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Schema description should include units. #119

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ijiraq opened this issue Sep 22, 2019 · 7 comments
Closed

Schema description should include units. #119

ijiraq opened this issue Sep 22, 2019 · 7 comments

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@ijiraq
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ijiraq commented Sep 22, 2019 •
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The schema descriptions that appear in the TAP services should tell the user what UNITs quantities in the table are expressed in. e.g. Plane.energy_bounds_lower is described as:
'lower bound on energy axis (barycentric wavelength)' which is helpful, but without knowing what units those are (nm?) the user is left to guess.

One might thing that just declaring the entire table as following some convention (cgi? mks?) would be sufficient) but reminding the user with good column descriptions would be more friendly.
@pdowler
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pdowler commented Nov 28, 2019

The tap_schema.columns table has a column named unit that conveys the units for all columns where that is applicable.

We don't include units in the description because redundancy is the first step to inconsistency :-)

@ijiraq
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ijiraq commented Nov 29, 2019 via email

@pdowler
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pdowler commented Jan 9, 2020

On the above cadc-tap output, the "Type" column there is useless to normal users as it is not a type in the normal sense. That is the VO-DML ID so a reference to a specific field in the data model. The schema + table + column name has the same info as the model ID with a syntactic mapping to make valid database names.

It would be much better to tell users the datatype,arraysize,xtype from the tap_schema -- those 3 together are the VOTable and TAP "datatype".

@pdowler
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pdowler commented Jan 9, 2020

As for targetPosition_cval1 that is the name of the field in the Point class so the correct column name. It is cval (coordinate value) and not crval (coordinate reference value).

The units are specified in a "profile" and not in the model directly. We currently have the http://www.opencadc.org/caom2/interoperable-profile.html

The TAP service uses the interoperable profile and the units are available in the "unit" column of the tap_schema, so the above table info output should include that column along with the more useful datatype info.

@pdowler pdowler mentioned this issue Jan 9, 2020
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@ijiraq
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ijiraq commented Jan 13, 2020

@andamian : Do we have agreement then that we modify the information that cadc-tap provides along the lines that @pdowler suggests? Sounds right to me.

@pdowler : Separate question about the 'cval1' and 'cval2' colums. Are they well described (ie, what coordinate system them reference) in those other information provided in the tap_schema?

@andamian
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@ijiraq - easy-peasy - or it seems like. This can be closed as #130 is tracking it now.

@ijiraq
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ijiraq commented Jan 14, 2020

I think we don't close this until opencadc/cadctools#130 has been resolved. This issue contains the information about what is being asked for.

Still waiting to learn if the cval1/2 description is useful in tap_schema.

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@ijiraq @andamian @pdowler