www.g-vo.org

The International Virtual The International Virtual Observatory Alliance Observatory Alliance

(IVOA)(IVOA)interoperability in action

www.g-vo.org

Babylonian confusionBabylonian confusion

SDSS

ROSAT

2MASS

FIRST GAIA

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ROSATFIRST GAIA

SDSS2MASS

EsperantoEsperanto

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IVOA MembersIVOA Members

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IVOAIVOA

• Mission statement“facilitate the international coordination and collaboration necessary for the development and deployment of the tools, systems and organizational structures necessary to

enable the international utilization of astronomical archives as an integrated and interoperating virtual observatory.“

www.g-vo.org

Working and Interest GroWorking and Interest Groupsups

• WGs– Standards and Process: how the IVOA works– Resource registry: where to register and discover resources– Data Modeling: how to describe data sets– Semantics: how to understand one another– VOTable: standard format for tabular data sets– Data Access Layer: very simple data access services– VO Query Language: more sophisticated data access– Grid and web services: programmatic accessibility– Applications: stand alone, and together– VOEvent: astronomical telegrams in XML

• IGs– Theory: virtual observations for virtual universes– Open GridForum Astro-RG: VObs and virtual organisations– Data Curation and Preservation: how not to loose your data

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Resource RegistryResource Registry

• http://www.ivoa.net/twiki/bin/view/IVOA/IvoaResReg

• XML schema: http://www.ivoa.net/Documents/WD/ReR/VOResource-20060620.html

• Implementations:– Searchable Registry at STScI – NCSA Publishing Registry – ESAVO Full Registry

• Client tools:– VOExplorer (AstroGrid)– Splat, SpecView, Aladin

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Data ModelingData Modeling

• http://www.ivoa.net/twiki/bin/view/IVOA/IvoaDataModel

• Describe some standard data products– Data– Metadata !– XML serialisation

• In process:– Space-Time Coordinates– 1D Spectrum (used in SSA)– Characterisation of data sets

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SemanticsSemantics

• http://www.ivoa.net/twiki/bin/view/IVOA/IvoaSemantics

• Provide standard lists of terms• To be used wherever different agents need to

understand each other• UCDs: names of properties• Semantic Vocabularies: astronomical terms

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VOTableVOTable

• http://www.ivoa.net/twiki/bin/view/IVOA/IvoaVOTable

• XML format for tabular data• Column definitions included with data• Binary streams and FITS included• Understood by many client tools (see applications

set)– TOPCAT– VOPlot– Aladin

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VOTable exampleVOTable example

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Data Access Layer IData Access Layer I

• http://www.ivoa.net/twiki/bin/view/IVOA/IvoaDAL • Simple protocols for discovering and retrieving

data sets• Generally HTP-GET based:

– Base url: http://www.g-vo.org/ssa?action=doQuery&archiveid=ssa.service.cdfs

– Query parameters:POS=53.161,-27.832&SIZE=0.2&BAND=0/&TIME=,&FORMAT=ALL

• Returns list of spectra with access URL for retrieving them.

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Data Access Layer IIData Access Layer II

• Examples form GAVO, for more usage examples see tool demos– Simple cone search (source catalogues)

• ROSAT source catalogues and photon event lists)

– Simple Image Access• ROSAT pointed observations and All-Sky

Survey fields

– Simple Spectral Access• Chandra Deep Field South optical follow up

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InteroperabilityInteroperability

Standard services, once registered,

can be found by client tools …

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InteroperabilityInteroperability

….and executedtogether (too

many ROSAT results to show all here!)

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InteroperabilityInteroperability

… and shown together

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VObs Query LanguageVObs Query Language

• http://www.ivoa.net/twiki/bin/view/IVOA/IvoaVOQL• Querying remote databases

– Remote filtering: reduces data to be sent– Combination (even distributed!)

• ADQL– SQL based– Some extra astronomical features

• Databases online– SDSS SkyServer– Millennium database (see demo)

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Grid and web servicesGrid and web services

• http://www.ivoa.net/twiki/bin/view/IVOA/IvoaGridAndWebServices

• Web services can be made accessible to other applications– SOAP/WSDL– REST– Grid

• Needs agreements on– Security: Single-Sign-On– Distributed storage: VOSpace– Standardised components: Universal Worker

Service• But then: distributed workflows !

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VOEventVOEvent

• http://www.ivoa.net/twiki/bin/view/IVOA/IvoaVOEvent

• XML format for messages about sudden events– Where ?– What ?– When ?

• Robotic telescopes might connect to this …• Users can connect to stream and selectively filter

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ApplicationsApplications

• http://www.ivoa.net/twiki/bin/view/IVOA/IvoaApplications

• See various targeted demos:– Aladin (applet)– TOPCAT (webstart)– SpecView (webstart)– …

• Application interoperability: Plastic– Messaging standard– Tying TOPCAT to Aladin to Splat to … – all on your desktop

www.g-vo.org

IG: TheoryIG: Theory

• http://www.ivoa.net/twiki/bin/view/IVOA/IvoaTheory