ContextAwareness in Mobile Environments

1
Context-Awareness in Mobile Environments

• Gruia-Catalin Roman
• Mobile Computing Laboratory
• Department of Computer Science and Engineering
• 7 June 2002 (Philadelphia, PA)

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Trends in Mobile Computing

• Technology
• Miniaturization
• Wireless communication
• Java
• Society
• Ubiquitous access
• Increasing levels of mobility
• Computing and communication melting into the
  fabric of society
• Infrastructure
• Enterprises
• People

3
Physical Mobility

• Fixed network
• Nomadic computing
• Ad hoc computing

4
Research Implications

• New design constraints
• Frequent disconnection
• Unpredictable movement
• Asymmetric bandwidth
• Limited resources
• Short battery life

• Interesting opportunities
• Spatial knowledge
• Movement profile
• Increased demands
• Reasoning about behavior
• Connectivity maintenance
• Adaptation

5
Logical Mobility

• Code on demand
• Remote evaluation
• Mobile agents

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Research Trends

• Code on demand is made popular by Java
• Mobile code languages (e.g., Oblique, Facile,
  Telescript) are losing ground
• Mobile agent systems (e.g., Agent TCL) are an
  emerging new technology
• Middleware is growing in practical importance

7
Mobility Paradigms

• Continued access to remote resources
• Delegation to mobile agents
• Disconnected operation
• Ad hoc grouping of people and devices
• Mass mobility

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Ad Hoc Network Challenge

• No fixed network infrastructure
• Transient interactions
• Decoupled computing
• Open environment
• Physical and logical mobility
• Frequent disconnections
• Limited guarantees

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Sample Applications

• Highway information management
• Disaster response
• Military applications
• Contamination zone exploration
• Wireless anywhere classroom
• Cave and mine exploration
• Self-organizing office and factory
• Video games in physical spaces

10
Mobile Computing Laboratory

• Rapid development of dependable mobile
  applications over ad hoc networks
• Formal models
• precise semantics and analysis
• Coordination Models
• rapid development
• Middleware
• easy dissemination
• Algorithms
• feasible implementation
• Applications
• empirical evaluation

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Research Strategy

• Formal models
• Integrated perspective on physical and logical
  mobility
• Pragmatic use of formal thinking
• Precise semantics for coordination constructs
• Formal verification of protocols and algorithms
• Informal reasoning during the design process
• Communication
• High-level abstract coordination mechanisms
• Mobility and location sensitive protocols
• Programming
• Decoupled style of computing
• Context aware programming methods
• Middleware supported application development

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Recent Activities

• Formal models of mobility
• Mobile UNITY
• CodeWeave
• Coordination models
• GVDS Global Virtual Data Structures
• Application-specific coordination models
• Middleware for mobility
• LIME
• Coordination veneers over LIME
• LIMELite
• Algorithms and protocols for mobile computing
• Mobile applications including peer to peer
  communication on highways

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Mobile UNITY

• Program
• unit of modularity
• unit of mobility
• fully decoupled
• Mobility
• arbitrary physical and logical spaces
• reduced to assignment
• System
• programs
• small set of coordination constructs
• Proof logic
• minimal extension of UNITY

Y
X
UNITY ? unique names
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Model Evaluation
correspondentnode

• Rich set of coordination constructs expressing
  transient and transitive interactions
• Formal specification and verification of Mobile
  IP
• Formal specification and verification of mobile
  code
• Semantic basis for a new model of fine grained
  mobility (CodeWeave)
• Reactive programming support for dynamic
  reconfiguration

homeagent
foreignagent
mobilenode
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Coordination Models
service usage

• Global virtual data structures (GVDS)
• Service provision (Jini) in ad hoc networks
• Event notification in ad hoc networks
• Ad hoc code repositories
• Administrative domain structures in ad hoc

service discovery
service registration
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A Middleware for Mobility LIME
federated tuple space

• Profile
• Linda-style coordination extended to ad hoc
  settings
• Transparent data sharing based on connectivity
• Atomic and transitive engagement and
  disengagement
• Selective data sharing
• Transparent tuple migration
• Novel reactive constructs
• Distribution
• Open source
• Available on SourceForge
• Active efforts
• LIMELite
• Coordination veneers

hosttuple space
mobileagent
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Mobile Algorithms

• New algorithm design strategies for nomadic
  settings
• host as message paradigm
• FIFO communication/motion
• Message delivery
• adaptation of distributed snapshots
• Mobile tracking
• based on diffusing computations
• Termination detection
• formal derivation
• disconnected routing

mobile unit
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Applications

• Wireless chat room
• Decoupled game playing
• Commando games
• Cooperative work (puzzle)
• Technology transferFord Research, Detroit, MI
• smart intersections
• synchronized cruse control

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Context Awareness Revisited

• Context awareness is a necessity in ad hoc
  mobility
• Agility is important in highly dynamic
  environments
• Small components rely on opportunistically
  available resources while available
• Perception of context varies by task and
  situation
• Large-scale deployment of context-aware
  middleware rests with asking for exactly what is
  needed, when it is needed, and nothing more
• Transparent context management can simplify the
  programming task

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Computational Model

• Ad hoc network
• Mobile host
• Mobile agent
• Object/Data

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Agent-Centered Context

• Context is extended beyond host boundaries
• Context is separated into task-specific views
• An agent may have multiple views
• Views may change over time
• Views are defined in terms of propertiesof the
  network, hosts, agents, and objects
• Active views may exhibit built-in behaviors
  (e.g., data migration)

referenceagent
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Technical Considerations

• Presentation style
• coordination model amd semantics
• Definition
• declarative specification
• expressive power
• Computation
• context discovery and maintenance
• context evaluation infrastructure
• Delivery vehicle
• middleware framework

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Perspectives on Context

• Context-sensitive data structures
• Context-sensitive references
• Context-sensitive bindings
• Context-sensitive events

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Declarative Context Specification

• D distance to the first open EXXON gas station
  on the right
• B Internet access via a 1Mb connection within
  two hops
• P closest laser printer within 50 ft.

EXXON 9.2 mil.
lprjohn
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Infrastructure Support

• Group membership
• masking unannounced disconnection
• location based protocols
• safe distance concept
• Network abstraction
• spatiotemporal services
• strictly monotonic metrics
• bounds

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Points of Synergy

• Executable specifications
• Formal semantic analysis
• Weak semantics and formal guarantees
• Algorithm and protocol design and analysis
• Novel routing protocols
• Security mechanics
• Common middleware frameworks

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Conclusions

• Mobility challenges our way of thinking
• we explore novel uses of location information and
  more
• A solid grounding in traditional distributed
  computing is a prerequisite for success
• we leverage off past work on formal models and
  algorithms
• Complexity demands an increasing reliance on
  pragmatic application of rigorous design
  technique
• we focus on coordination models having precise
  semantics
• Sensitivity to the market place and application
  demands is more important than ever
• we emphasize application-driven empirical
  evaluation

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Thank you
cs.wustl.edu/mobilab/