2004-09-07 Johnson Carmichael Kay Kummerfeld Hexel 1

Context Evidence and Location Authority

the disciplined managementof sensor data

into context models Chris Johnson (Australian National Univ)

David Carmichael, Judy Kay,Bob Kummerfeld (Univ of Sydney)

René Hexel (Griffith Univ)Smart Internet Technology

Cooperative Research CentreAustralia

2004-09-07 Johnson Carmichael Kay Kummerfeld Hexel 2

Context evidence & location authority

Key problems: • digest high data rate raw sensor data to

manageable input for smart applications• capture and reuse models, software and

system designs and components for further applications

2004-09-07 Johnson Carmichael Kay Kummerfeld Hexel 3

Context Service Layers are not hard-bordered

• Sensor aggregation, context, and rich context are seen as a continuum

• Context layers and smart applications have access to the IE Repository

• Repository contains models and also numbers of evidence accumulators

• Accretion+resolution:smarter sensors apply resolution procedures to one or more sets of accumulated evidence, on request

2004-09-07 Johnson Carmichael Kay Kummerfeld Hexel 4

Location modelling:focus and fusion

• focus:“location” is too big to model in all its aspects that we know about

but• fusion/reuse:

location models are expensive,we need to be able to combine existing models for new apps

2004-09-07 Johnson Carmichael Kay Kummerfeld Hexel 5

Articulated location models

• a location authority is a common base model for many applications:– a coordinate system, or naming, or landmarks– basic location data mapping relations

e.g. room/zone names, contains relation, sensor-location map

– maintenance procedures to continue models’ correspondence with changing reality

• location context services are differentiated for applications– e.g. where am I? where is person F?

what printer devices are near location P?

2004-09-07 Johnson Carmichael Kay Kummerfeld Hexel 6

Reusing models

Effective reuse of implemented context-awareness models needs

• more than a software library• common software systems architecture:

layering discipline• management of designed use of similar

components across layer boundaries– software components: support layers and

prototypes– system design notations

2004-09-07 Johnson Carmichael Kay Kummerfeld Hexel 7

2004-09-07 Johnson Carmichael Kay Kummerfeld Hexel 8

Context evidence: summary

Reuse sensors and components:resolve evidence diffferently for different applications

Design diagrams help to manage complexity of constructing with varying evidence streams

2004-09-07 Johnson Carmichael Kay Kummerfeld Hexel 9

• (last slide)

2004-09-07 Johnson Carmichael Kay Kummerfeld Hexel 10

Discipline and reuse

• revealing the design exposes system quality issues to scrutiny:– e.g. trust and privacy of the user models and the

sensor data flows• articulating the location authority/context

service allows differentiation between applications, while reusing common models

• focussed design notations encourage reuse through understanding and design review scrutiny

2004-09-07 Johnson Carmichael Kay Kummerfeld Hexel 11

Reuse in development of IE systems

• reuse of sensors, smart environment agents, information models,location authority models for environment (and authority’s contents and maintenance)

• specialisation to application functional and quality needs such asscale of distribution, specific location context information services, user privacy/trust.

Architectures and design methods, not just libraries.

2004-09-07 Johnson Carmichael Kay Kummerfeld Hexel 12

Identity and User Profiles

• The IER and user profile/model database overlap considerably: eg location is an attribute of a person– should we merge them? use the same

access method/API?• Identity:

– more than session authentication and single signon

– authentication + user profile/model

2004-09-07 Johnson Carmichael Kay Kummerfeld Hexel 13

Context producers and consumers

• Context producer: – A simple sensor– A complex rich context generator

• Context consumer:– A program that uses context information in

its operation– Consumers can also be producers: rich

context

2004-09-07 Johnson Carmichael Kay Kummerfeld Hexel 14

IE Usage Scenario(technical, not user level scenario)

• Sensors find a local IE repository server using DNS SRV records (several servers may live in a cloud to share load)

• A sensor detects a device and determines its unique ID (MAC address etc)

• The sensor notifies its local IER of the event• The IER uses the URN->URI resolution to

find the home IER for the device and sends an update to the home IER

• Programs (context, SPA etc) that have registered for notifications when the device is detected will be notified

2004-09-07 Johnson Carmichael Kay Kummerfeld Hexel 15

(5) Sensors and messaging

• Sensors are just above the level of dumb sensors – they are connected to the net and can use standard protocols

• IE repositories communicate– with sensors using logical multicast– with other IE repositories using peer-to-

peer services

2004-09-07 Johnson Carmichael Kay Kummerfeld Hexel 16

(6) Intelligent Environment Repository

• the Repository is in essence a distributed structured object database

• access to objects is via views• views provide mechanisms for privacy• views allow personas to be defined as

models over identity

2004-09-07 Johnson Carmichael Kay Kummerfeld Hexel 17

smart applications

SEA

context context

sensor aggregationdevice abstraction

devices

Usermodel

Intelligent EnvRepository

Context Service Layers

sensors

smart environmentagents