The document discusses the VOTable format, which is an XML format for encoding astronomical metadata and data tables. It allows for semantic specification of data through mechanisms like UCDs and UTypes. Simple data access protocols are also covered, including Simple Cone Search, Simple Image Access, and Simple Spectral Access, which define common ways to query astronomical data via parameters. The Table Access Protocol provides direct access to astronomical tables via more complex REST interactions.

1. The VOTable, VO Protocols,
and UCDs
Juan de Dios Santander Vela (IAA-CSIC)

2. Overview
VOTable, the VO table format
UCDs, UTypes, & column semantics
Simple DAL protocols
Simple ConeSearch
Simple Image Access
Simple Spectral Access

3. VOTable

4. 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)

5. VOTable Structure
VOTABLE DESCRIPTION
0..1
DEFINITIONS
0..1
COOSYS
0.. PARAM
INFO
RESOURCE
0..
@ ID
@ version restricts: xs:NMTOKEN

6. VOTable: COOSYS
COOSYS extends: xs:string @ ID
ID restricts: xs:NCName
type: ID from: XMLSchema.xsd
@ equinox
astroYear restricts: xs:token
type: astroYear
@ epoch
astroYear restricts: xs:token
type: astroYear
@ system restricts: xs:NMTOKEN
string restricts: xs:anySimpleType whiteSpace : preserve
base: string from: XMLSchema.xsd

7. VOTable: RESOURCE
RESOURCE DESCRIPTION
0..1
INFO
0.. COOSYS
PARAM
LINK
0..
TABLE
0..
RESOURCE
0..
##other
0..
@ name
@ ID
@ utype
@ type restricts: xs:NMTOKEN
@ ##other

8. VOTable: TABLE
TABLE DESCRIPTION
0..1
FIELD
0.. PARAM
GROUP
LINK
0..
DATA
0..1
@ ID
@ name
@ ref
@ ucd
@ utype
@ nrows

9. VOTable: DATA
DATA TABLEDATA
BINARY
BINARY STREAM
ref: BINARY
FITS
FITS STREAM
@ extnum
ref: FITS

10. VOTable: TABLEDATA
TABLEDATA TR
TR TD
0..
1..
ref: TR

11. VOTable: STREAM
STREAM extends: xs:string @ type restricts: xs:NMTOKEN locator
other
NMTOKEN restricts: xs:token
base: NMTOKEN from: XMLSchema.xsd
@ href
@ actuate restricts: xs:NMTOKEN onLoad
onRequest
other
none
NMTOKEN restricts: xs:token
base: NMTOKEN from: XMLSchema.xsd
@ encoding
encodingType restricts: xs:NMTOKEN gzip
base64
dynamic
none
NMTOKEN restricts: xs:token
base: NMTOKEN from: XMLSchema.xsd
type: encodingType
@ expires
dateTime
type: dateTime from: XMLSchema.xsd
@ rights
token restricts: xs:normalizedString
type: token from: XMLSchema.xsd
string
base: string from: XMLSchema.xsd

12. 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

13. 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

14. 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

15. VO Access Protocols
Access protocols == DAL protocols
Simple protocols
Simple to query
Complex to build, different protocol per
data product type
Simple ConeSearch, Simple Image Access,
Simple Spectral Access
Common data model: CharDM

16. ConeSearch
endPointURL?
RA=rightAscension&
DEC=declination& mandatory
SR=searchRadius&
VERB=verbosity optional
:
ERIC IED
GEN NTIF
RC H IS E
SEA UST B E ID
C ONE M
DS
FIEL
TA BLE

17. Simple Image Access
endPointURL?
mandatory
POS=RA,DEC&
SIZE=searchRadius&
FORMAT=formatType&
INTERSECT=intersectionMechanism&
NAXIS=axisSizeVector&
CFRAME=coordFrame&
EQUINOX=equinoxSpec&
CRPIX=refPixCoordVector&
CRVAL=refPixValueVector& optional
CDELT=pixScaleVector&
ROTANG=rotationAngle&
PROJ=projectionKind&
VERB=verbosity

18. Simple Spectra Access
endPointURL?POS=ra,dec& APERTURE=apertAngle&
SIZE=searchRadius& TIMERES=timeResol&
BAND=freqRange& SNR=signal2noise&
TIME=timeRange& REDSHIFT=redShiftRange&
FORMAT=formatType& VARAMPL=amplitudeVariability&
SPECRP=specResol& TARGETNAME=targetName&
SPATRES=spatialResol& TARGETCLASS=targetClass&
PUBDID=pubID& FLUXCALIB=fluxCalibKind&
CREATORDID=creatorID& WAVECALIB=waveCalibKind
COLLECTION=collectionID&
TOP=topNumResults&
MAXREC=maxRecords& mandatory
MTIME=modificationTime& recommended
COMPRESS=compressionFlag& optional
RUNID=jobRunID&

19. VO Access Protocols
SxA Protocols simple to query
But they need a lot of client-side processing for
filtering
Table Access Protocol REST:
REpresentational State
Transfer
Direct access to tables
Complex REST interaction

20. References & Links
VOTable format Simple ConeSearch
UCDs Simple Image Access
UCD1+ list Simple Spectral
Access
UTypes
Table Access Protocol