Benefits of integrating meta data into a context model Nicola Hönle, Uwe-Philipp Käppeler, Daniela Nicklas, Thomas Schwarz, Matthias Grossmann Nexus Center

Benefits of integrating meta data into a context model

Nicola Hönle, Uwe-Philipp Käppeler, Daniela Nicklas, Thomas Schwarz,

Matthias Grossmann

NexusCenter of Excellence 627:Spatial World Models for Mobile Context-Aware Applications

University of StuttgartGermany

12.3.2005, Kauai, Hawai'i, USA

University of StuttgartCenter of Excellence 627

http://www.nexus.uni-stuttgart.de

2CoMoRea'05 – benefits of integrating meta data into a context model

data

applicationapplication

metadata

meta data = data about (operational) data

But: distinction is application-specific!

What is meta data?




What is meta data? Some opinions ...

area data meta data

(relational) databases

mini-world; operational data; what applications write into the tables

schema information: Which tables are there? How do they look like?

XML between tags the tags

HTML web-page content, <body> <meta> tag in the header: author, date, keywords, ...

sensor data sensor value accuracy, working conditions of sensor

... ... ...

context models physical + virtual world objects ?




Overview

Meta data in context models

The Nexus Platform (short!)

Integrating meta data in the Nexus Platform Benefits

Data exchange, query processing

Conclusion




PhysicalWorld

ContextModel

Context Models

Applications

query (filter)

Update(id, value)

Sen

sors

(Mo

delin

g)

Update(id, value)

Ap

pli

cati

on

Sta

te




Meta data in context models

Operational data: context information Meta data:

data to instances of data (not to the schema) characteristics of data circumstances of data gathering

Types (not disjoint): system generated technical restrictions technically measurable authorship, data source cost ...




Advantages

Hints about the data quality reliability, precision, consistency, age, ...

Sensor fusion and data cleansing on the fly calculation

tailored to application needs

Increases flexibility integration of context models

different application types




The Nexus Vision: Federated Context Models

localcontext models

information spaces

context-awareapplications

data from

billions ofsensors

WWWDigital Libraries

Federation

“Smart Factory”

City Guide

MultimodalNavigation

...

...

VirtualPostIts

globalcontext model




The Nexus Platform

Supports various kinds of context aware applications

Object-based data model (objects and attributes)

Local context models are stored on context servers

Context servers support a given interface Augmented World Query Language (AWQL):

simple spatial object selection and filtering

Augmented World Modeling Language (AWML) serialization of context data objects




federated globalcontext model

AWQL/AWML

Nexus Platform Architecture

Context-Server

Context-ServerGeoDB

AreaServiceRegister

ApplicationApplication

Context-Server

Context-Server

Context-Server

Context-Server

Context-Server

WWW(ext. data)

WWW(ext. data)

Federation

SensorSensor

Sensor

Why different context servers? See our PerCom´05 paper.

localcontextmodels

Application




Benefits of integrating meta data

Finding resources: meta data about local context models (Area Service Register)

Better data selection: better specifying kinds of context data (Application, Federation)

Trust and data quality: optimize results, favor certain data providers (Application, Federation)

Sensor fusion: higher level sensor fusion across several data providers (Context

Servers, Federation)

Implicit usage in data processing: application profiles simplify application queries (Federation)




Which meta data do we use?

temperature

position

objectidentifier

value: 49N 9E

value: ID1234

type value: TemperatureSensor

value: 23.0

AreaServiceRegister

ContextServer

local context model

register (AugmentedArea, ObjectTypes)

meta data about

data providers

author: AlicegatheringTime: 2004-08-08

meta data about

data objects

value: 25.0measurementTime: 08:30:00accuracy: ±0.5

Multipleattribute

instances

meta data about

attribute values

accuracy: ±5

measurementTime: 08:00:00accuracy: ±1




Augmented World Modeling Language (AWML)

awmlawml

nexusobject

nexusobject

nexusobject

attribute value

nexusobject

attribute value




AWML: data exchange with meta data

<awml> <nexusobject>

<NOL> <value> ID1234 </value> </NOL> <type> <value> TemperatureSensor </value> </type><position>

<value> 49N 9E </value><meta> <accuracy> 5 </accuracy> </meta>

</position>...<meta>

<author> Alice </author><gatheringTime> 2004-08-08 </gatheringTime>

</meta></nexusobject><nexusobject>

...</nexusobject>

</awml>


<NOL> <value> ID1234 </value> </NOL> <type> <value> TemperatureSensor </value> </type><position>

<value> 49N 9E </value><meta> <accuracy> 5 </accuracy> </meta>

</position>...<meta>

<author> Alice </author><gatheringTime> 2004-08-08 </gatheringTime>

</meta></nexusobject><nexusobject>

...</nexusobject>

</awml>

Objectmeta data

Attribute valuewith meta data




AWML: data exchange with meta data


<NOL> <value> ID1234 </value> </NOL> ...<temperature>

<value> 23.0 </value><meta>

<measurementTime> 08:00:00 </measurementTime><accuracy> 1 </accuracy>

</meta></temperature><temperature>


<measurementTime> 08:30:00 </measurementTime><accuracy> 0.5 </accuracy>

</meta></temperature>...

</nexusobject>...

</awml>


<NOL> <value> ID1234 </value> </NOL> ...<temperature>


<measurementTime> 08:00:00 </measurementTime><accuracy> 1 </accuracy>

</meta></temperature><temperature>


<measurementTime> 08:30:00 </measurementTime><accuracy> 0.5 </accuracy>

</meta></temperature>...

</nexusobject>...

</awml>

Multipleattribute

instances




Augmented World Query Language (AWQL)

awqlawql

restriction

filter: include or exclude

equal, less, greaterand, or, notspatial: within, overlaptemporal: before, after, ...

attribute list




AWQL: query processing

<awql><restriction>

<and><equal>

<target> type.value </target><referenceValue> TemperaturSensor </referenceValue>

</equal><within>

<target> pos.value </target><referenceValue> SomeArea </referenceValue>

</within><less>

<target> temperature.value </target><referenceValue> 24.0 </referenceValue>

</less><temporalAfter>

<target> temperature.meta.measurementTime </target><referenceValue> 08:12:00 </referenceValue>

</temporalAfter></and>

</restriction><include> ... </include>

<awql>

<awql><restriction>

<and><equal>

<target> type.value </target><referenceValue> TemperaturSensor </referenceValue>

</equal><within>

<target> pos.value </target><referenceValue> SomeArea </referenceValue>

</within><less>

<target> temperature.value </target><referenceValue> 24.0 </referenceValue>

</less><temporalAfter>

<target> temperature.meta.measurementTime </target><referenceValue> 08:12:00 </referenceValue>

</temporalAfter></and>

</restriction><include> ... </include>

<awql>

Step 1:provider selection(restrictions on

type and position) context server list

Step 2:object selection

(restrictions) result set




AWQL: query processing (cont.)

<awql><restriction> ... </restriction><include>

<target> NOL.value </target></include><include>

<target> temperature </target><include>

<target> value </target><target> meta.accuracy </target>

</include><restriction>

<temporalAfter><target> meta.measurementTime </target><referenceValue> 08:12:00 </referenceValue>

</temporalAfter></restriction>

</include> </awql>

<awql><restriction> ... </restriction><include>

<target> NOL.value </target></include><include>

<target> temperature </target><include>

<target> value </target><target> meta.accuracy </target>

</include><restriction>

<temporalAfter><target> meta.measurementTime </target><referenceValue> 08:12:00 </referenceValue>

</temporalAfter></restriction>

</include> </awql>

Step 3:Attribute instance selection (include)

return set




Implementation Issues

XML: optional elements, multi-elements

Java: generic result set classes (multiple attribute instances, ...)

relational DBMS: decomposed storage model




Conclusion

Extension of data model (AWM), serialization (AWQL) and query language (AWQL) to cope with meta data

Current usage: selection of data sources (providers) selection of objects

Future work: further usage of meta data for sensor fusion algorithms selection of providers based on trust metrics assessment of data quality application profiles

Important question: how trustworthy are the meta data?




Mahalo!

Questions?

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Benefits of integrating meta data into a context model Nicola Hönle, Uwe-Philipp Käppeler, Daniela Nicklas, Thomas Schwarz, Matthias Grossmann Nexus Center