Information on Service 'UCD Query'
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Further access options are discussed below
The Unified Content Descriptor (UCD) is a formal vocabulary
astronomical data that is controlled by the International Virtual
Observatory Alliance (IVOA). The vocabulary is restricted in order to
avoid proliferation of terms and synonyms, and controlled in order to
avoid ambiguities as far as possible. It is intended to be flexible,
so that it is understandable to both humans and computers. UCDs
describe astronomical quantities, and they are built by combining
words from the controlled vocabulary.
For a list of all services and tables belonging to this service's
resource, see Information on resource 'UCD Query'
Service Documentation
The Unified Content Descriptor (UCD) is a formal vocabulary for astronomical data that is controlled by the International Virtual Observatory Alliance (IVOA). The vocabulary is restricted in order to avoid proliferation of terms and synonyms, and controlled in order to avoid ambiguities as far as possible. It is intended to be flexible, so that it is understandable to both humans and computers. UCDs describe astronomical quantities, and they are built by combining words from the controlled vocabulary.
A UCD does not define the units nor the name of a quantity, but rather "what sort of quantity is this?"; for example phys.temperature represents a temperature, without implying a particular unit.
It would be possible to describe astronomical data quantities in a natural language such as English or Hungarian or Uzbek; however, it would be very difficult to expect a machine to 'understand' it in any sense. At the opposite extreme, there is an attempt within the IVOA to describe astronomical data in terms of a hierarchical data model, so that there is a place for everything, and everything is in its place. The UCD vocabulary falls between these extremes, and is intended to be understandable to both humans and computers.
Overview
You can access this service using:
-
form --
an interface for web browsers through an HTML form
This service is published as follows:
- Within the
set(s) local with the renderer
form
local means it is listed on our front page,
ivo_managed means
it has a record in the VO registry.
Default Output Fields
The following fields are contained in the output by default. More
fields may be available for selection; these would be given below
in the VOTable output fields.
| Name | Table Head |
Description | Unit | UCD |
|---|
| ucd |
UCD |
Unified Content Descriptors from IVOA
|
N/A |
N/A |
| ucd_desc |
Description. |
The simple explaination of UCD
|
N/A |
N/A |
VOTable Output Fields
The following fields are available in VOTable output. The verbosity
level is a number intended to represent the relative importance
of the field on a scale of 1 to 30. The services take a VERB argument.
A field is included in the output if their verbosity level is
less or equal VERB*10.
| Name | Table Head |
Description | Unit | UCD |
Verb. Level |
|---|
| ucd |
UCD |
Unified Content Descriptors from IVOA
|
N/A |
N/A |
20 |
| ucd_desc |
Description. |
The simple explaination of UCD
|
N/A |
N/A |
20 |
Copyright, License, Acknowledgements
The data List of UCD obtained from ucd1p-words-20070402.txt
(http://cdsweb.u-strasbg.fr/UCD/).
VOResource XML (that's something exclusively for VO nerds)
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