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Context Fabric: Infrastructure Support for Context-Aware Systems
Jason I. HongQualifying Exam Proposal
Mar 20 2001 2
Why Context-Awareness?
Context TypesExisting Examples Human Concern
Room ActivitySmoke Alarm Safety
Room ActivityAuto Lights On / Off Convenience
Object IdentityBarcode Scanners Efficiency
Personal Identity & Time
File Systems Finding Info
TimeCalendar Reminders Memory
Mar 20 2001 3
Technology Trends
• Sensors GPS, Active Badges, Active Bats Smart Dust Cameras and microphones
• Recognition algorithms MSR Radar location from 802.11 Smart Floor footstep force (Orr & Abowd 2000)
• Wireless technologies Bluetooth, 802.11, cell phone
Mar 20 2001 4
Existing Examples
Why Context-Awareness?
Context Types Potential Examples Human Concern
Activity Safety
Activity Convenience
Identity Efficiency
Identity & Time Finding Info
Time Memory
Identity
Time
Location
Proximity
Activity
History
…
Smoke Alarm
Auto Lights On / Off
Barcode Scanners
File Systems
Calendar Reminders
Health Alert
Auto Cell Phone Off In Meetings
Service FleetDispatching
Tag Photos
Proximal Reminders
Mar 20 2001 5
A New Class of Context-Aware Apps
Active Badge(Olivetti)
ParcTabs(Xerox PARC)
Cyberguide(Abowd et al)
Mar 20 2001 6
Problems with State of the Art
• Coordinating all the context Will have many distributed, heterogeneous
sensors, services, and devices out there Won't be designed a priori for interoperability
• Building robust context-aware apps Dynamically changing computing environment Sensors, services, and devices will vary in
capability and availability
• Developers are forced to devote a lot of time and energy to non-application issues
Mar 20 2001 7
Proposed Meta-Solution
• Shift burden of context-awareness from individual devices onto infrastructure Discovering, Acquiring, Transforming, Refining,
Routing, and Reacting to Context
• Provide services that can be easily deployed everywhere and used by any device Have simple, uniform system interfaces Any device with a network connection can
discover and use these services
• Abstract out messy details of sensors and services
Mar 20 2001 8
Thesis Statement
A set of core infrastructure services coupled with a specification language for stating context needs will reduce the effort in developing robust context-aware applications.
Mar 20 2001 9
Sensor Management Service
Services
Proposed Solution
ContextEvent
Service
ContextQuery
Service
Automatic Path Creation
AppApplication
Layer
ContextLayer
Logical SensorLayer
Physical SensorLayer
ContextSpecification
Language
Agents
Device Agents
User Agents
Mar 20 2001 10
Research Contributions
• A way of explicitly specifying context needs independently of specific sensors and services (+ ontology for doing it)
• Automatically assembling a dataflow from heterogeneous sensors and services at run time to satisfy context needs
• Seeing how far queries, events, and data flow processing can go for context
Mar 20 2001 11
High-Level Plan (Mir Space Station View)
• Design Context Specification Language• Design, implement, and deploy core
context services• Evaluate by implementing several simple-
to-medium complexity apps on top• Re-iterate design and implementation
based on what was learned
Mar 20 2001 12
Outline
Background and MotivationProblem and Proposed SolutionContext Fabric ArchitectureEvaluationRelated WorkProposed ScheduleSummary
Mar 20 2001 13
Context Specification Language
<context version=1.0 type=subscribe><requestor>
[requestor identification][requestor authentication][requestor input]
</requestor><request>
[context need]</request>
</context>
Mar 20 2001 14
Context Specification Language
• Need to express context about and relationships between People, Places, Things
• Predicates Identity (Who is…? What is…? Is with…?) Location (Near? Nearest? Distance? Path?) Activity (Is busy? Is in meeting? Current task?) Time (In past? In present? In future? On date?)
• Some of this vocabulary done by Schilit Implicitly encoded in his APIs One goal is to extend his work in spec language Another is to make it extensible for future
context types
Mar 20 2001 15
Context Specification Language
• Common parameters Max number of results wanted Return name Return data type (e.g. String, List, Table) Minimal probability of correctness desired Relevant sensor input requestor has
• Event parameters Event rate (e.g. at most 1 event per second) Event callback (e.g. RPC, socket port) Max number of events desired Granularity of change (e.g. 1 meter)
Mar 20 2001 16
Context Event ServiceContext Query Service
• Uniform abstraction for apps Pass a Context Specification to Context Event
or Context Query service Everything is handled by infrastructure
• Event and queries two sides of same coin Query is synchronous and one-time Event is asynchronous and repeating
• Bulk of work is done by Automatic Path Creation though
Mar 20 2001 17
ZIP Weather
GPS ZIP
Cell GPS
Cell ZIP
Automatic Path Creation
• A way of assembling small services into larger, more interesting ones
• Operators
• PathsZIP TheatersGPS ZIP
ZIP WeatherGPS ZIP
Mar 20 2001 18
Automatic Path Creation
Sensor Input ZIP Theaters
GPS
GPS ZIP
What are the nearby movie theaters?
Sensor Input ZIP Theaters
Cell
GPS ZIPCell GPS
Sensor Input ZIP Theaters
Cell
Context OutputCell ZIPMovie
Theaters
• Automatically assemble path based on resources• Don't have to know specific sensors and services• Easier to add new ad hoc functionality• Will need a Service Description Language
Mar 20 2001 19
• Re-implement from ParcTabs (Schilit 1995)• Device Agents
– Bridge for physical devices into infrastructure– Holds context state about devices– Centralizes context to and from device (better for
preferences and filtering)– Job is to handle all context issues that
cannot / should not be handled on device itself
• User Agents– Holds context state about people– Preferences, location info, filters, etc
Agents
Mar 20 2001 20
Context Fabric ExampleContext-Aware Tour Guide
• Mobile PDA tour guide1. Display map of local area2. Display nearby points of interest3. Bring up info on proximity4. Display location of others5. Capture history
Mar 20 2001 21
Context Fabric ExampleContext-Aware Tour Guide
Palm Pilot
ContextEvent
Service
ContextQuery
Service
GPS
Automatic Path Creation
Sensor Mgt Service
Tour GuideApp
MapDatabase
PalmPilot
CellPhone
Infrastructure
Mar 20 2001 22
Context Fabric ExampleContext-Aware Tour Guide
Palm Pilot
ContextEvent
Service
ContextQuery
Service
GPS
Automatic Path Creation
Sensor Mgt Service
Tour GuideApp
MapDatabase
1. Display map of local area1. Turn on device, local GPS registerswith Sensor Management Service
Automatic Path Creation
Service Discovery
DeviceAgent
DeviceAgent
DeviceAgent
E
Q
E
Q
E Q
PalmPilot
E
Q
CellPhone
E
Q
Mar 20 2001 23
Context Fabric ExampleContext-Aware Tour Guide
Palm Pilot
ContextEvent
Service
ContextQuery
Service
GPS
Automatic Path Creation
Sensor Mgt Service
Tour GuideApp
MapDatabase
1. Display map of local area2. Start up tour guide application
Automatic Path Creation
Service Discovery
DeviceAgent
DeviceAgent
DeviceAgent
E
Q
E
Q
E Q
PalmPilot
E
Q
CellPhone
E
Q
Mar 20 2001 24
Context Fabric ExampleContext-Aware Tour Guide
Palm Pilot
ContextEvent
Service
ContextQuery
Service
GPS
Automatic Path Creation
Sensor Mgt Service
Tour GuideApp
MapDatabase
1. Display map of local area3. Setup context query for changes in location (granularity depends on if indoors or outdoors)
Automatic Path Creation
Service Discovery
DeviceAgent
DeviceAgent
DeviceAgent
E
Q
E
Q
E Q
PalmPilot
E
Q
CellPhone
E
Q
Mar 20 2001 25
Context Fabric ExampleContext-Aware Tour Guide
Palm Pilot
ContextEvent
Service
ContextQuery
Service
GPS
Automatic Path Creation
Sensor Mgt Service
Tour GuideApp
MapDatabase
1. Display map of local area4. Receive location updates
Automatic Path Creation
Service Discovery
DeviceAgent
DeviceAgent
DeviceAgent
E
Q
E
Q
E Q
PalmPilot
E
Q
CellPhone
E
Q
Mar 20 2001 26
Context Fabric ExampleContext-Aware Tour Guide
Palm Pilot
ContextEvent
Service
ContextQuery
Service
GPS
Automatic Path Creation
Sensor Mgt Service
Tour GuideApp
MapDatabase
1. Display map of local area5. Display location updates
Automatic Path Creation
Service Discovery
DeviceAgent
DeviceAgent
DeviceAgent
E
Q
E
Q
E Q
PalmPilot
E
Q
CellPhone
E
Q
Mar 20 2001 27
Context Fabric ExampleContext-Aware Tour Guide
Palm Pilot
ContextEvent
Service
ContextQuery
Service
GPS
Automatic Path Creation
Sensor Mgt Service
Tour GuideApp
MapDatabase
2. Display nearby points of interest1. Periodically query for nearby points of interest and Cache results (e.g. restaurants, landmarks, etc)
Automatic Path Creation
Service Discovery
DeviceAgent
DeviceAgent
DeviceAgent
E
Q
E
Q
E Q
PalmPilot
E
Q
CellPhone
E
Q
Mar 20 2001 28
Context Fabric ExampleContext-Aware Tour Guide
Palm Pilot
ContextEvent
Service
ContextQuery
Service
GPS
Automatic Path Creation
Sensor Mgt Service
Tour GuideApp
MapDatabase
2. Display nearby points of interest2. Local Context Query Servicedelegates to Automatic Path Creation Service
Automatic Path Creation
Service Discovery
DeviceAgent
DeviceAgent
DeviceAgent
E
Q
E
Q
E Q
PalmPilot
E
Q
CellPhone
E
Q
Mar 20 2001 29
Context Fabric ExampleContext-Aware Tour Guide
Palm Pilot
ContextEvent
Service
ContextQuery
Service
GPS
Automatic Path Creation
Sensor Mgt Service
Tour GuideApp
MapDatabase
2. Display nearby points of interest3. Automatic Path Creation Service takes GPS info andtries to answer it locally (fails).
Automatic Path Creation
Service Discovery
DeviceAgent
DeviceAgent
DeviceAgent
E
Q
E
Q
E Q
PalmPilot
E
Q
CellPhone
E
Q
Mar 20 2001 30
Context Fabric ExampleContext-Aware Tour Guide
Palm Pilot
ContextEvent
Service
ContextQuery
Service
GPS
Automatic Path Creation
Sensor Mgt Service
Tour GuideApp
MapDatabase
2. Display nearby points of interest4. Local APC delegates to infrastructure APC
Automatic Path Creation
Service Discovery
DeviceAgent
DeviceAgent
DeviceAgent
E
Q
E
Q
E Q
PalmPilot
E
Q
CellPhone
E
Q
Mar 20 2001 31
Context Fabric ExampleContext-Aware Tour Guide
Palm Pilot
ContextEvent
Service
ContextQuery
Service
GPS
Automatic Path Creation
Sensor Mgt Service
Tour GuideApp
MapDatabase
2. Display nearby points of interest5. Infrastructure APC looksfor services that can providelocation-based points of interest info or parts of this info
Automatic Path Creation
Service Discovery
DeviceAgent
DeviceAgent
DeviceAgent
E
Q
E
Q
E Q
PalmPilot
E
Q
CellPhone
E
Q
Mar 20 2001 32
Context Fabric ExampleContext-Aware Tour Guide
Palm Pilot
ContextEvent
Service
ContextQuery
Service
GPS
Automatic Path Creation
Sensor Mgt Service
Tour GuideApp
MapDatabase
2. Display nearby points of interest6. Infrastructure APC returnsrelevant information (or "failure due to x" if it cannot)
Automatic Path Creation
Service Discovery
DeviceAgent
DeviceAgent
DeviceAgent
E
Q
E
Q
E Q
PalmPilot
E
Q
CellPhone
E
Q
Mar 20 2001 33
Context Fabric ExampleContext-Aware Tour Guide
Palm Pilot
ContextEvent
Service
ContextQuery
Service
GPS
Automatic Path Creation
Sensor Mgt Service
Tour GuideApp
MapDatabase
3. Bring up info on proximity1. Setup proximity events on points of interest. Attach notes to eventthat display information about point of interest.
Automatic Path Creation
Service Discovery
DeviceAgent
DeviceAgent
DeviceAgent
E
Q
E
Q
E Q
PalmPilot
E
Q
CellPhone
E
Q
Mar 20 2001 34
Context Fabric ExampleContext-Aware Tour Guide
Palm Pilot
ContextEvent
Service
ContextQuery
Service
GPS
Automatic Path Creation
Sensor Mgt Service
Tour GuideApp
MapDatabase
4. Display location of others1. Subscribe to location changeevents from others.
DeviceAgent
DeviceAgent
DeviceAgent
E
Q
E
Q
E Q
Automatic Path Creation
Service Discovery
PalmPilot
E
Q
CellPhone
E
Q
Mar 20 2001 35
Context Fabric ExampleContext-Aware Tour Guide
Palm Pilot
ContextEvent
Service
ContextQuery
Service
GPS
Automatic Path Creation
Sensor Mgt Service
Tour GuideApp
MapDatabase
4. Display location of others2. Can't process locally, subscription request forwarded to mirroring Device Agent.
Automatic Path Creation
Service Discovery
DeviceAgent
DeviceAgent
DeviceAgent
E
Q
E
Q
E Q
PalmPilot
E
Q
CellPhone
E
Q
Mar 20 2001 36
Context Fabric ExampleContext-Aware Tour Guide
Palm Pilot
ContextEvent
Service
ContextQuery
Service
GPS
Automatic Path Creation
Sensor Mgt Service
Tour GuideApp
MapDatabase
4. Display location of others3. Device Agent makes individualsubscription requests.
Automatic Path Creation
Service Discovery
DeviceAgent
DeviceAgent
DeviceAgent
E
Q
E
Q
E Q
PalmPilot
E
Q
CellPhone
E
Q
Mar 20 2001 37
Context Fabric ExampleContext-Aware Tour Guide
Palm Pilot
ContextEvent
Service
ContextQuery
Service
GPS
Automatic Path Creation
Sensor Mgt Service
Tour GuideApp
MapDatabase
4. Display location of others4. Individual device agents makea subscription request to theirmirroring devices.
PalmPilot
Automatic Path Creation
Service Discovery
DeviceAgent
DeviceAgent
DeviceAgent
E
Q
E
Q
E Q
E
Q
CellPhone
E
Q
Mar 20 2001 38
Context Fabric ExampleContext-Aware Tour Guide
Palm Pilot
ContextEvent
Service
ContextQuery
Service
GPS
Automatic Path Creation
Sensor Mgt Service
Tour GuideApp
MapDatabase
4. Display location of others5. Location change events are routed back to tour guide and displayed.
Automatic Path Creation
Service Discovery
DeviceAgent
DeviceAgent
DeviceAgent
E
Q
E
Q
E Q
PalmPilot
E
Q
CellPhone
E
Q
Mar 20 2001 39
Context Fabric ExampleContext-Aware Tour Guide
Palm Pilot
ContextEvent
Service
ContextQuery
Service
GPS
Automatic Path Creation
Sensor Mgt Service
Tour GuideApp
MapDatabase
5. Capture history1. Just store all interesting events locally.
DeviceAgent
DeviceAgent
DeviceAgent
E
Q
E
Q
E Q
PalmPilot
E
Q
CellPhone
E
Q
Automatic Path Creation
Service Discovery
Mar 20 2001 40
Outline
Background and MotivationProblem and Proposed SolutionContext Fabric ArchitectureEvaluationRelated WorkProposed ScheduleSummary
Mar 20 2001 41
Evaluation
• Iterative design process Work out designs, deploy, build apps, refine
• Initial evaluation apps will be existing ones Reimplement some existing context-aware apps Informally evaluate apps for robustness Informally evaluate apps for defaults (e.g.
privacy policy)
• Continued evaluation will be novel apps Focus on robustness and defaults again Also get others to build context-aware apps
Mar 20 2001 42
Related Work
• ParcTab System (Schilit 1995) Device Agents, User Agents, Active Maps Plan to re-implement these and new ones too
• Context Toolkit (Dey 2000) Widgets, Interpreters, Aggregators Much is subsumed in Automatic Path Creation
• Interactive Workspaces (Fox et al 2000) Paths path creation and blackboard architecture Self-describing and extensible events
Mar 20 2001 43
How Context Fabric Differs
• Separate what context is needed from how it is processed via Context Spec Language
• Shift processing from static to dynamic Say what you need at design-time Figure out how to get it at run-time through
Automatic Path Creation
Mar 20 2001 44
Proposed Schedule
• Phase 1 (0-8 months / PARC) Initial design and implementation of Context
Specification Language and core services Evaluate with simple context-aware apps
• Phase 2 (8-12 months) Re-iterate and incorporate what was learned Release source code Evaluate with medium complexity apps
• Phase 3 (12-18 months) Incorporate more feedback (smaller changes) Write dissertation
Mar 20 2001 45
Exit Conditions and Deliverables
• Spec for Context Specification Language Basic ontologies for context Expressive enough for majority of context apps
• Working core services Context Query, Context Event, Automatic Path
Creation, plus basic operators Service Description Language for APC operators
• Source code available for general use
Mar 20 2001 46
Summary
• Infrastructure approach to context-awareness
• Context Specification Language for stating context needs
• Context Event Service, Context Query Service as primary APIs
• Automatic Path Creation for processing• Evaluation focused on defaults and
robustness
Mar 20 2001 47
A New Cal Record!!
• Only one day to schedule quals…
• …through email…
• …with a professor at Stanford even!
Mar 20 2001 48
Extra Slides
Mar 20 2001 49
What is Context?
• Situated Action (Suchman) Responsiveness, improvisation to situation Actions are moment-by-moment, highly fluid on
situation
• Activity Theory (Nardi) Subject, Object[ive], Operations, Artifacts, Env Activity defines context but it changes as list
above changes Context depends on sensing and inferring, but
difficult to know people or goals
Mar 20 2001 50
What is Context?
• Provides fair criticisms on existing context-aware apps Response: Focus on the more routine and
predictable actions Response: Focus on simple first-order approx Examples: Smoke alarms, Calendar reminders
Response: Is occasionally wrong, but won't get better unless we do more research here
Response: Infrastructure enables more research in this area
Mar 20 2001 51
What is Context?
• Merging of virtual with physical and social Mostly implicit input, often secondary to
task at hand
• People / Places / Things / Virtual / Time People: Location, Identity, Task, Affect Places: Activity, People, Temperature, Audio Things: Location, Identity Virtual: Services, Bandwidth Time: All of these Past, Present, and Future
Mar 20 2001 52
What is Context?
• But it's a rathole to try to define it… Workflows? (Greenberg 2001) Intent and Desire? Natural Language Processing? What isn't context?
• Instead, operationalize it Distributed, multi-device, sensor-based Fairly well-defined and computable concepts
(e.g. location and identity, but not intent or workflow)
Mar 20 2001 53
Why Context-Awareness?
• Sensors are coming• Increase channels of input / output
GraphicsSound
MouseKeyboard
Mar 20 2001 54
Why Context-Awareness?Skeptics toward the ubiquitous computing movement quickly point out that those involved in promoting Mark Weiser's initial vision are mainly interested in pushing technology…
As a reaction against this fair criticism, many researchers spend countless hours trying to dream up the "killer application" that will cause everyone to adopt ubiquitous computing technology.
I think this is the wrong goal to have in mind as a researcher for two reasons. First, we are not schooled in the practices to judge a market…
Second, my interpretation of Weiser's vision is not that there would be a single, most compelling use of ubicomp technology, but rather that the totality of the experience would cause a significant paradigm shift in the way we as humans perceive our relationship to interactive computing.
In short, Weiser argued for what I would like to call a "killer existence," in which many disparate devices would provide an array of services in ways that seamlessly complement our lifestyles.
-- Gregory Abowd, 2001
Mar 20 2001 55
Why Context-Awareness?
Sensors Computers
Context-Aware Computing
Physical World Virtual World
Mar 20 2001 56
Why Infrastructure Approach?
• Sharing of data Collaborative filtering, large data sets
• Sharing of processing power Heavy-duty processing on dedicated machines
• Sharing of sensors Sensors in the environment
• In-place evolution of services New algorithms, new features
• Supports heterogeneity Sensors, Devices, OS, Programming Langs
Mar 20 2001 57
Why Infrastructure Approach?
• Building and evaluating now can Provide more design space for interaction Let us rapidly prototype and evaluate these apps Find problems now Develop the right mechanisms Evolve the right policies
Mar 20 2001 58
Other Related Work
• Context Toolkit Widgets, Interpreters, Aggregators
• ParcTab system User agents, Device agents, Active Maps
• Interactive Workspaces Event heap, Path Creation
• MUSE Jini services, Bayesian reasoning
Mar 20 2001 59
Some Sensors
• Temperature• Pressure• Humidity• Soil makeup• Acceleration• Noise• Material stress
• Biometric• Motion• Distance• Touch• Location• Orientation• Light
Mar 20 2001 60
Related WorkContext Toolkit
• Widgets, Interpreters, Aggregators• Hardwired data flow
Face Recognition
LocationWidget
LocationWidget
In/Out Board
Smart Card Reader
ID to NameInterpreter
BuildingAggregator
Mar 20 2001 61
Related WorkParcTab System
• Will need to re-implement parts of ParcTab system Device Agents / User Agents / Active Maps
Mar 20 2001 62
Related WorkInteractive Workspaces
• Event Heap Scaling of tuple spaces will be a problem Can use how events are described
Mar 20 2001 63
Related WorkMUSE
• Sensor management issues Sensor discovery (currently via Jini) Power consumption
• Probabilistically modeling sensor data Sensor fusion (via Bayesian nets and HMMs)
Mar 20 2001 64
Rough Taxonomy ofContext-Aware Apps
• Triggers• Metadata Tagging• Reconfiguration and Streamlining• Input specification• Presentation
Mar 20 2001 65
Rough Taxonomy ofContext-Aware Apps
• Triggers On X do Y "Notify doctor and nearby ambulances if
serious health problem detected" (Citris)
"Remind me to talk to Chris about user studies next time I see him" (Proxy Lady)
• Metadata Tagging "Where was this picture taken?" "Find all notes taken while Mae was talking" Memory prosthesis (Forget-me-not)
Mar 20 2001 66
Rough Taxonomy ofContext-Aware Apps
• Reconfiguration and Streamlining Telephone forwarding and Teleport (Active Badges)
Turn off cell phone in theaters Automatically adjust brightness / volume Automatic file pre-caching (OceanStore)
Select modes in multimodal interaction Multimedia/Bandwidth adaptation (Odyssey)
Mar 20 2001 67
Rough Taxonomy ofContext-Aware Apps
• Input specification Send mail to people in building (Geocasting)
Print to nearest printer (ParcTabs)
"Find gas stations nearest me"
• Presentation Current location (Cyberguide)
Idle? (Yahoo Messenger, finger)
Currently in? (In / Out board)
Contextual info about objects (CoolTown)
Proximate selection (ParcTab)
Mar 20 2001 68
Context-Aware Mechanisms
• Events Something interesting has just happened e.g. "Larry has entered room 306"
• Queries Introspect current context state (discrete) e.g. "Where is Larry now?"
• Filters Modify events and queries based on
preferences and privacy e.g. "Only show others if in office or not"
Mar 20 2001 69
Are Queries and Events Enough?
Triggers
Metadata Tagging
Reconfiguration
Input Specification
Presentation
Query
Query for relevantcontext state
Query current context state before and while running
Query current context stateto fill in the blanks
Query current statefor more information
Event
On Event do Action
On Event do Reconfigure
On Event do Update Presentation
Mar 20 2001 70
What I Will Not Be Working On
• Building a new service infrastructure• Developing new sensors• Extremely sophisticated forms of context
Natural language processing User intention
• New algorithms for… Sensor / context fusion Machine learning Power consumption Just use algorithms that already exist!
Mar 20 2001 71
What I Will Not Be Working On
• Sophisticated preferences Enable us to explore this space more
• Comprehensive security and privacy mechanisms Will implement basic preferences, filters, and
access control One subgoal is to get the defaults right
• Rigorous user evaluations