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International Virtual Observatory Alliance |
The UCD1+ controlled vocabulary
Version 1.23
IVOA
Recommendation 2007 April 2
This version:
http://www.ivoa.net/Documents/REC/UCD/UCDlist-20070402.html
Latest version:
http://www.ivoa.net/Documents/latest/UCDlist.html
Previous version(s):
http://www.ivoa.net/Documents/REC/UCD/UCDlist-20051231.html
Editor(s):
A. Preite Martinez, S. Derriere
Author(s):
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Andrea Preite Martinez (andrea.preitemartinez@iasf-roma.inaf.it), |
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Sebastien Derriere
(derriere@astro.u-strasbg.fr), |
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Nausicaa Delmotte (ndelmot@eso.org), |
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Norman Gray (norman@astro.gla.ac.uk), |
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Robert Mann (rgm@roe.ac.uk), |
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Jonathan McDowell (jcm@cfa.harvard.edu), |
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Thomas Mc Glynn (Thomas.A.McGlynn@nasa.gov),
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François Ochsenbein
(francois@astro.u-strasbg.fr), |
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Pedro Osuna (Pedro.Osuna@esa.int), |
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Guy Rixon (gtr@ast.cam.ac.uk), |
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Roy Williams (roy@cacr.caltech.edu) |
This
document describes the list of controlled terms used to build the Unified
Content Descriptors, Version 1+ (UCD1+). The document describing the UCD1+ can be found at the URL: http://www.ivoa.net/Documents/latest/UCD.html. This document reviews the
structure of the UCD1+ and presents the current vocabulary.
This is an IVOA Recommendation. This document
has been produced by the IVOA Semantics Working Group. It has been reviewed by IVOA Members and other
interested parties, and has been endorsed by the IVOA Executive Committee as an
IVOA Recommendation. It is a stable document and may be used as reference
material or cited as a normative reference from another document. IVOA's role
in making the Recommendation is to draw attention to the specification and to
promote its widespread deployment. This enhances the functionality and
interoperability inside the Astronomical Community.
A list of current IVOA Recommendations and other
technical documents can be found at http://www.ivoa.net/Documents/.
This document is based on the W3C
documentation standards as adapted for the IVOA.
The
UCD1+ controlled vocabulary Version 1.23
1 Definition of atoms and words
2 The structure of the UCD1+ tree
Appendix A: List of valid words
Appendix B: Changes from previous versions
Changes from v1.11
(Rec20051231)
1 Definition of atoms and words
A UCD is a string which contains textual tokens called ‘words’,
separated by semicolons(;). A word is composed of
‘atoms’, separated by periods(.). The hierarchy is as
follows:
atoms --> words -->
composed words
UCD1+ are either single words, or a composition
of several words.
UCDs are “controlled” (through a process that is also indicated in the
reference document above). Control is exercised at the level of words (UCD1+)
and at the level of the vocabulary (atoms) used to form words. A consistent
list of atoms will be mantained, making sure that the same atom always means
the same thing, even if used in combination with different other atoms.
1.1 Definition
of atoms
Atoms are defined following these
guidelines:
1. Abbreviations are kept to a minimum, and only if the result is not
ambiguous. (ra, dec are
acceptable, but t is
ambiguous: time and temperature are used instead.)
2. Atoms are not hyphenated. The separation is marked by a capital
letter to help readability (position angle = posAng) unless the composed word has a well known acronym (signal to noise
ratio = snr) or
short form (standard deviation = stdev). There
are only two exception to this rule: (i) the X-ray
band (em.X-ray) and (ii) the frequency /
wavelength intervals defining regions of the e.m. spectrum (e.g. em.radio.3-6GHz).
1.2 Definition
of words
The list of UCD1+ words presented in this document was initially
generated applying the rules and recommendations of PR-UCD-20040823 to
catalogues/tables in VizieR. The original motivation was to transform old UCD1
into an improved version, trying to build a list of combinations of new words
that could describe all the existing UCD1 terms.
The list of UCD1+ words is maintained by the UCD Scientific Board,
following the procedure defined in the UCD Recommendation document (http://www.ivoa.net/Documents/latest/UCD.html), and described in detail in
http://www.ivoa.net/Documents/latest/UCDlistMaintenance.html .
2 The structure of the UCD1+ tree
All existing UCD1+ words are grouped into 12 main categories. These
categories are expressed by the first atom of the word, whose possible values
are:
- arith (arithmetics)
This section includes concepts
involving or indicating some mathematical operation performed on the primary
‘concept’ or just the presence of an arithmetic factor or operator.
- em (electromagnetic spectrum)
This section describes the
electromagnetic spectrum, either in a monochromatic way or in predefined
intervals. The complete list of proposed bands (in seven classical regions of
the e.m. spectrum: radio, millimeter, infrared,
optical, ultraviolet, x-ray and gamma-ray), can be found in the document Note-EMSpectrum-20040520
- instr (instrument)
This section includes all quantities
related to astronomical instrumentation, e.g. detectors (plates, CCDs, etc.),
spectrographs, and telescopes (including observatories or missions), etc.
- meta (metadata)
This section includes all the
information that is not coming directly from a measurement, and information
that could not be included in other sections.
- obs (observation)
In principle under this section
should go all words describing an observation (the name of the observer or PI,
the observing conditions, the name of the field). In
practice, the section is very ‘thin’ and could be deleted, if the sparse
content could be housed elsewere.
- phot (photometry)
All the words describing photometric
measures are included in this section. The definitions distinguish between a
flux density (flux per unit frequency interval), a flux density integrated over
a given e.m. interval (flux if expressed linearly, mag
if expressed by a log), or a flux expressed in counts/s (if the setup of the
detector is photon counting observing mode). ‘Colors’, which are differences of
magnitudes (i.e. ratios of fluxes) measured in different bandpasses, are also
included.
- phys (physics)
This section includes atomic and
molecular data (mainly used for spectroscopy) and basic physical quantities
(temperature, mass, gravity, luminosity, etc.)
- pos (positional data)
This section describes all
quantities related to the position of an object on the sky:
- Angular coordinates, and projections from spherical to
rectangular systems.
- Angular
measurements in general (the angular size of an object is in this
section, its linear size is in the phys
section).
- The WCS FITS keywords.
9. spect (spectral data)
For historical reasons, photometric
data taken in narrow spectral bands with instruments called spectrographs are
classified as spectroscopic data. These definitions should not be confused with
those in the em
category. em represents the independent variable, or dispersion axis, and phot and spect describe the dependent variable, or flux axis.
- src (source)
This is a rather generic section,
mainly devoted to source classifications. Variability, orbital, and velocity
data are also included in this section.
- stat (statistics)
This section includes statistical
information on measurements.
- time (time)
Quantities related to time (age,
date, period, etc.) are described in this section.
Appendix A: List of valid words
All words are preceded by a ‘syntax’ code that can help in the process
of building composed UCD1+.
- The code “P”
means that the word can only be used as “primary” or first word;
- “S” stands for
only secondary: the word cannot be used as the first word to describe a
single quantity;
- “Q” means that
the word can be used indifferently as first or secondary word;
- “E” means a
photometric quantity, and can be followed by a word describing a part of
the electromagnetic spectrum
- “C” is a colour
index, and can be followed by two successive word describing a part of the
electromagnetic spectrum;
- “V” stands for
vector. Such a word can be followed by another describing the axis or
reference frame in which the measurement is done
Q | arith | Arithmetic quantitiesS | arith.diff | Difference between two quantities described by the same UCDP | arith.factor | Numerical factorP | arith.grad | GradientP | arith.rate | Rate (per time unit)S | arith.ratio | Ratio between two quantities described by the same UCDQ | arith.zp | Zero pointS | em | Electromagnetic spectrumS | em.radio | Radio part of the spectrumS | em.radio.20-100MHz | Radio between 20 and 100 MHzS | em.radio.100-200MHz | Radio between 100 and 200 MHzS | em.radio.200-400MHz | Radio between 200 and 400 MHzS | em.radio.400-750MHz | Radio between 400 and 750 MHzS | em.radio.750-1500MHz | Radio between 750 and 1500 MHzS | em.radio.1500-3000MHz | Radio between 1500 and 3000 MHzS | em.radio.3-6GHz | Radio between 3 and 6 GHzS | em.radio.6-12GHz | Radio between 6 and 12 GHzS | em.radio.12-30GHz | Radio between 12 and 30 GHzS | em.mm | Millimetric part of the spectrumS | em.mm.30-50GHz | Millimetric between 30 and 50 GHzS | em.mm.50-100GHz | Millimetric between 50 and 100 GHzS | em.mm.100-200GHz | Millimetric between 100 and 200 GHzS | em.mm.200-400GHz | Millimetric between 200 and 400 GHzS | em.mm.400-750GHz | Millimetric between 400 and 750 GHzS | em.mm.750-1500GHz | Millimetric between 750 and 1500 GHzS | em.mm.1500-3000GHz | Millimetric between 1500 and 3000 GHzS | em.IR | Infrared part of the spectrumS | em.IR.J | Infrared between 1.0 and 1.5 micronS | em.IR.H | Infrared between 1.5 and 2 micronS | em.IR.K | Infrared between 2 and 3 micronS | em.IR.3-4um | Infrared between 3 and 4 micronS | em.IR.4-8um | Infrared between 4 and 8 micronS | em.IR.8-15um | Infrared between 8 and 15 micronS | em.IR.15-30um | Infrared between 15 and 30 micronS | em.IR.30-60um | Infrared between 30 and 60 micronS | em.IR.60-100um | Infrared between 60 and 100 micronS | em.IR.NIR | Near-Infrared, 1-5 microns
S | em.IR.MIR | Medium-Infrared, 5-30 microns
S | em.IR.FIR | Far-Infrared, 30-1000 micronsS | em.opt | Optical part of the spectrumS | em.opt.U | Optical band between 300 and 400 nmS | em.opt.B | Optical band between 400 and 500 nmS | em.opt.V | Optical band between 500 and 600 nmS | em.opt.R | Optical band between 600 and 750 nmS | em.opt.I | Optical band between 750 and 1000 nmS | em.UV | Ultraviolet part of the spectrumS | em.UV.10-50nm | Ultraviolet between 10 and 50 nmS | em.UV.50-100nm | Ultraviolet between 50 and 100 nmS | em.UV.100-200nm | Ultraviolet between 100 and 200 nmS | em.UV.200-300nm | Ultraviolet between 200 and 300 nmS | em.UV.FUV | Far-UltravioletS | em.X-ray | X-ray part of the spectrumS | em.X-ray.soft | Soft X-ray (0.12 - 2 keV)