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12 <title>Issues list: Vocabularies in the Virtual Observatory</title>
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46 ><img alt="IVOA logo"
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51
52 <h1 property="dc:title">Issues list: Vocabularies in the Virtual Observatory</h1>
53 <h2>IVOA Note</h2>
54
55 <dl>
56 <dt>Working Group</dt>
57 <dd><em><a href="http://www.ivoa.net/twiki/bin/view/IVOA/IvoaSemantics">Semantics</a></em></dd>
58
59 <dt>This version</dt>
60 <dd>Issues as of $Revision$, $Date$</dd>
61
62 <dt>Editors</dt>
63 <dd><a href='http://nxg.me.uk/norman/#norman'
64 property='dc:creator' >Norman Gray</a></dd>
65
66 <!--
67 <dt>Authors</dt>
68 <dd>
69 </dd>
70 -->
71
72 </dl>
73
74 <h2><a id="contents" name="contents">Table of Contents</a></h2>
75 <?toc?>
76 <hr/>
77
78 <div class='section'>
79 <p class='title'>Introduction</p>
80
81 <p>This is the list of major issues for the vocabularies work; this
82 does not include minor issues more concerned with the fine details of
83 maintaining and distributing the vocabularies; such minor issues might
84 be better handled using the
85 <a href='http://code.google.com/p/volute/issues/list' >Volute issues
86 list</a>.</p>
87
88 <p>The list is present here as a record of the points at general
89 issue, and (post standardisation) as a reference pointing to some
90 rationale for the design decisions in the standardised document.</p>
91
92 </div>
93
94 <div class='section' id='issueslist'>
95 <p class='title'>The issues list</p>
96
97 <p>The sections below are intended to be a log of the various options
98 and eventual conclusions, rather than a summary of the arguments. For
99 those, see the linked online discussions.</p>
100
101 <p>Some of the issues below have <q>provisional resolutions</q>.
102 These are believed to capture the sense of the on-list discussion,
103 without being final.</p>
104
105 <div class='section-nonum' id='masterformat-1'>
106 <p class='title'>[masterformat-1] Format of the master vocabulary</p>
107
108 <p><em>[Issue summarised here in some detail since it hasn't had much
109 airing on-list]</em></p>
110
111 <p>The distributed (and normative) SKOS files are generated to a
112 greater or lesser extent. This might consist of a conversion from
113 some completely different format, such as the IAUT files which
114 originate in the easily-parsed native format of the Lexicon
115 application which originally managed them (see Shobbrook and Shobbrook
116 <a href='http://www.mso.anu.edu.au/library/thesaurus/introduction.html'
117 >discussion</a>), or a relatively lightweight processing involving
118 adding missing but mechanially inferrable relations.</p>
119
120 <p>Question: what should be the format of the master files?</p>
121
122 <p>Possible resolution 1: nothing mandated in the document -- the
123 format of the master file should be whatever is most convenient, as
124 long as the generated and distributed files are valid SKOS. [This
125 says: there is no need for the IVOA to specify this, as it's purely
126 private to the vocabulary maintainers]</p>
127
128 <p>Possible resolution 2: SKOS, in Turtle notation, possibly requiring
129 some post-processing to add omitted-but-inferrable relations. This is
130 easy to read and write, and it is simple enough that it would be
131 feasible to create from scratch a parser for the relevant subset of
132 it, if that were somehow necessary. [This says: what we're
133 distributing -- SKOS -- might as well be the format we edit, so we
134 mandate that, for the sake of simplicity]</p>
135
136 <p>Possible resolution 3: some more fundamental no-punctuation format,
137 such as that for the Lexicon program. [This says: we want to be
138 <em>completely</em> technology-agnostic, and even SKOS is too hard to
139 parse, post-apocalypse]</p>
140
141 <p><strong>Provisional resolution:</strong> option (1) above – nothing
142 mandated. Only the distribution format is to be specified (no
143 objections on the list).</p>
144
145 <p>Discussion (such as it was):
146 <a href='http://www.ivoa.net/forum/semantics/0802/0670.htm' >2008 Feb 4</a>
147 (+ thread).
148 </p>
149 <!--
150 <p>No 2 seems the best balance between manageability and long-term
151 maintainability.</p>
152 -->
153
154 </div>
155
156 <div class='section-nonum' id='distformat-2'>
157 <p class='title'>[distformat-2] Format of the distributed vocabularies</p>
158
159 <p>Question: in which format should vocabularies be distributed?</p>
160
161 <p>Possible resolution 1: the standard simply mandates that they be
162 distributed in at least one well-known RDF format (which means either RDF/XML
163 or Turtle, which is equivalent to N3 for this purpose). This implies that an
164 RDF parser will, realistically, be required in order to process the
165 vocabulary files.</p>
166
167 <p>Possible resolution 2: the standard requires them to be distributed
168 in a format which is parseable as RDF, but which is also regular
169 enough that it's usefully interpretable as ‘normal’ XML.</p>
170
171 <p><strong>Provisional resolution:</strong> option (1) above – distribution
172 in any RDF serialisation. More rationale to be added to the document.</p>
173
174 <p>Discussion:
175 <a href='http://www.ivoa.net/forum/semantics/0801/0644.htm' >2008 Jan 21</a>,
176 <a href='http://www.ivoa.net/forum/semantics/0801/0647.htm' >28</a> (+ thread),
177 <a href='http://www.ivoa.net/forum/semantics/0802/0674.htm' >2008 Feb 4</a>.
178 </p>
179
180 </div>
181
182 <div class='section-nonum' id='versioning-3'>
183 <p class='title'>[versioning-3] Identifying vocabulary versions</p>
184
185 <p>Question: do vocabulary users refer to a concept URI with an explicit
186 version, or to a constant URI which always refers to the latest version?</p>
187
188 <p>Possible resolution 1: users always refer to the same concept URI,
189 as for example in <code>http://myvocab.org/myvocab#mytoken</code>, and
190 this refers, either by redirection or server-internal URI rewriting,
191 to the latest version of the vocabulary. The Dublin Core metadata set
192 at <span class='url'>http://purl.org/dc/terms/</span> does this <span
193 class='cite'>std:dublincore</span>.</p>
194
195 <p>Possible resolution 2: users refer to a concept URI without a
196 version; this URL returns a vocabularly with a versioned namespace
197 (this can probably be excluded, since it violates the good practice of
198 having a namespace be retrievable at its own URL).</p>
199
200 <p>Possible resolution 3: users will refer to concepts which have a
201 version explicit within the namespace, as for example in
202 <code>http://myvocab.org/myvocab-v1.1#mytoken</code> (the precise
203 location of the version number or date in the URI is arguably a
204 distribution/maintainance detail).</p>
205
206
207
208 <p>References: see <span class='cite'>berrueta08</span>,
209 <span class='cite'>sauermann07</span>.</p>
210
211 <p>Discussion:
212 <a href='http://www.ivoa.net/forum/semantics/0801/0644.htm' >2008 Jan 21</a>,
213 <a href='http://www.ivoa.net/forum/semantics/0801/0648.htm' >28</a>
214 (+ threads),
215 <a href='http://www.ivoa.net/forum/semantics/0801/0660.htm' >31</a>,
216 <a href='http://www.ivoa.net/forum/semantics/0802/0678.htm' >2008 Feb 4</a>
217 </p>
218
219 </div>
220
221 <div class='section-nonum' id='maintenance-4'>
222 <p class='title'>[maintenance-4] Who maintains vocabularies?</p>
223
224 <p>Question: By whom, and by what process, are vocabularies maintained?</p>
225
226 <p>This is a different issue from <span
227 class='xref'>versioning-3</span>, since that is concerned with how the
228 versions are identified, whereas this is concerned with who it is
229 who manages the changes which are necessary as a vocabulary evolves.</p>
230
231 <p>Possible resolution 1: the vocabularies in the standardised
232 document are regarded purely as examples, with no normative force and
233 no specified maintenance process.</p>
234
235 <p>Possible resolution 2: the document's vocabularies are normative,
236 and the document should define a maintenance process, possibly
237 modelled on the UCD process <span class='cite' >std:ucdmaint</span>.</p>
238
239 <p>Possible resolution 3: the document's vocabularies are normative,
240 but not claimed to be more than merely adequate. They will not be
241 developed as part of this standard's evolution, but instead be
242 maintained by other interest groups, either within or outwith the IVOA
243 process.</p>
244
245 <p>Are there minimal standards of curation which conforming
246 vocabularies must abide by? For example, need we require vocabulary
247 maintainers to use the <code>&lt;skos:changeNote&gt;</code>
248 mechanisms, or just rely on their good sense?</p>
249
250 <p>Discussion:
251 <a href='http://www.ivoa.net/forum/semantics/0801/0665.htm' >2008 Jan 31</a>
252 </p>
253
254 </div>
255
256 <div class='section-nonum' id='vocabset-5'>
257 <p class='title'>[vocabset-5] What vocabularies are included in the standard?</p>
258
259 <p>Irrespective of the resolution to issue <span
260 class='xref'>maintenance-4</span>, there will be a set of vocabularies
261 included in the document, either as samples, or as an initial
262 specification. Question: What should this set contain?</p>
263
264 <p>There are six vocabularies which have been associated with the
265 draft standardisation process, namely</p>
266
267 <ul>
268 <li>the A&amp;A journal keyword list, the IVOA AOIM list, and the 1993
269 IAU thesaurus, whose inclusion is as far as I can see completely
270 uncontroversial;</li>
271 <li>an IVOA Thesaurus based on the IAU-93, which may or may not be in
272 this standard depending on whether people would prefer a completely
273 separate process to develop it;</li>
274 <li>a UCD1+ vocabulary (though this deals with a different set of
275 concepts – namely data types – from the other vocabularies and might
276 arguably connect poorly to them); and</li>
277 <li>a SKOS version of the list of constellations, which is very
278 simple, and which might reasonably find a home in this standard on
279 that ground alone.</li>
280 </ul>
281 <p>In addition, there are multiple informal keyword lists associated
282 with the VOEvent arena (see Roy's message and Rob's). These haven't
283 been SKOSified at all, and Rick's excellent suggestion is that these
284 be left as homework for the VOEvent group.</p>
285
286 <p>Discussion:
287 <a href='http://www.ivoa.net/forum/semantics/0801/0665.htm' >2008 Jan 31</a>,
288 <a href='http://www.ivoa.net/forum/semantics/0802/0682.htm' >2008 Feb 4</a>,
289 <a href='http://www.ivoa.net/forum/voevent/0802/0654.htm' >2008 Feb 4
290 (VOEvent list)</a>,
291 <a href='http://www.ivoa.net/forum/semantics/0802/0711.htm' >7</a>;
292 <a href='http://www.ivoa.net/twiki/bin/view/IVOA/VocabulariesWorkingArea'
293 >wiki page</a>.
294 </p>
295
296 </div>
297
298 </div>
299
300 <div class='appendices'>
301 <div class='section-nonum' id='bibliography'>
302 <p class='title'>Bibliography</p>
303 <?bibliography rm-refs ?>
304 </div>
305 </div>
306
307 </body>
308 </html>

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