Standards

S. Derriere, F. Ochsenbein, M. Louys

Standards & interoperability

Long before the VO era, standards have been used in astronomy:

FITS (Flexible Image transport System)

ReadMe (Documentation of astronomical catalogues)

Bibcode (bibliographic reference coding)

ASU (Astronomical Server URL)

AstroRes (using XML)

Interoperability requires standards

in collab.

Standards & interoperability

VO projects require interoperability between components: collaborative definition of standards (IVOA), WGs

VOTable

Registry

UCD

Data access layer

Data Models

Web Services

CDS and standards

CDS expertise in the definition of standards:

Bibcodes: CDS and NED, and later ADS

ReadMe (for VizieR)

ASU and Astrores: CDS with collaborators

CDS is involved in the definition and application of Standards in the VO

Examples in this talk

VOTable

VOTable

Standard for exchanging tabular data:

Uses XML (eXtensible Markup Language: widely used standard)

Interoperable and scalable

Combine metadata and data in the same document

VOTable (history)

Towards a VO standard for table

XML description for tables

Astrores

CDS, ESO, STScI, ADC,

Used in Aladin, HEASARC Browse, OASIS

Visit of R. Williams, NVO system architect, to CDS

VOtables	to be discussed by the ‘XML table’ expert group

Viewgraph from

Nov. 2001

CDS Council

VOTable (history)

Interoperability meeting in Strasbourg (jan. 2002)

... towards VOTable 1.0

VOTable (history)

VOTable 1.0 accepted Apr 15, 2002

VOTable (history)

Interoperability meeting in Boston (may. 2004)

Final discussion of VOTable 1.1

VOTable 1.1 accepted as IVOA recommendation (august 2004)

<?xml version="1.0"?>

<VOTABLE version="1.1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:noNamespaceSchemaLocation="http://www.ivoa.net/xml/VOTable/VOTable/v1.1">

<COOSYS ID="J2000" equinox="J2000." epoch="J2000." system="eq_FK5"/>

<RESOURCE name="myFavouriteGalaxies">

<TABLE name="results">

<DESCRIPTION>Velocities and Distance estimations</DESCRIPTION>

<PARAM name="Telescope" datatype="float" ucd="phys.size;instr.tel"

unit="m" value="3.6"/>

<FIELD name="RA" ID="col1" ucd="pos.eq.ra;meta.main" ref="J2000"

datatype="float" width="6" precision="2" unit="deg"/>

<FIELD name="Dec" ID="col2" ucd="pos.eq.dec;meta.main" ref="J2000"

datatype="float" width="6" precision="2" unit="deg"/>

<FIELD name="Name" ID="col3" ucd="meta.id;meta.main"

datatype="char" arraysize="8*"/>

<FIELD name="RVel" ID="col4" ucd="src.veloc.hc" datatype="int"

width="5" unit="km/s"/>

<FIELD name="e_RVel" ID="col5" ucd="stat.error;src.veloc.hc"

datatype="int" width="3" unit="km/s"/>

<FIELD name="R" ID="col6" ucd="phys.distance" datatype="float"

width="4" precision="1" unit="Mpc">

<DESCRIPTION>Distance of Galaxy, assuming H=75km/s/Mpc</DESCRIPTION>

</FIELD>

<DATA>

<TABLEDATA>

<TR>

<TD>010.68</TD><TD>+41.27</TD><TD>N 224</TD><TD>-297</TD><TD>5</TD><TD>0.7</TD>

</TR>

<TR>

<TD>287.43</TD><TD>-63.85</TD><TD>N 6744</TD><TD>839</TD><TD>6</TD><TD>10.4</TD>

</TR>

<TR>

<TD>023.48</TD><TD>+30.66</TD><TD>N 598</TD><TD>-182</TD><TD>3</TD><TD>0.7</TD>

</TR>

</TABLEDATA>

</DATA>

</TABLE>

</RESOURCE>

</VOTABLE>

Simple VOTable 1.1 example:

METADATA

DATA

VOTable in action

Many libraries to read/write VOTable:

Java (SAVOT*, JAVOT...)

C++ (VO-India)

PERL (NVO)

Tools to visualize VOTable:

VOPlot (VO-India)

TopCat (Starlink)

Mirage (Bell labs)

CONVot for ASCII -> VOTable

VOTable: a key standard for all VO demos !

* Developed at CDS

VOTable & other standards

3 ways to include data in VOTable:

TableData

FITS

Binary

UCD present in VOTable

<FIELD name="RA" ucd="pos.eq.ra">

Link to Data Models (utype)

Registry

Registry for the VO

The goal of the registry is to be able to locate, get details of, and make use of any resource located anywhere in the IVO space

VOResource

OAI (Open Archives Initiative)

Repositories

Harvesters

Registry at CDS

Participation in discussions to define the standard

What metadata are needed?

VizieR repository (all tables exposed)

VizieR resources harvested from other registries (NVO, AstroGRID)

~97% of resources registered at STScI come from VizieR

Registry at CDS

IVOA discussions give a list of resources, not yet the way to query the services

CDS GLU (1997) is a registry, with very useful properties (including query syntax) which are still not available in IVOA registry

Link between the GLU and IVOA Registry is investigated

UCD

Unified Content Descriptors

UCD (history)

UCD = Unified Content Descriptors

Astronomical catalogues have heterogeneous origins, formats and descriptions.

Each author/consortium is free to label columns with its own « column names » and to use fancy units.

CDS ReadMe give a homogenized description of catalogues, keeps column names and units, but give a text description of their contents.

UCD (history)

UCD give a semantic description of column contents

UCD1 : first version derived from the ESO-CDS data mining project

Study of 100,000 VizieR catalogue columns (P.F. Ortiz)

~1500 words

POS_EQ_DEC_MAIN (equatorial declination)

PHOT_JHN_V (V magnitude in Johnson system)

UCD (history)

Available before IVOA

Applications of UCD1:

ConeSearch

Finding catalogues based on their contents

Aladin filters

Aladin filters

UCD1+

Migration to UCD1+ with the VO

More flexible description

IVOA controlled vocabulary

List of standard words and combinations to express semantic meaning:

phot.mag;em.opt.V

stat.error;phys.temperature

pos.eq.dec

UCD1+

IVOA proposed recommendation

UCD1+

Description of atomic and molecular data (collab. M.L. Dubernet)

Use in VOTable 1.1 (UCD attribute)

International board set up by IVOA to manage evolution

Toward an ontology (more on this Friday)

Migration to UCD1+

In VizieR

Upgrade existing tools

UCD1+ at CDS

List of words maintained at CDS

Tools available

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

UCD browser / resolver

Web Services

Web Services

Standard way to exchange data between services (relies on XML)

http://cdsweb.u-strasbg.fr/cdsws.gml

Coordinates transformation

Name resolver (Sesame: Simbad+VizieR)

UCD resolver

Access to VizieR

WS monitoring just implemented at CDS

VOTable Conclusions

SD

2004-09-07T10:49:58

SD