Request for Modification for the UCD vocabulary towards UCDList v1.4This page summarizes the steps for Modifications and Updates proposed in The UCD Maintenance workink draft . The second (on going) iteration for the Request for modifications of UCD terms is summarized in the following content. These terms are submitted for evaluation to the UCD science committee (see details in the Maintenance Specification document).UCDList v1.4 Request For Modifications, from May 2018 to Oct 2018Proposed UCD: stat.histogramUse Case: A column contains not a single value but a distribution-like entity. For an example, run a query likeselect gavo_histogram(phot_g_mean_mag, 5, 15, 10) as dist, round(100/parallax) as bin from tgas.main where parallax>5 group by binon the TAP service http://dc.g-vo.org/tap and inspect the dist column. Proposed Solution: a primary-only atom stat.histogram would work for this. In the example in the use case, the service could assign a UCD stat.distribution;pos.parallax to the dist column. Hence, we'd add a new line to the UCD list: P|stat.histogram | An array-like object with counts or ratios in bins A footnote like "This also includes simple nonparametric distributions" or similar would be appreciated. -- MarkusDemleitner - 2018-05-09 DiscussionThe column dist from the example certainly cannot be annotated as pos.parallax, and while there is stat.likelihood, there is no indication that this is intended to cover collection of likelihoods. I argue the UCD system should allow a plausible annotation of the dist column. If so, it appears we need some new term. This new term should, I think, cover simple binned aggregations as well as nonparametric distributions (in the sense of \sum_{x\in\Omega} P(x)=1) in order to have sufficient generality. Hence, I'd avoid stat.distribution, which would imply normalisation. Also, stat.distribution (or something like that) might, some day, be useful to annotate a different thing that this would not cover: columns containing distributions in the sense of some representation of "a gaussian with mu=3 and sigma=0.3" or "a poisson distribution with lambda=0.2".Answer/discussionThe discussion started on the semantics mailing list . see the starting point for this discussion here The proposed term is considering an array element instead of a single value , usually considered for the quantity tagged by a UCD. Note that the semantic tag does not describe any property of the array except its statistical definition of histogram.DecisionExamine more use cases where this UCD could be combined to check the P or Q status before approving addition | ||||||||
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> > | Being able to tell that a column contains a histogram could be useful. However, the use of the UCD only is not sufficient to describe that column. We suggest that the histogram column is connected to a <GROUP ... /> through a ref attribute. The GROUP should define the binsize, the number of bins and the lower / upper bounds of the histogram, with units. Example: | |||||||
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> > | [...] <GROUP ID='histogram'> <PARAM name='lower_bound' value=5 unit='' ucd='phot.mag;em.opt;stat;mean'/> <PARAM name='upper_bound' value=15 unit='' ucd='phot.mag;em.opt;stat;mean'/> <PARAM name='bin_count' value=10 unit='' ucd='meta.number'/> <PARAM name='bin_size' value=1 unit='' ucd=''/> </GROUP> [...] <FIELD ID='dist' datatype='int', ucd='stat.histogram;phot.mag;em.opt;stat;mean' ref='histogram' arraysize='*'/> [...] | |||||||
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> > | The result of the proposed query can't be used out of context, since the histogram properties are not described. This is beyond the scope of Semantics/UCD, but this shows that we have to be cautious and may be propose a Note on how to deal with histograms in VOTable columns. -- BaptisteCecconi - 2020-02-06 | |||||||
Previous iteration for the Request for modifications of UCD terms is summarized in the following page. ( click the link)
UCDList v1.3 - from May 2017 to Feb 2018Pending concepts considered in previous iteration waiting for more examples and use-case updateConcept: shape of planetary objects. | ||||||||
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< < | pos. Euler.Angle | |||||||
> > | pos.rotation | |||||||
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< < | pos.rotation | |||||||
> > | pos.Euler.Angle | |||||||
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< < | posEuler.Angle | |||||||
Concept : orbital parameters
Concept : 3D rotation parameters
-- MireilleLouys - 2020-02-03
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