and utilizing the acquired context to make informed decisions or adaptations in a system.

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8
Q

what does context post-processing enable?

A
  • Context-composition
  • Context Mediation / management
  • Context Adaptation
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8
Q

________ involves combining multiple contextual elements to create a more comprehensive and meaningful representation of the user’s situation?

A

Context Composition

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8
Q

Context composition may also be driven by the need to?

A
  • Improve acquisition accuracy for the context
  • Improve filtering and adaptation of content
  • Composite contexts are in inherent an application
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8
Q

what are the challenges of Context composition?

A
  • 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
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9
Q

a robust context-aware system must excel in context composition, be capable of handling heterogeneous contexts, and ensure interoperability.

A

T

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9
Q

Context-aware systems may depend on & combine?

A
  • multiple representations for a single context
  • multiple representations of multiple contexts
  • Multiple representations determined independently
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10
Q

Determination of a proposed joint context for meeting is fairly simple.

A

False
- it can be complex

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10
Q

what is the challenge of a joint context / context composition?

A

to harmonize or standardize annotation
so that they would be consistent used by all users.

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11
Q

what are the processes involved in context management?

A
  • Discovery : involves the identification and registration of context sources, stores, and users. By using Directory services.
  • Storage : of context data into some data resource
  • Sharing : of both environmental context ( location, temperature ) and goal context ( user preferences, objectives ).
  • Access control : regulating permission of the context
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12
Q

what is the role of Directory services in discovery?

A

act as repositories that store information about available context sources, data stores, and users.

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13
Q

what are the three types of context adaptation systems?

A

Passive, Active, and Hybrid.

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14
Q

describe a Passive Context Adaptation System.

A

[ Context is presented to users without active system adaptation ]
Features:
- context is presented to users.
- Context-based tagging may be employed.
- System does not actively adapt based on the presented context.

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15
Q

describe an Active context-adaptation system.

A

Adaptation to context performed by the UbiCom system, not human users.

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16
Q

In __________ does a Human user guides or corrects the automatic adaptation?

A

Hybrid context adaptive system

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17
Q

what are the two context adaptation models?

A
  • Event-based Models [EDA]
  • Reactive /intelligent Goal-based Models
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18
Q

describe Event-based Models.

A
  • involve the connection between a context producer and a context consumer.
  • These models rely on events, which could be changes or occurrences in the environment, to trigger adaptations in the system.
19
Q

describe Reactive Goal-based Models.

A

involve the use of planned applications or user goals to narrow down the set of current contexts considered useful or relevant.

20
Q
A
20
Q

Relation of current context to goal context is fundamental.

A

True

21
Q

outline elements related to context awareness in the context of a location-aware application.

A
  • Goal Context: travel to the desired location.
    —— Example: Navigating to a specific destination or finding nearby points of interest.
  • Current Context: current location.
    ——- Example: The current geographical coordinates, environmental conditions, or user activity.
  • Context Path: Planned path from the current to destination location
    ——– Example: A log of previous locations visited or a trail of context changes.
  • Constraints: Not to deviate too far from the anticipated or planned position context.
    ——— Example: Avoiding certain areas, adhering to traffic rules, or considering user preferences.
22
Q

what are the issues when designing a context aware system?

A
  • Context representation
  • Use of Current versus Past Contexts
  • Context Determination
  • Static versus Dynamic CA
  • Active versus Passive Context Adaptation
  • Heterogeneous Contexts &Interoperability
  • Context Composition
23
Q

Not in the material but, describe the issues of context aware design in detail.

A
  1. Context representation : Designers may face challenges in selecting appropriate frameworks for representing context.
  2. Use of Current versus Past Contexts : Balancing the need for real-time responsiveness with the potential benefits of historical context.
  3. Context Determination : Ensuring accuracy as well as selecting appropriate sensors for context.
  4. Static versus Dynamic CA : Striking a balance between stability and adaptability.
  5. Active versus Passive Context Adaptation : Determining when to be proactive or reactive.
  6. Heterogeneous Contexts &Interoperability : Handling interoperability challenges in a heterogeneous environment.
  7. Context Composition : Managing the complexity of combining diverse contexts.
24
Q

What type of data structures can be used to model contexts [ Context Representations ] ?

A
  • Key-Value Pairs
  • Hierarchies / Markup Schemes, e.g., XML
  • Graphs : Context information is modeled as nodes
  • Object Oriented (o-o)
  • Logic Based: support reasoning about context
  • Strong Ontology : specifying entities, relationships, and axioms.
25
Q

Simplest type of context-aware system Uses the current context, the current state, episodic, environment.

A

True

26
Q

simple context aware systems Operate in an environment that is not fully observed and hence need to be probabilistic.

A

False
- env’t is fully observed and deterministic.

27
Q

accurate user context aqusition is fairly simple.

A

False , it can be complex

28
Q

what are the 4 approaches for user context determination?

A
  • Combine low-level sensor inputs
  • Query user profile or model
  • Ask users to define their own context
  • Observing user interaction
29
Q

________ abstracts the user by creating a profile or model that characterizes their preferences?

A

Querying user profile or model

30
Q

List the benefits of context adaptation.

A
  • Reduces information overload on users
  • Lessen cognitive load on users
  • Filter information to fit a mobile device’s display
  • Benefits for Disabled people
  • Improve Regulation &Control
31
Q

What are the challenges of Context-awareness?

A
  1. User Contexts may be incorrectly determined or predicted.
  2. Environment Contexts may be incorrectly 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

  1. Contexts may generate huge volumes of data
  2. Context sources often need to embedded in a low resource infrastructure
  3. Context use can reduce the privacy of humans
  4. Awareness of context shifts can distract users
32
Q

given an overview of the steps involved in Spatial-Awareness?

A

1 Trigger spatial-aware services
2. Sense / determine current Location
3. Determine the spatial context [ indoor/outdoor, proximity to landmarks … ]
4. Service adaptation: adapt spatial information view w.r.t. location

33
Q

List applications that trigger the use of spatial awareness.

A
  1. Navigation:
    Example: “I’m lost, where is the nearest Metro station?”
  2. Notification of Context Change:
    Example: “Traffic queue ahead, change route.”
  3. Querying Location Context:
    Example: “What is the speed limit on this road?”
  4. Emergency Service Operations:
    Example: “Are flammables nearby?”
  5. Enterprise Asset Tracking:
    Example: “Where is the water supply?”
  6. Public Asset Tracking:
    Example: “Where is the train now?”
  7. Personal Asset Tracking:
    Example: “I lost my PDA, where is it now?”
  8. Location/Time-Based Offers:
    Example: “Free mobile phone calls while you are in location X.”

9 Location & Time Synchronization:
Example: “ImaHima users.”

  1. Personal Emergency:
    Example: “Medical emergency or roadside assistance needed.”
34
Q

what is Spatial awareness?

A

it refers to the ability of an entity, to perceive and understand its position and the positions of objects in its surroundings

35
Q

Describe what is meant by “Location-Aware,” in terms of Triggers?

A

Definition: Awareness of a location.
Triggering Mechanism: based on a point in 3D space.

36
Q

Describe what is meant by “Spatial-Aware,” in terms of Triggers?

A

Definition: Awareness of a location in relation to another location.
Triggering Mechanism: based on the relationship between the current location and other points in space.

37
Q

Describe what is meant by “Composite-Spatial-Aware,” in terms of Triggers?

A

Definition: Integration of multiple dimensions of spatial awareness.

38
Q

what are the 4 classifications of awareness based on triggers?

A
  • Location-Aware
  • Spatial Aware
  • Location Aware in Relation to Surrounding 2D Space
  • Composite Spatial Aware
39
Q

what are the methods of Location Determination?

A
  • Proximity Analysis
  • Triangulation
  • Time Difference of Arrival (TDOA) [ Multi-lateration ]
  • Tri-lateration
  • Received Signal Strength (RSS)
40
Q

________ Assumes accurate clock synchronization, i.e, sender knows time of transmission.

A

Time Difference of Arrival (TDOA)

41
Q

How is distance calculated in Time Difference of Arrival (TDOA)?

A

distance (d) = time(t) * signal propagation speed(s)

42
Q

How does Time Difference of Arrival (TDOA) work?

A

It relies on measuring the difference in the time of arrival of a signal at multiple receivers to determine the location of the source.

43
Q

How does triangulation work?

A

By using geometric principles of triangles given 2 angles A and B

44
Q

_______ uses absolute measurements of time-of- arrival from three or more sites?

A

Trilateration

45
Q

_____ is used to Estimate the RF [ radio frequency ] signal strength at a receiver?

A

Recived Signal Strength RSS

46
Q

what are some examples of Location Determination: Range?

A
  • IR / BlueTooth
  • RFID systems
  • WLAN
  • GPS
  • GSM
47
Q

Accuracy requirements for some applications can be relaxed

A

True

48
Q

How can we Handle Inaccuracy & Uncertainty during Location Determination?

A
  • 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.
49
Q

Location coordinate in itself is very useful.

A

False.
- it is too low-level, It is the Spatial context for a location that is useful.

50
Q

what is the d/ce b/n Forward-tracking and Backward-tracking?

A
  • Forward-tracking: relation of the current coordination to an end coordination / future goal
  • Backward tracking: relation of current location coordination to start coordination, to past routes, to past goals

pervasive computing (3 decks)

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