F. Genova, VO as a Data Grid, 2003/06/30 1

Interoperability of astronomy data bases

Françoise Genova, CDS

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Astronomy

• A small discipline

• Few commercial constraints

• A long term partnership to define exchange standards and links

FITS: early data exchange format

on-line information in astronomy:

from observations to results

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An early example of interoprerability: Name resolver

Object name >> position

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Evolving world - Web Services - Very Large Surveys

Simbad Name Resolver>> Sesame Web Service

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Web Services as building blocks

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The astronomy bibliographic network

Links between

– electronic journals– the ADS bibliographic database– on-line services (SIMBAD, NED)– … archival data/published results

bibcode e.g. 1999A&A...351.1003G

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References in anon-line article

links to ADS

quality check

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ADS

- Abstracts- Scanned articles- Links to original on-line paper- Links to other, distributed information e.g. original observations- Also-read articles

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ADS

From bibliographyTo the originalobservations

Search an author’s publications

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HST archiveFrom observationTo publication

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A&A on line

From publication to SIMBAD and more

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SimbadInformationAbout the object

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Links To high energyobservations inHEASARC,To Catalogues

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Links from object names in journals: an early example: IBVS

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Links to images and data

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GCVS

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Lessons learnt• De facto standard

SIMBAD/NED, ADS, journals, archives

• Cooperation between all the actors+ snowball effectJournals, ADS, data centres, archive centres

• The community is trained (everyday tools)• Easy-to-build link

but contents / validation are fundamentalthe role of experts remains fundamental for

building value-added services

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Data federationTabular data in astronomy

A common description for tabular data– Reference catalogues– Published tables– Surveys– Catalogues of observations in archives

ReadMephysical organization contents

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ReadMe

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Tables published in articles are usable data!

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Links to observational data (images, spectra, time series), often distributed in observatory archives

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An homogenized view of heterogeneous informationWith links to data

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Towards data integration

• XML

• VOTable > Roy’s talk

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HEARSARCBrowse

Astroresin action!

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With a touch of GLU

Générateur de Liens Uniformes

• Resource dictionary (shared, distributed, hierarchical name space, clone management…), knows the query syntax

• Resolver: symbolic name > URL• An early registry prototype with many of

the required functionalities (conversions, failure tests, …)

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Observations from European archivesInclusive: NASA missions HST, Chandra, surveys, …

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Glu Tag Resolver

Symbolic name >> URL

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Data mining: the Uniform Content Descriptors

• A set of UCDs has been first developed in the frame of the ESO/CDS Data Mining project to describe VizieR catalogue columns (100.000 columns, 1.300 UCDs)

• Name for concept• Assigned semi-automatically using column label,

description and unit• Used e.g. to check the coherence of information in

tables

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UCD browser

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UCD+units: conversion, selection

Select catalogues & target

Join on UCDs :

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Colour excess characterizes carbon stars

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http://cdsweb.u-strasbg.fr/UCD/

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Extension of UCDs

• SDSS: 1.500 columns– Manual verification needed– Very few additional UCDs

• On-going:– UCDs for VOX– UCDs for IDHA data modelAdd ‘Metadata’ branch … FITS keywords are often not accurate

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Validation, maintenance

• A new structure

• Prune the existing UCD tree

• UCD steering group– Proposal in October 2003– UCD V1.0– Evolution mechanism

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The future

• Other knowledge basis– List of object names– Journal keywords– Thesaurus (built by librarians)…

Astronomy described with different points of view

Converging towards an ontology of astronomy??