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\title{The CDS Hub}
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\author{Fran\c{c}oise Genova, Mark G. Allen, Thomas Boch, Fran\c{c}ois Bonnarel,
Laurent Cambr\'esy, S\'ebastien Derriere, Pascal Dubois, Pierre
Fernique, Soizick Lesteven, Ana\"is Oberto, Fran\c{c}ois
Ochsenbein, Andrea Preite Martinez, Andr\'e Schaaff, Bernd
Vollmer, Marc Wenger} \affil{Centre de Donn\'es astronomiques de
Strasbourg, Observatoire astronomique, UMR 7550, 11 rue de
l'Universit\'e, 67000 Strasbourg, France}
\author{Mireille Louys}
\affil{LSIIT, UMR 7005, Parc d'Innovation, Boulevard S\'ebastien
Brant, BP 10413, 67412 Strasbourg, France}
\author{Emmanuel Davoust}
\affil{LATT, UMR 5572, Observatoire Midi Pyr\'en\'ees, 14 avenue
Edouard Belin, 31400 Toulouse}
\author{G\'erard Jasniewicz}
\affil{GRAAL, UMR 5024, Universit\'e de Montpellier II, 34095
Montpellier Cedex 05, France}

\contact{Fran\c{c}oise Genova} \email{genova@astro.u-strasbg.fr}

\paindex{Genova, F.}
\aindex{Allen, M. G.}     % Remove this line if there is only one author
\aindex{Boch, T.} 
\aindex{Bonnarel, F.} 
\aindex{Cambr\'esy, L.}
\aindex{Derriere, S.} 
\aindex{Dubois, P.} 
\aindex{Fernique, P.}
\aindex{Lesteven, S.} 
\aindex{Oberto, A.} 
\aindex{Ochsenbein, F.}
\aindex{Preite Martinez, A.} 
\aindex{Schaaff, A.} 
\aindex{Vollmer, B.} 
\aindex{Wenger, M.} 
\aindex{Louys, M.} 
\aindex{Davoust, E.}
\aindex{Jasniewicz, G.}

\authormark{Genova et al. }

\keywords{databases, information: services, Virtual Observatory, standards}

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\begin{abstract}          % Leave intact
The status of the CDS services is described. In particular, new
features developed in the context of the Virtual Observatory and
using IVOA-discussed standards have been included in the public
version of the services, e.g., filter capabilities using Unified
Content Descriptors (UCDs) in VizieR and Aladin, customized
hierarchical data tree using the IDHA data model, contour plots
and colour composition in Aladin, and others. Aladin has also been
made easy to interface with Java plug-ins, as shown with VOPlot,
the table data visualizer developed by VO-India in collaboration
with CDS, which is also interfaced with VizieR.
\end{abstract}

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\section{Introduction }

\htmladdnormallink{CDS}{http://cdsweb.u-strasbg.fr/} is one of the
major players of the International Virtual Observatory (VO)
endeavour, and its services are important building blocks of the
VO. VizieR and Aladin are respectively prototypes of federation
and integration of heterogeneous resources. Several recent
developments of the CDS services have been implemented for the
scientific demonstrations of the VO projects, in particular of the
European Astrophysical Virtual Observatory (AVO). They take full
advantage of the new interoperability standards discussed in the
frame of the International Virtual Observatory Alliance, and allow
also for testing the evolution of these standards.

\section{SIMBAD}

\htmladdnormallinkfoot{SIMBAD}{http://simbad.u-strasbg.fr/Simbad}
provides reference data for more than 3,150,000 astronomical
objects (end December 2003). SIMBAD is continuously updated from
catalogues and published literature and increases by 100,000 to
200,000 new objects and 5,000 new references every year. Recent
updates include the list of observations of the ISO satellite and
links to the variable star data base of the American Association
of Variable Star Observers. A long term action is under way, for
the proper cross-identification of radio catalogues, taking into
account source spectral properties. The help of G. Paturel (LEDA),
J. MacConnel (STScI), W. Osborn (Central Michigan University) and
B. Skiff for the improvement of data on galaxies, Carbon stars,
globular cluster and open cluster stars respectively is also
gratefully acknowledged.

SIMBAD is undergoing its fourth major software upgrade, from a
proprietary database system to the freeware PostgreSQL system,
which will insure a better long-term maintainability. SIMBAD has
been a pioneer of interoperability, with the early release of
SIMBAD name resolver which is now widely used, together with the
NED one, by observatory archives and the ADS to translate an
object name into its position or a bibliographic list. A VOtable
output will soon be released in order to improve its
interoperability in the VO context.

\section{VizieR}

\htmladdnormallinkfoot{VizieR}{http://vizier.u-strasbg.fr/}
provides access and query facilities to about 4,000 catalogues and
tables published in articles. This number increases by about 300
new catalogues every year. New large catalogues include the UCAC2,
2MASS all-sky release and DENIS second release. Logs of ground-
and space-based observatories are also included and regularly
updated (e.g. recently ESO, XMM). Several catalogues and mission
logs provide access to images, spectra and time series, either
located locally in Strasbourg or distributed by remote observatory
data services.

VizieR provides several output formats which allow a great
flexibility in the query result usage: XML and Tab Separated Value
output can be re-injected into another query. VizieR is fully
integrated in the VO world: it provides a VOTable output, and
metadata visibility is improved by the possibility of displaying
the Unified Content Descriptors (UCDs) associated to every column
in a table. In addition, the relevance and usability of new
possible definitions of UCDs (Derriere et al. 2004) are actively
being tested on VizieR data. Taking advantage of VOTable output
and of the international VO collaboration, one VizieR output is a
catalogue column visualization with the VOPlot tool (Kulkarni,
Kembhavi \& Kale 2004), developed by VO-India in collaboration
with CDS, which can be used as an applet. The implementation of
very large catalogues on a PC cluster is also studied (Ochsenbein
et al. 2004).

\section{Aladin}

\htmladdnormallinkfoot{Aladin}{http://aladin.u-strasbg.fr/aladin.gml}
evolution in the last years (Boch, Bonnarel \& Fernique 2004) has
been strongly linked to the development of VO prototypes, in
particular for the AVO project, and has also taken advantage of
the \emph{Images Distribu\'ees H\'et\'erog\`enes en Astronomie}
(IDHA) project. The visualization of multispectral images has been
improved, with implementation of colour composition and contour
plots; filters allow to select and compute derived values from
catalogue data for display, possibly using UCDs - for example
proper motions or colour indices from actual photometry.
Astrometric recalibration is also possible. New data sets have
been added in the local Aladin image database, e.g. 2MASS and
additional colours from DSS and MAMA digitization. All Aladin
operations can be driven by script commands, enabling automatized
processing.

In the VO context, Aladin is fully compatible, as client and
server, with the Simple Image Access protocol. A view of the IDHA
data model allows users to visualize a hierarchical data tree
(Allen et al. 2004), with a browser giving access to appropriate
metadata at each level of the tree. The software has been adapted
to allow for easy interaction of VOTable and FITS compliant
external JAVA applications, with a first application in the AVO
January 2003 demonstration (Quinn et al. 2004) to the Spectral
Energy Distribution tool developed by ESO and the Astronomy
Catalogue Extractor developed by AstroGrid (running SExtractor).
The first application in the Aladin public version is the plug-in
of VOPlot.

\section{Web Services at CDS}

Several key CDS services have been made available as
\htmladdnormallinkfoot{Web
Services}{http://cdsweb.u-strasbg.fr/cdsws.gml} (Schaaff 2004):
name resolver (including SIMBAD and VizieR names), VizieR access,
astronomical coordinates translation, UCD resolver and access to
the UCD list, GLU tag resolution. Additional services will be made
available in the future when needed.





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\acknowledgments{Several of these developments have been funded by
the European Commission though the {\it Astrophysical Virtual
Observatory} RTD project, and by the French {\it Minist\`ere de la
Recherche} through the {\it Images Distribu\'ees H\'et\'erog\`enes
en Astronomy} project (ACI GRID 2001). The discussion of
interoperability standards in IVOA is partially supported by the
European Commission OPTICON Thematic Network.}



\begin{references}

\reference Allen, M.G., Bonnarel, F., Boch, T., Fernique, P.,
    Louys, M.\ \& the AVO team 2004, \adassxiii, \paperref{P3-2}\ok

\reference Boch, T., Bonnarel, F.\ \& Fernique, P.\ 2004,
    \adassxiii, \paperref{P2-32}\ok

\reference Derriere, S., Gray, N., McDowell, J., Mann, R.G.,
Ochsenbein, F., Osuna, P., Preite Martinez, A., Rixon, G.T.\ \&
    Williams, R.\ 2004, \adassxiii, \paperref{P3-17}

\reference Kulkarni, P., Kembhavi, A.\ \& Kale, S.\ 2004,
    \adassxiii, \paperref{P3-26}\ok

 \reference Ochsenbein, F., Derriere, S., Nicaisse, S.\
    \& Schaaff, A.\ 2004, \adassxiii, \paperref{P1-13}\ok

\reference Quinn, P.\ et al.\ 2004, \adassxiii, \paperref{P3-13}

\reference Schaaff, A.\ 2004, \adassxiii, \paperref{P3-20}

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