1 DMS-DQS-SUPSC03-PRE-12-E © DEIMOS Space S.L., 2007 A Semantic Data Grid for Satellite Mission...

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DMS-DQS-SUPSC03-PRE-12-E © DEIMOS Space S.L., 2007

A Semantic Data Grid A Semantic Data Grid for Satellite Mission for Satellite Mission

Quality AnalysisQuality Analysis

Reuben WrightDeimos Space

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• Satellite Mission Quality Analysis• Semantic Grid development• Queries and reports• Evaluation• Questions

Table of contentsTable of contents

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• (Very) remote, programmable cameras

• Plan files converted to Telecommands and sent to Satellite

• Product data, as Telemetry, sent down from Satellite to Ground Station

• Data processed in various stages, adding geographical info, interpreting layers, etc

Earth ObservationEarth Observation

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Mission Mission Quality Quality AnalysisAnalysis

• Satellite Ground Segment consists of:– Mission Planning, Flight Operations, Acquisition Stations,

Processing Centres, Archives, Dissemination, and more...– Most interfaces are exchanging files. Mix of binary, Ascii and XML

• Currently Quality Analysis is carried out by a Monitoring Facility which receives copies of these files

• Uses a bespoke system called QUARC– Produces many reports comparing planned activity, satellite

product acquisions, processing, disseminations, etc...– However, since we are looking for problems, the system would

ideally be much more flexible• OntoGrid built a Semantic Grid to capture and access the same data

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Semantic Data GridSemantic Data Grid

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Semantic GridSemantic Grid

• Grid system, deployed over Globus toolkit• Semantically enabled - S-OGSA architecture.

– Grid entities – Knowledge entities – Semantic bindings

• Semantic Provisioning Services• Note that Semantic bindings are “first class citizens” – they

have an identity, can have metadata, can be updated • Project built semantically aware Grid Services which create,

manage and query Semantic Bindings

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AnnotationAnnotation

• Working with– Planning files (to program the satellite)– Product files (data at various processing stages)

• Onto-DSI extracts the relevant information• RDFS Grid Access Bridge provides Satellite Ontology• GridKP creates annotations (metadata) • Semantic Binding Service manages them• System manages updates/overlaps of Plan files. Possible

because the metadata is itself an object, with provenance etc• Key issue with extracting the metadata from the files is that

systems often store it in implicit forms, which we made explicit

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corresponds to:

Annotation exampleAnnotation example

• Product filename:

RA2_MW__1PNPDK20060201_120535_000000062044_00424_20518_0349.N1

<rdf:Description rdf:about="http://www.ontogrid.net/OWL/Satellite_Use_Case#44">

<rdf:type rdf:resource="http://www.ontogrid.net/OWL/Satellite_Use_Case#Product_File"/>

<suc:product_file_name>"RA2_MW__1PNPDK20060201_120535_000000062044_00424_20518_0349.N1"</suc:product_file_name>

<suc:sensing_start>192149893</suc:sensing_start><suc:sensing_stop>192155072</suc:sensing_stop><suc:plan_event_id>RA2_MW</suc:plan_event_id><suc:executed_by_instrument

rdf:resource="http://www.ontogrid.net/OWL/Satellite_Use_Case#2"/>

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OWL in SpaceOWL in Space

• Section of Ontology for Space Systems and Earth Observations

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Data StoreData Store

• RDF storage in Atlas• Distributed Hash Table indexing, using P2P technology to

handle the storage over hundreds of nodes in the Everlab cluster

• Single point for querying systems. SeRQL, RQL and SPARQL interfaces

• We produced sets of web forms, to replicate some typical queries needed for reporting

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Semantic queriesSemantic queries

• Instruments are explicitly modelled in the RDF so we can move from a query about the Radar Altimeter based on an identifier:

?EVENT event_id ?EVENT_ID ;FILTER ( REGEX(?EVENT_ID,".*RA.*"))

• To one explicitly looking for a link to the instrument:?EVENT event_id ?EVENT_ID ;

represents_plan_event ?PLAN_EVENT_TYPE .?PLAN_EVENT_TYPE executed_by_instrument ?INSTRUMENT .?INSTRUMENT instrument_id "RA"

• Simple change, but much more flexible if we have new event types for the instrument, or add more data about it (like power consumption)

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Creating new report types 1/3Creating new report types 1/3

• JSP based system of forms for report designer

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• They also identify the user input fields and the output desired

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• User is presented with web form

• Results generated

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ProblemsProblems

• Grid, and DHT technologies were complicated to set up

• Many legacy data formats, and specific data types

• Missions have similar interfaces and files, but often with small customisations

• Inertia – much easier to introduce these ideas for new systems

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Advantages: ProcessAdvantages: Process

• Integration of data solved well by use of Ontology

• Separation of concerns, between modelling and domain experts

• Semantic level of metadata acquisition and querying means virtually no end user training needed

• Service based architecture – ease of collaborative development and potential for virtual organisations

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Advantages: ResultsAdvantages: Results

• Flexible querying of data from hetereogeneous sources

• All access is virtualised from the user perspective

• Support for Data and Metadata lifecycles

• Clear demonstration for industry that standardising and exposing metadata makes the data much more useful

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QuestionsQuestions

Thanks for listening.

Any Questions?

[email protected]

1 DMS-DQS-SUPSC03-PRE-12-E © DEIMOS Space S.L., 2007 A Semantic Data Grid for Satellite Mission...

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