Benefits of integrating meta data into a context model Nicola Hönle, Uwe-Philipp Käppeler, Daniela Nicklas, Thomas Schwarz, Matthias Grossmann Nexus Center of Excellence 627: Spatial World Models for Mobile Context-Aware Applications University of Stuttgart Germany , Kauai, Hawai'i, USA

University of Stuttgart Center of Excellence CoMoRea'05 – benefits of integrating meta data into a context model2 data application meta data meta data = data about (operational) data But: distinction is application-specific! What is meta data?

University of Stuttgart Center of Excellence CoMoRea'05 – benefits of integrating meta data into a context model3 What is meta data? Some opinions... areadatameta data (relational) databases mini-world; operational data; what applications write into the tables schema information: Which tables are there? How do they look like? XMLbetween tagsthe tags HTMLweb-page content, tag in the header: author, date, keywords,... sensor datasensor value accuracy, working conditions of sensor... context modelsphysical + virtual world objects ?

University of Stuttgart Center of Excellence CoMoRea'05 – benefits of integrating meta data into a context model4 Overview Meta data in context models The Nexus Platform (short!) Integrating meta data in the Nexus Platform Benefits Data exchange, query processing Conclusion

University of Stuttgart Center of Excellence CoMoRea'05 – benefits of integrating meta data into a context model5 Physical World Context Model Context Models Applications query (filter) Update(id, value) Sensors (Modeling) Update(id, value) Application State

University of Stuttgart Center of Excellence CoMoRea'05 – benefits of integrating meta data into a context model6 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...

University of Stuttgart Center of Excellence CoMoRea'05 – benefits of integrating meta data into a context model7 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

University of Stuttgart Center of Excellence CoMoRea'05 – benefits of integrating meta data into a context model8 The Nexus Vision: Federated Context Models local context models information spaces context-aware applications data from billions of sensors WWW Digital Libraries Federation “Smart Factory” City Guide Multimodal Navigation... Virtual PostIts global context model

University of Stuttgart Center of Excellence CoMoRea'05 – benefits of integrating meta data into a context model9 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

University of Stuttgart Center of Excellence CoMoRea'05 – benefits of integrating meta data into a context model10 federated global context model AWQL/AWML Nexus Platform Architecture Context- Server Context- Server GeoDB Area Service Register Application Context- Server Context- Server Context- Server Context- Server Context- Server WWW (ext. data) WWW (ext. data) Federation Sensor  Why different context servers? See our PerCom´05 paper. local context models Application

University of Stuttgart Center of Excellence CoMoRea'05 – benefits of integrating meta data into a context model11 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)

University of Stuttgart Center of Excellence CoMoRea'05 – benefits of integrating meta data into a context model12 Which meta data do we use? temperature position object identifier value: 49N 9E value: ID1234 type value: TemperatureSensor value: 23.0 Area Service Register Context Server local context model register (AugmentedArea, ObjectTypes) meta data about data providers author: Alice gatheringTime: meta data about data objects value: 25.0 measurementTime: 08:30:00 accuracy: ±0.5 Multiple attribute instances meta data about attribute values accuracy: ±5 measurementTime: 08:00:00 accuracy: ±1

University of Stuttgart Center of Excellence CoMoRea'05 – benefits of integrating meta data into a context model13 Augmented World Modeling Language (AWML) awml nexusobject attribute value nexusobject attribute value

University of Stuttgart Center of Excellence CoMoRea'05 – benefits of integrating meta data into a context model14 AWML: data exchange with meta data ID1234 TemperatureSensor 49N 9E 5... Alice ID1234 TemperatureSensor 49N 9E 5... Alice Object meta data Attribute value with meta data

University of Stuttgart Center of Excellence CoMoRea'05 – benefits of integrating meta data into a context model15 AWML: data exchange with meta data ID :00: :30: ID :00: :30: Multiple attribute instances

University of Stuttgart Center of Excellence CoMoRea'05 – benefits of integrating meta data into a context model16 Augmented World Query Language (AWQL) awql restriction filter: include or exclude equal, less, greater and, or, not spatial: within, overlap temporal: before, after,... attribute list

University of Stuttgart Center of Excellence CoMoRea'05 – benefits of integrating meta data into a context model17 AWQL: query processing type.value TemperaturSensor pos.value SomeArea temperature.value 24.0 temperature.meta.measurementTime 08:12:00... type.value TemperaturSensor pos.value SomeArea temperature.value 24.0 temperature.meta.measurementTime 08:12:00... Step 1: provider selection (restrictions on type and position)  context server list Step 2: object selection (restrictions)  result set

University of Stuttgart Center of Excellence CoMoRea'05 – benefits of integrating meta data into a context model18 AWQL: query processing (cont.)... NOL.value temperature value meta.accuracy meta.measurementTime 08:12:00... NOL.value temperature value meta.accuracy meta.measurementTime 08:12:00 Step 3: Attribute instance selection (include)  return set

University of Stuttgart Center of Excellence CoMoRea'05 – benefits of integrating meta data into a context model19 Implementation Issues XML: optional elements, multi-elements Java: generic result set classes (multiple attribute instances,...) relational DBMS: decomposed storage model

University of Stuttgart Center of Excellence CoMoRea'05 – benefits of integrating meta data into a context model20 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?

University of Stuttgart Center of Excellence CoMoRea'05 – benefits of integrating meta data into a context model21 Mahalo! Questions?