Up until now, it hasn't been possible to check the syntax of a UCD list
using
XML Schema: there's no way (yet) to express a list of elements
separated by
semi-colons. This is a shame, since it means that somebody else has to
do
this work - work which could have been delegated to the XML parser.
Fortunately, XML Schema recognizes lists of elements separated by white spaces, i.e. not
"phot.calib;src.class"
but
"phot.calib src.class"
If the official syntax of UCD lists included the latter possibility,
then the
entire content of a VO XML document could be parsed at once in a single
pass.
Yes, it's too late for VOTable, but many other schemata are still in
their
infancy and would benefit dramatically from this possibility. While
the use
of UCD in VOTable has - up to now - been mostly in the form of
documentation,
VOEvent needs to be able to permit direct interpretation of the meaning
of
elements identified by UCD's (e.g. your robotic telescope only wants to
look
at GRB's and not vanilla SN). Either all subgroups like VOEvent wil
be forced
to define their own ontology or we enable all VO schemata to be able
to interpret
UCD's directly without any extra effort. The present syntax prevents
this.
Schema examples of how this might work can be found at
http://monet.uni-sw.gwdg.de/twiki/bin/view/VOEvent/ SchemaContentUCDListType
(for the formal UCD list element type) and
http://monet.uni-sw.gwdg.de/twiki/bin/view/UCD/SchemaContentUCD
for an example of the current UCD placed in a schema which could be concatenated in a UCD list element.
In the short term, we can easily afford to let the two forms exists
side by side
(well, VOTable uses the old syntax, and new ones like VOEvent use the
newer
one). Those who have added parsers to read the old UCD lists will
easily be
able to adopt their code to read the new format, and those of us still
working on
the first versions of VO schemata can immediately benefit from being
able to
parse the ENTIRE document.
F. Hessman
C. Hettlage
Dr. Frederic V. Hessman Hessman-at-Astro.physik.Uni-Goettingen.DE Universitaets-Sternwarte Tel. +49-551-39-5052 Geismarlandstr. 11 Fax +49-551-39-5043 37083 Goettingen http://www.uni-sw.gwdg.de/~hessman
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http://monet.uni-goettingen.de
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Andrea Preite Martinez andrea-at-rm.iasf.cnr.it Istituto di Astrofisica Spaziale Tel.:+39.06.4993.4641 Area di Ricerca di Tor Vergata Fax.:+39.06.2066.0188 Via del Fosso del Cavaliere 100 Cell:+39.339.381735500133 Roma