Chapter 4 Flashcards
what is A context?
A context represents the state or situation in the
environment of a system that affects that system’s (application specific) behaviour
list External environments.
physical, human, virtual
list Context Types By Application.
- Mobility context-aware
- Location aware :
- Time aware : [calendar]
what are the stages involved in the Life-cycle of Context Awareness?
- Capture Physical Context
- Capture User Context
- Context Processing
- Adapt to Context
- Manage contexts
what are the steps involved in the creation of user context?
- 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.
what are the steps involved in the creation of environment context?
- Acquisition:
- Encapsulation:
- Abstraction:
- Filtering:
- Sharing:
what is context post-processing?
It involves refining and utilizing the acquired context to make informed decisions or adaptations in a system.
what does context post-processing enable?
- Context-composition
- Context Mediation / management
- Context Adaptation
________ involves combining multiple contextual elements to create a more comprehensive and meaningful representation of the user’s situation?
Context Composition
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
what are the challenges of Context composition?
- 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
a robust context-aware system must excel in context composition, be capable of handling heterogeneous contexts, and ensure interoperability.
T
Context-aware systems may depend on & combine?
- multiple representations for a single context
- multiple representations of multiple contexts
- Multiple representations determined independently
Determination of a proposed joint context for meeting is fairly simple.
False
- it can be complex
what is the challenge of a joint context / context composition?
to harmonize or standardize annotation
so that they would be consistent used by all users.
what are the processes involved in context management?
- 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
what is the role of Directory services in discovery?
act as repositories that store information about available context sources, data stores, and users.
what are the three types of context adaptation systems?
Passive, Active, and Hybrid.
describe a Passive Context Adaptation System.
[ 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.
describe an Active context-adaptation system.
Adaptation to context performed by the UbiCom system, not human users.
In __________ does a Human user guides or corrects the automatic adaptation?
Hybrid context adaptive system
what are the two context adaptation models?
- Event-based Models [EDA]
- Reactive /intelligent Goal-based Models
describe Event-based Models.
- 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.
describe Reactive Goal-based Models.
involve the use of planned applications or user goals to narrow down the set of current contexts considered useful or relevant.
Relation of current context to goal context is fundamental.
True
outline elements related to context awareness in the context of a location-aware application.
- 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.
what are the issues when designing a context aware system?
- Context representation
- Use of Current versus Past Contexts
- Context Determination
- Static versus Dynamic CA
- Active versus Passive Context Adaptation
- Heterogeneous Contexts &Interoperability
- Context Composition
Not in the material but, describe the issues of context aware design in detail.
- Context representation : Designers may face challenges in selecting appropriate frameworks for representing context.
- Use of Current versus Past Contexts : Balancing the need for real-time responsiveness with the potential benefits of historical context.
- Context Determination : Ensuring accuracy as well as selecting appropriate sensors for context.
- Static versus Dynamic CA : Striking a balance between stability and adaptability.
- Active versus Passive Context Adaptation : Determining when to be proactive or reactive.
- Heterogeneous Contexts &Interoperability : Handling interoperability challenges in a heterogeneous environment.
- Context Composition : Managing the complexity of combining diverse contexts.
What type of data structures can be used to model contexts [ Context Representations ] ?
- 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.
Simplest type of context-aware system Uses the current context, the current state, episodic, environment.
True
simple context aware systems Operate in an environment that is not fully observed and hence need to be probabilistic.
False
- env’t is fully observed and deterministic.
accurate user context aqusition is fairly simple.
False , it can be complex
what are the 4 approaches for user context determination?
- Combine low-level sensor inputs
- Query user profile or model
- Ask users to define their own context
- Observing user interaction
________ abstracts the user by creating a profile or model that characterizes their preferences?
Querying user profile or model
List the benefits of context adaptation.
- 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
What are the challenges of Context-awareness?
- User Contexts may be incorrectly determined or predicted.
- Environment Contexts may be incorrectly determined or predicted.
- Contexts may exhibits a range of spatial-temporal characteristics
- Contexts may have alternative representations
5.Contexts may be distributed and partitioned
- Contexts may generate huge volumes of data
- Context sources often need to embedded in a low resource infrastructure
- Context use can reduce the privacy of humans
- Awareness of context shifts can distract users
given an overview of the steps involved in Spatial-Awareness?
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
List applications that trigger the use of spatial awareness.
- Navigation:
Example: “I’m lost, where is the nearest Metro station?” - Notification of Context Change:
Example: “Traffic queue ahead, change route.” - Querying Location Context:
Example: “What is the speed limit on this road?” - Emergency Service Operations:
Example: “Are flammables nearby?” - Enterprise Asset Tracking:
Example: “Where is the water supply?” - Public Asset Tracking:
Example: “Where is the train now?” - Personal Asset Tracking:
Example: “I lost my PDA, where is it now?” - Location/Time-Based Offers:
Example: “Free mobile phone calls while you are in location X.”
9 Location & Time Synchronization:
Example: “ImaHima users.”
- Personal Emergency:
Example: “Medical emergency or roadside assistance needed.”
what is Spatial awareness?
it refers to the ability of an entity, to perceive and understand its position and the positions of objects in its surroundings
Describe what is meant by “Location-Aware,” in terms of Triggers?
Definition: Awareness of a location.
Triggering Mechanism: based on a point in 3D space.
Describe what is meant by “Spatial-Aware,” in terms of Triggers?
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.
Describe what is meant by “Composite-Spatial-Aware,” in terms of Triggers?
Definition: Integration of multiple dimensions of spatial awareness.
what are the 4 classifications of awareness based on triggers?
- Location-Aware
- Spatial Aware
- Location Aware in Relation to Surrounding 2D Space
- Composite Spatial Aware
what are the methods of Location Determination?
- Proximity Analysis
- Triangulation
- Time Difference of Arrival (TDOA) [ Multi-lateration ]
- Tri-lateration
- Received Signal Strength (RSS)
________ Assumes accurate clock synchronization, i.e, sender knows time of transmission.
Time Difference of Arrival (TDOA)
How is distance calculated in Time Difference of Arrival (TDOA)?
distance (d) = time(t) * signal propagation speed(s)
How does Time Difference of Arrival (TDOA) work?
It relies on measuring the difference in the time of arrival of a signal at multiple receivers to determine the location of the source.
How does triangulation work?
By using geometric principles of triangles given 2 angles A and B
_______ uses absolute measurements of time-of- arrival from three or more sites?
Trilateration
_____ is used to Estimate the RF [ radio frequency ] signal strength at a receiver?
Recived Signal Strength RSS
what are some examples of Location Determination: Range?
- IR / BlueTooth
- RFID systems
- WLAN
- GPS
- GSM
Accuracy requirements for some applications can be relaxed
True
How can we Handle Inaccuracy & Uncertainty during Location Determination?
- 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.
Location coordinate in itself is very useful.
False.
- it is too low-level, It is the Spatial context for a location that is useful.
what is the d/ce b/n Forward-tracking and Backward-tracking?
- 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
