Vocabularies:

1

Semantics Session 1 (mon 19, 1630-1800,
Vulcania 1)

• Vocabularies
• Overview of vocabulary document (APM)
• Discussion to resolve WD open issues (NG, AG,
  ...)
• Contributions
• Mapping between Vocabulary terms (A. Gray)
• Towards an IVOA Vocabulary (APM, NG, SD, ...)
• Publishing and maintaining vocabularies (NG ...)

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Status

• July2007 vocabs in XML format ucd-like syntax
• October2007 agreement on the standard W3C format
  RDF and SKOS
• March2008 WD Vocabularies in the Virtual
  Observatory v1.00
• Open Issues discuss and validate them
• WDv1.0 gt PRv1.1

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Vocabularies Open Issuessee summary Note by NG
athttp//www.astro.gla.ac.uk/users/norman/ivoa/vo
cabularies/issues

• Semantics Session 1

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Vocabularies Open Issues

1. Format of the master vocabulary CLOSED?
2. Format of the distributed vocabularies CLOSED?
3. Identifying vocabulary versions
4. Who maintains vocabularies? CLOSED?
5. What vocabularies are included in the standard?
   CLOSED?
6. Inclusion of mappings in vocabularies

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1. Format of the master vocabulary

• what should be the format of the master files?
• Possible resolution 1 nothing mandated in the
  document -- the format of the master file should
  be whatever is most convenient, as long as the
  generated and distributed files are valid SKOS.
• Possible resolution 2 SKOS, in Turtle notation,
  possibly requiring some post-processing to add
  omitted-but-inferrable relations. This is easy
  to read and write, and it is simple enough that
  it would be feasible to create from scratch a
  parser for the relevant subset of it.
• Possible resolution 3 some more fundamental
  no-punctuation format, such as that for the
  Lexicon program.
• Provisional resolution option (1) above
  nothing mandated. Only the distribution format
  is to be specified (no objections on the list).

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2. Format of the distributed vocabularies

• in which format should vocabularies be
  distributed?
• Possible resolution 1 the standard simply
  mandates that they be distributed in at least one
  well-known RDF format (which means either RDF/XML
  or Turtle, which is equivalent to N3 for this
  purpose). This implies that an RDF parser will,
  realistically, be required in order to process
  the vocabulary files.
• Possible resolution 2 the standard requires them
  to be distributed in a format which is parseable
  as RDF, but which is also regular enough that
  it's usefully interpretable as normal XML.
• Provisional resolution option (1) above
  distribution in any RDF serialization.

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3. Identifying vocabulary versions

• do vocabulay users refer to a concept URI with
  explicit version, or to a constant URI which
  always refers to the latest version?
• Possible resolution 1 users always refer to the
  same concept URI, as for example in
  http//myvocab.org/myvocabmytoken, and this
  refers to the latest version of the vocabulary.
  The Dublin Core metadata set does this.
• Possible resolution 2 users refer to a concept
  URI without a version this URL returns a
  vocabulary with a versioned namespace (it
  violates good practice)
• Possible resolution 3 users will refer to
  concepts which have a version explicit within the
  namespace, as for example in http//myvocab.org/my
  vocab-v1.1mytoken (the precise location of the
  version number or date in the URI is a
  distribution/maintenance detail).

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4. Maintenance (1/2)

• By whom, and by what process, are vocabularies
  maintained?
• Option 1 the vocabularies in the standardized
  document are regarded purely as examples, with no
  normative force and no specified maintenance
  process.
• Option 2 the document's vocabularies are
  normative, and the document should define a
  maintenance process, possibly modelled on the UCD
  process.
• Option 3 the document's vocabularies are
  normative, but not claimed to be more than merely
  adequate. They will not be developed as part of
  this standard's evolution, but instead be
  maintained by other interest groups, either
  within or without the IVOA process.

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4. Maintenance (2/2)

• Are there minimal standards of curation which
  conforming vocabularies must abide by? For
  example, need we require vocabulary maintainers
  to use the ltskoschangeNotegt mechanisms, or just
  rely on their good sense?
• Provisional resolution Option 3. The final
  published standard will include a number of SKOS
  vocabularies produced as part of this process.
  These will be usable and citable, and the
  community will be encouraged to use them, but
  they will not be maintained after the standard is
  complete. Instead, the owners' of the
  underlying vocabularies (for example the UCD
  maintenance group) will be encouraged to maintain
  the SKOS version alongside their other forms. In
  particular, the IVOA-T vocabulary will be
  developed and maintained in a parallel standard
  to this one.

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5. What vocabularies are included in the
standard? (1/2)

• There are six vocabularies which have been
  associated with the draft standardization
  process, namely
• the AA journal keyword list, the IVOA AOIM list,
  and the 1993 IAU thesaurus, whose inclusion
  should be completely uncontroversial
• an IVOA Thesaurus based on the IAU-93, which may
  or may not be in this standard depending on
  whether people would prefer a completely separate
  process to develop it
• a UCD1 vocabulary (though this deals with a
  different set of concepts namely data types
  from the other vocabularies and might arguably
  connect poorly to them) and
• a SKOS version of the list of constellations,
  which is very simple, and which might reasonably
  find a home in this standard on that ground alone.

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5. What vocabularies are included in the
standard? (2/2)

• In addition, there are multiple informal keyword
  lists associated with VOEvent. These haven't been
  SKOSified at all, and Rick's excellent suggestion
  is that these be left as homework for the VOEvent
  group. Plus Theory/Simulations..
• Provisional resolution include all five/six.
  The AA, AOIM, UCD1, IAU-93 and constellations
  vocabularies will be finished and immediately
  useable. The IVOAT vocabulary will be developed
  in a parallel process to this vocabularies
  standard it will be referred to, and a snapshot
  of it may be included in the standard, but it
  will be clearly marked as a work-in-progress.

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6. Inclusion of mappings in vocab.s (1/2)

• Consideration 1 The mappings spec is still in
  flux, and likely to remain so for some time after
  the SKOS core document is standardized
• Consideration 2 the situation could develop
  where there are multiple third-party mappings
  between vocabularies, maintained by specific
  communities, or which describe mappings at
  different levels of granularity, or which
  represent significant labour on the part of
  individuals, adding value to the network of
  vocabularies.

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6. Inclusion of mappings in vocab.s (2/2)

• Suggested resolution include mappings as
  non-normative parts of this standard, published
  alongside, but separate from, the normative SKOS
  versions of the vocabularies, and using whatever
  are the then-current best mapping practices. In
  this standard, and in the best-practice
  guidelines we include, we should proscribe
  inter-vocabulary mappings being published as part
  of a vocabulary.
• Vocabularies and the mappings between them are
  conceptually separate entities, although they
  will in practice likely be maintained together