The VOTable, VO Protocols, and UCDsJuan de Dios Santander Vela (IAA-CSIC)
Overview
VOTable, the VO table format
UCDs, UTypes, & column semantics
Simple DAL protocols
Simple ConeSearch
Simple Image Access
Simple Spectral Access
VOTable
VOTable
XML-based metadata (and sometimes, data) format
Allows for things which cannot be done with FITS
Semantic specification
Hierachical resource nesting
Linking (internal and to outside data)
VOTable StructureVOTABLE DESCRIPTION
0..1
DEFINITIONS
0..1
0..
COOSYS
PARAM
INFO
RESOURCE
0..
@ ID
@ version restricts: xs:NMTOKEN
VOTable: COOSYSCOOSYS extends: xs:string @ ID
type: ID from: XMLSchema.xsd
ID restricts: xs:NCName
@ equinox
type: astroYear
astroYear restricts: xs:token
@ epoch
type: astroYear
astroYear restricts: xs:token
@ system restricts: xs:NMTOKEN
base: string from: XMLSchema.xsd
string restricts: xs:anySimpleType whiteSpace : preserve
VOTable: RESOURCERESOURCE DESCRIPTION
0..1
0..
INFO
COOSYS
PARAM
LINK
0..
TABLE
0..
RESOURCE
0..
##other
0..
@ name
@ ID
@ utype
@ type restricts: xs:NMTOKEN
@ ##other
VOTable: TABLETABLE DESCRIPTION
0..1
0..
FIELD
PARAM
GROUP
LINK
0..
DATA
0..1
@ ID
@ name
@ ref
@ ucd
@ utype
@ nrows
VOTable: DATADATA TABLEDATA
BINARY
ref: BINARY
BINARY STREAM
FITS
ref: FITS
FITS STREAM
@ extnum
VOTable: TABLEDATA
TABLEDATA TR
0..
ref: TR
TR TD
1..
VOTable: STREAMSTREAM extends: xs:string @ type restricts: xs:NMTOKEN locator
other
base: NMTOKEN from: XMLSchema.xsd
NMTOKEN restricts: xs:token
@ href
@ actuate restricts: xs:NMTOKEN onLoad
onRequest
other
none
base: NMTOKEN from: XMLSchema.xsd
NMTOKEN restricts: xs:token
@ encoding
type: encodingType
encodingType restricts: xs:NMTOKEN gzip
base64
dynamic
none
base: NMTOKEN from: XMLSchema.xsd
NMTOKEN restricts: xs:token
@ expires
type: dateTime from: XMLSchema.xsd
dateTime
@ rights
type: token from: XMLSchema.xsd
token restricts: xs:normalizedString
base: string from: XMLSchema.xsd
string
Unified Content Descriptor
Unified Content Descriptor (UCD)
Extended unit
Provides broad-range semantics for table columns, and class equivalence
Mandatory attribute (@ucd) for VOTable FIELDs
UCD1+ Tree
arith (arithmetics)em (electromagnetic spectrum)instr (instrument)meta (metadata)obs (observation)phot (photometry)phys (physics)pos (positional data)spect (spectral data) src (source)stat (statistics)time
UTypes
UTypes are tools for direct mapping of columns into datamodels
Allows for VOTable serialisation or complex data models
Additional, optional FIELD attribute (@utype)
We will return to them when we talk about data models
VO Access ProtocolsAccess protocols == DAL protocols
Simple protocolsSimple to queryComplex to build, different protocol per data product type
Simple ConeSearch, Simple Image Access, Simple Spectral AccessCommon data model: CharDM
ConeSearch
endPointURL?RA=rightAscension& DEC=declination& SR=searchRadius& VERB=verbosity
CONESEARCH IS GENERIC:
TABLE FIELDS MUST BE IDENTIFIED
optional
mandatory
Simple Image AccessendPointURL?POS=RA,DEC&SIZE=searchRadius&FORMAT=formatType& INTERSECT=intersectionMechanism&NAXIS=axisSizeVector&CFRAME=coordFrame&EQUINOX=equinoxSpec&CRPIX=refPixCoordVector&CRVAL=refPixValueVector&CDELT=pixScaleVector&ROTANG=rotationAngle&PROJ=projectionKind&VERB=verbosity
optional
mandatory
Simple Spectra AccessendPointURL?POS=ra,dec& SIZE=searchRadius& BAND=freqRange& TIME=timeRange& FORMAT=formatType& SPECRP=specResol& SPATRES=spatialResol& PUBDID=pubID& CREATORDID=creatorID& COLLECTION=collectionID& TOP=topNumResults& MAXREC=maxRecords& MTIME=modificationTime& COMPRESS=compressionFlag& RUNID=jobRunID&
APERTURE=apertAngle& TIMERES=timeResol& SNR=signal2noise& REDSHIFT=redShiftRange& VARAMPL=amplitudeVariability& TARGETNAME=targetName& TARGETCLASS=targetClass& FLUXCALIB=fluxCalibKind& WAVECALIB=waveCalibKind
mandatory
optionalrecommended
VO Access Protocols
SxA Protocols simple to query
But they need a lot of client-side processing for filtering
Table Access Protocol
Direct access to tables
Complex REST interaction
REST:REpresentational State Transfer
References & LinksVOTable format
UCDs
UCD1+ list
UTypes
Simple ConeSearch
Simple Image Access
Simple Spectral Access
Table Access Protocol
