Exploring Context
CMSC818G
• Information-Centric
Design of Systems
• Spring 2009
Christian B. Almazan
• <lastname@cs.umd.edu>
• February 2009
Simple Class Exercise
• Physically write down how you define context
• Put your name on top of the paper
• Hand in piece of paper on slide 8
Motivation
“As humans, we not
only acquire
information
through our senses,

we also feel
compelled to share
it with each other.”
Hans Christian von Baeyer [vB03]
◦ Adapted text to picture
February 2009
CMSC818G: Information-Centric Design of Systems
Topic: Exploring Context
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Goals

Examine basic concepts concerning context
◦
◦
◦
◦

Defining context and context-aware
Role of context in building systems
Expose to issues while designing a system
Look at things from a million feet in the sky
Bridge Information Dynamics
◦ Fuse with other trains of thought
◦ Primarily focused on the context aspect
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Topic: Exploring Context
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Caveats

You will/may not agree with everything said
◦ Make your own judgments about various topics
◦ Form your definition of context and context-aware

We will not focus on enabling technologies
◦ Plenty of mechanisms that involve context
◦ Focus on choosing the best fit mechanism

More raised issues than discussed solutions
February 2009
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Topic: Exploring Context
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Technology Concerning Context

Ideas to think about
◦
◦
◦
◦
◦
Sensing Mechanisms for capturing context
Modeling and Storing context
Inferring context from context
Exchanging context between entities
Using context in decision making
February 2009
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Topic: Exploring Context
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What do we mean by context?
Defining Context
Context
• ???
Context-Aware
• ???
February 2009
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Topic: Exploring Context
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Conundrum for Defining Context

Define context then develop the system?
◦ System adheres to the definition of context

Develop the system then define context?
◦ Definition highly dependent on the system

Hybrid development and defining?
◦ Iterative and agile software engineering concepts
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Topic: Exploring Context
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Not Ready to Define Yet

Already have ideas in your perceived reality
◦ Life experiences will influence your definition
◦ Information Dynamics defined context

We will come back to definitions later

In the meantime, if you did not do it already:
◦ Write down your definition of context
◦ We will ask you to do it again later
February 2009
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Topic: Exploring Context
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The Two Core Aspects of Context
Context
Time
Location

Relationship w/Respect to
Examples
Absolute
an oracle
Unix Epoch
Relative
another entity
Causal Relationship
Absolute
an oracle
GPS/Earth
Relative
another entity
Proximity
Two of the most studied aspects of context
◦ Computer Science, Philosophy, Mathematics, ...

Everything has these two pieces of context
February 2009
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Topic: Exploring Context
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How do living and artificial beings acquire information?
Physiological and
Computer Perception
“As humans, we
not only acquire
information
through our senses,
February 2009
...
CMSC818G: Information-Centric Design of Systems
Topic: Exploring Context
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Primary Physiological Senses
Taste
Hearing
Sight

Smell
Perception
Touch
Early (if not earliest) classification of the senses [Ari91]
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Simple Analysis of the Senses
Pressure
Sight
Hearing
Taste
Smell
Touch
February 2009
Location
Sight
Hearing
Taste
Smell
Touch
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Topic: Exploring Context
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Further Analysis of the Senses
Safety Distance
Pressure
Sight
Hearing
Taste
Smell
Touch
February 2009
Location
Sight
Hearing
Taste
Smell
Touch
CMSC818G: Information-Centric Design of Systems
Topic: Exploring Context
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Input Mechanisms in Computers
Physical
Mediums
Sensors
Input
Devices
Networks
Computer
February 2009
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Topic: Exploring Context
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Simple Analysis of the Input
Heat
Input
Devices
Physical
Mediums
Sensors
Tracking
Networks
February 2009
Input
Devices
Physical
Mediums
Sensors
Networks
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Topic: Exploring Context
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Further Analysis of the Input
Command Center
Heat
Input
Devices
Physical
Mediums
Sensors
Tracking
Networks
February 2009
Input
Devices
Physical
Mediums
Sensors
Networks
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Topic: Exploring Context
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Sensing in Information Dynamics
Entity
Information
Perceived Reality
Representation
Physical World
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Topic: Exploring Context
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Interpretation with a Goal
Goal
Evaluation of Interpretations
Interpreting the Perception
Perceiving the State of the World
The World

Stages of Interpretation [Nor02]
◦ We will see expanded model later
February 2009
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Topic: Exploring Context
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The Location Stack
Intentions
Activities
Contextual Fusion
Non-Context
Layers
Arrangements
Fusion
Measurements
Sensors

Layered model for multiple location sources [HBB02]
◦ Similar to the OSI model
February 2009
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Topic: Exploring Context
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Interpretation with Verification
The World
Our Interpretation
Where Our Interpretations
Come From
1. Initial Perception
The World
2. Initial Classification
3. Synthesis
Context
Body of
Knowledge
4. Test
Informed
Perception

6. Test
5. Prediction
A Model of Interpretation [McC04]
◦ Primarily concerned with business document exchange
February 2009
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Topic: Exploring Context
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Importance of Interpretation
Design
Model
User’s
Model
Designer
User
System
System
Image

Mental Models [Nor02]
◦ Do we interpret messages as intended?
February 2009
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Topic: Exploring Context
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Mars Climate Orbiter
Goal
• First non-Earth observation satellite
• Weather
• Climate
• Water
• Carbon Dioxide
Result
• Entered atmosphere of Mars
• Physical structure could not survive atmosphere
• Pressure
• Friction

http://en.wikipedia.org/wiki/Mars_Climate_Orbiter
◦ Downloaded February 5, 2009 (Mentioned in [McC04])
February 2009
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Missing Context

Rotation Jet Miscalculation (Standards)
◦ NASA’s de facto standard: Metric Units
◦ Hardware: Jet Propulsion Laboratory
 Metric Units (Newton-seconds)
◦ Software: Lockheed Martin Astronautics
 Imperial Units (pound-seconds)

Data from [Obe99]
◦ What could have been done to prevent this?
February 2009
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Topic: Exploring Context
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Accounting for Context

Calculations
◦ Off by a factor of 4.45
◦ Not an order of magnitude

System checks
Sensor checks
Take other factors into account (i.e. path)

Calculations from [Obe99]


◦ We will come back to a similar example later
February 2009
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Topic: Exploring Context
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Understanding Scales

On a scale of 1 to 10,
◦ …how much pain do you feel?
◦ …how do you rate this essay/movie/book?
◦ …how fast/cool is this car?

Questions to ask about these scales:
◦
◦
◦
◦
How did the person assign the value?
Is the scale absolute or relative to other values?
Can the person’s value be trusted?
What other context relates to the value?
February 2009
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Topic: Exploring Context
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How does effective communication take place?
Effects of Context on
Communication
...
February 2009
we also feel
compelled to share
it with each other.”
CMSC818G: Information-Centric Design of Systems
Topic: Exploring Context
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Chinese Whispers, or Telephone
Alice
Student A
Student B
• Message
• Message
• Message
Bob
Student D
Student C
• Message
• Message
• Message

Example from [vB03], though he did not invent it
◦ Communicate Message from Alice to Bob
February 2009
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Typical Result of Playing Telephone
Alice
Student A
Student B
• Message
• Message’
• Message’’
Bob
Student D
Student C
• Message’’’’’
• Message’’’’
• Message’’’

Alice’s original message never made it to Bob
◦ Why did the message become garbled?
February 2009
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Topic: Exploring Context
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Information Theory Explanation
Entity A
Information
Source
Message
Transmitter
Signal
Physical World
Noise
Source
Entity B
Destination

Message
Receiver
Received Signal
Altered from [Sha48], did not have boundaries
◦ Each student represents a noise source
February 2009
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Topic: Exploring Context
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Technical Information
“Frequently the messages have meaning;
that is they refer to or are correlated
according to some system with certain
physical or conceptual entities.
These semantic aspects of communication
are irrelevant to the engineering problem.”

Claude E. Shannon [Sha48]
◦ Does not account for why noise events occur
February 2009
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Topic: Exploring Context
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Information Dynamics Explanation
Entity A
Entity B
Information
Information
Perceived Reality
Perceived Reality
Representation
Technical Information
Representation
Physical World

Each entity goes through this process
◦ Differences in context and culture change the message
February 2009
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Topic: Exploring Context
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Chinese Characters

Scenario attributed to Jan Kåhre
◦ Believes Shannon information represents one of
many ways to measure information content

Englishman picks up Chinese newspaper
◦ Does not understand any of the characters
 Information content equals zero
◦ Person who understands translates to the person
 Information content much greater

Example from [vB03]
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Information Content
Technical Information
• Concerned about accurate message transfer
• Quantity of information per bit transmitted
• Measured information as entropy
Everyday Information
• Quality of accurately transferred information
• Translations can semantically alter a message
• Can/How should we measure this information?
February 2009
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Understanding Results

What context do we need to know to
reproduce results from papers?
◦ Do we believe the results given?
◦ Do the results convince us of the arguments?

Issues to consider:
◦ Listed specifications for the tests
◦ Granularity of the results
◦ Intangibles not listed in the paper:
 Time of Day, Location, Temperature, Altitude, …
February 2009
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Topic: Exploring Context
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How do we maintain continuous goals?
Maintaining Goals with
Context
Goal
Activity
February 2009
Context
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Topic: Exploring Context
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Goal: Automotive Cruise Control
Reach
Desired
Speed
Engage
Cruise
Control
February 2009
Automobile
Maintains
Speed
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Topic: Exploring Context
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Open-Loop System
System
Input
System
System
Output
Throttle controlled by system
 Factors not included:

◦ Hills, wind, road conditions, …
February 2009
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Topic: Exploring Context
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Closed-Loop System
Measured
Error
Controller
System
Input
System
System
Output
Sensor

Basis of control theory
◦ Introduce a feedback mechanism
◦ Monitor the output of the system
◦ Adjust throttle control as necessary
February 2009
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Topic: Exploring Context
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Interpretation with a Goal
Goal
Intention to Act
Evaluation of Interpretations
Sequence of Actions
Interpreting the Perception
Execution of the Action Sequence
Perceiving the State of the World
The World

Seven Stages of Action / The Action Cycle [Nor02]
◦ Stages of Execution and Stages of Interpretation
February 2009
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Topic: Exploring Context
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Issues: Plane Autopilot


Co-pilot noticed fuel being fed to all engines
from only one fuel tank
Steering wheel learned slightly to the right
◦ Incrementally shifted, pilots did not notice
◦ Autopilot slowly autocorrected roll

Roll caused by fuel imbalance
Other sensors indicated fuel levels

From [Nor90], need accurate feedback and interaction

◦ How do you sufficiently account for different scenarios?
February 2009
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Topic: Exploring Context
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How do others define context?
Defining Context,
Revisited
Context
• ???
Context-Aware
• ???
February 2009
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Topic: Exploring Context
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Technical Information Keywords
Instruments
Trade-Off
› › Sensors
› › Resolution
› › Transducers
› › Sensitivity
Comparisons
Surprises
Primary Reference
Redundancy
Range
Frequency
› › Overloads
› › Counting
› › Saturates
› › Trigger
Noise
Time
Finite
Entropy

Information Theory-centric book [Les01]
◦ What can we learn from the lessons from that field?
February 2009
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Topic: Exploring Context
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Forces of Evidence
Important
Number of Links
Hearsay
Relative Likeliness
Sufficiency
Time
Support
Completeness
Generalizations
Eliminate
Amount
Measure
Ancillary Evidence
Background
Fundamental
Credibility
Concurrent
Derived
Rareness
Contradictory
Force

From [Schu94], essentially the value of information
◦ With respect to a certain circumstance or frame
February 2009
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Topic: Exploring Context
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Context in Documents
“…two levels of context.”
• “a document within a broader group of documents”
• “the concepts within the document in the context of
the document”
“Context can often be derived from clues,
• and once derived can be used to further disambiguate
other terms.”

[McC04]
◦ Concerned with business systems
February 2009
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Formal Context
Context
• “Context is any information that can be used to characterize
the situation of an entity.
• An entity is a person, place, or object that is considered
relevant to the interaction between a user and an application,
including the user and application themselves.”
Context-Aware
• “A system is context-aware if it uses context to provide
relevant information and/or services to the user, where
relevancy depends on the user’s tasks.”

[Dey01]
◦ Generally accepted definition in hundreds of papers.
February 2009
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Operational Context
Formal Definition
• “Context is any information that can be used to characterize the
situation of an entity [Dey01].
Operational Definition
• Elements for the description of this context information fall into five
categories: individuality, activity, location, time, and relations.
• The activity predominantly determines the relevancy of context
elements in specific situations,
• and the location and time primarily drive the creation of relations
between entities and enable the exchange of context information
among entities.”

[ZLO07] expands Dey’s formal definition
◦ Includes operational aspect of context
February 2009
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Topic: Exploring Context
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We continually redefine the meaning of context.
Context goes beyond the definitions presented.
How does context influence the way we define systems?
Can you derive my definition of context from these slides?
What Next?
Context A
Context B
Context C
Context D
Context E
Context F
Context …
February 2009
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References
[Ari91]
[Nor02]
•Aristotle. De Anima. Prometheus Books, 1991.
[Dey01]
•Anind K. Dey. Understanding and Using Context. Personal
and Ubiquitous Computing, 5(1):4-7, February 2001.
[HBB02]
•Jeffrey Hightower, B arry Brumitt, Gaetano Borriello. The
Location Stack: A Layered Model for Location in
Ubiquitous Computing. Proceedings of the Fourth IEEE
Workshop on Mobile Computing Systems and Applications, 4,
22-28, August, 2002.
[Les01]
•James Christopher George Lesurf. Information and
Measurement. 2nd Edition, Taylor & Francis, October, 2001.
•Donald A. Norman. The Design of Everyday Things. Basic
Books, 2002.
[Obe99]
•James Oberg. Why the Mars Probe [Accident
Investigation], IEEE Spectrum, 36(12), 34-39, December,
1999.
[Schu94]
•David A. Schum. The Evidential Foundations of Probabilistic
Reasoning. Northwestern University Press, 1994.
[Sha48]
•Claude E. Shannon. A Mathematical Theory of
Communication. Bell System Technical Journal, 27:379-423,
623-656, July and October 1948.
[vB03]
[McC04]
•Dave McComb. Semantics in Business Systems. Morgan
Kaufmann, 2004.
•Hans Christian von Baeyer. Information: The New Language
of Science. Harvard University Press, 2003.
[ZLO07]
[Nor90]
•Donald A. Norman. The ‘Problem’ with Automation:
Inappropriate Feedback and Interaction, not ‘OverAutomation’. Philosophical Transactions of the Royal Society of
London. Series B, 327(1241), 585-593, April, 1990.
February 2009
•Andreas Zimmermann, Andreas Lorenz, and Reinhard
Oppermann. An Operational Definition of Context.
Lecture Notes in Computer Science, 4635/2007:558-571,
August 2007.
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Topic: Exploring Context
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