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Copyright 2008 by CEBT Problems in Context-Aware Computing (cont’d) Privacy Issues in Accessing User Information People are worried about how computer systems use and share their personal information Agents often collect and share user information Agents also share user information Lack of Reusable Context-Aware Mechanisms Many of existing context-aware systems are difficult and costly to build Because existing systems are tightly coupled with agent implementations, modifying the system often requires modifying the implementation of the agents. – Growing the number of agents could cause difficulties IDS Lab. Seminar - 3Center for E-Business Technology
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Semantic Web inSemantic Web inContext Broker ArchitectureContext Broker Architecture
Presented by Harry Chen, Tim Finin, Anupan JoshiAt PerCom ‘04
Summarized by Sungchan Park2008-11-17
Copyright 2008 by CEBT
Problems in Context-Aware Problems in Context-Aware ComputingComputing Limited Resources in Mobile Devices
Battery Power Constraints Information Storage Constraint Computing Power Constraint Communication Constraint
– Agents may be lack of sufficient knowledge to communicate with context sources in the environment e.g. knowing which sensor can provide what information and how to
communicate– Context sources may dynamically join and leave the
environment without notifying the agents
IDS Lab. Seminar - 2Center for E-Business Technology
Copyright 2008 by CEBT
Problems in Context-Aware Computing Problems in Context-Aware Computing (cont’d)(cont’d) Privacy Issues in Accessing User Information
People are worried about how computer systems use and share their personal information
Agents often collect and share user information Agents also share user information
Lack of Reusable Context-Aware Mechanisms Many of existing context-aware systems are difficult and costly to
build Because existing systems are tightly coupled with agent
implementations, modifying the system often requires modifying the implementation of the agents.– Growing the number of agents could cause difficulties
IDS Lab. Seminar - 3Center for E-Business Technology
Copyright 2008 by CEBT
BackgroundBackground Aspects of Context-Aware Computing
Enhancing User Interfaces Guiding the Adaptation of System Behavior Enabling Smart Space Applications
How Do Applications Acquire Contexts? Contexts are acquired by directly accessing low-level
context sensors Contexts are acquired from some kind of middle-ware
infrastructures that in turn interact with low-level context sensors
Contexts are acquired from servers that maintain situational knowledge about the environment
IDS Lab. Seminar - 4Center for E-Business Technology
Copyright 2008 by CEBT
Proposed Solution: Context Broker Proposed Solution: Context Broker ArchitectureArchitecture The author proposes to develop a broker-centric agent architecture (i.e.
COBRA) to provide runtime supports for context-aware systems in an Intelligent Meeting Rom environment
The core of the COBRA architecture: Domain Context Broker is responsible for Maintaining the context model of the domain, which includes domain
contexts from the past and at the present Resolving inconsistencies and ambiguities of the domain contexts through
information fusion Establishing privacy policies with users before sharing their personal
information Providing knowledge sharing service for context-aware agents through
agent communications
IDS Lab. Seminar - 5Center for E-Business Technology
Copyright 2008 by CEBT
Context-Aware Computing Meets Semantic Context-Aware Computing Meets Semantic WebWeb Semantic Web & Context-Aware System
Semantic Web standards will enhance the communication and information sharing
Semantic Web will become a major source of information for determining the context of users and thie associated daily activities– E.g. When a person enters a room, his location information (his
presence in the room) is automatically updated in his personal web site. Immediately, context-aware agents in both remote and local environment can acquire the presence information about the person through the Web without needing any sensing or reasoning.
IDS Lab. Seminar - 6Center for E-Business Technology
Copyright 2008 by CEBT
COBRA ArchitectureCOBRA Architecture Objectives
Acquiring context from heterogeneous sources– From sensors, Web, user
profiles, behavior pattern Maintaining consistent
contextual knowledge Enabling knowledge sharing
among agents Protecting the privacy of
users Domain Context Broker
Context sharing Protecting privacy
IDS Lab. Seminar - 7Center for E-Business Technology
Copyright 2008 by CEBT
The Design of Domain Context BrokerThe Design of Domain Context Broker
IDS Lab. Seminar - 8Center for E-Business Technology
Copyright 2008 by CEBT
Knowledge BaseKnowledge Base Domain Ontology
Context Model : fundamental concepts for representing contexts Information Source Model : sensors, user devices, web services, … Agent Profile Model : types or services that an agent offers, the
reason for acquiring certain contexts etc. Information Privacy Model
Domain Heuristics Help the broker to resolve knowledge inconsistency caused by
imperfect sensing Help the broker to build and maintain a shared model of context
User Privacy Policies What information can or can’t be shared, etc
IDS Lab. Seminar - 9Center for E-Business Technology
Copyright 2008 by CEBT
Inference EngineInference Engine Ontology Reasoning Module
deduce facts that can be concluded from the knowledge in the Knowledge Base in conjunction with the models that are defined in the Domain Ontology
Context Reasoning Module Reasoning about situational conditions of an entities
Knowledge Maintenance Module Check logical implication
– “If A is true, then B must be true”– “B is not true”– “A is true”– “B is true”– Inconsistent!
Apply domain heuristics– “No one person can be in two different rooms at the same time”– “Bob is currently attending a meeting in RM 201”– “Bob is currently typing a paper on his computer in RM 102”– Inconsistent!
IDS Lab. Seminar - 10Center for E-Business Technology
Copyright 2008 by CEBT
Broker BehaviorBroker Behavior Privacy Policy Negotiation
IDS Lab. Seminar - 11Center for E-Business Technology
Copyright 2008 by CEBT
Use Case: An EasyMeeting ScenarioUse Case: An EasyMeeting Scenario
Alice enters a conference room
The broker detects Alice’s presence
B
Policy says, “can share with any agents in the room”
A
B
The broker buildsthe context model
Web
Alice “beams” her policy to the broker
B
Policy says, “inform my personal agent of my location”
AB .. isLocatedIn ..
Copyright 2008 by CEBT
Use Case: An EasyMeeting Scenario Use Case: An EasyMeeting Scenario (cont’d)(cont’d)
Her agent informs the broker of her
role and intentions+
The broker tells herlocation to her agent
A
The projector agent wants to help Alice
The projector agentasks slide show info.
B
The projector agent sets up the slides
The broker informsthe subscribed agents
B
Copyright 2008 by CEBT
A Bird’s Eye View of CoBrAA Bird’s Eye View of CoBrA