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Merge pull request #41 from ivoa/obscore
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Obscore section rewording
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mservillat authored Nov 16, 2024
2 parents e4af419 + ab9297a commit 78da863
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19 changes: 10 additions & 9 deletions VOHE-Note.tex
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Expand Up @@ -915,10 +915,11 @@ \subsubsection{Usage of the mandatory terms in ObsCore}

%\todo[inline]{TODO: show a table with all reused terms , and provide an example}

Mandatory terms in ObsCore may be for example:
Terms in ObsCore may be filled in the following way for example, considering a \gls{CTAO} DL3 dataset:

\begin{itemize}
\item dataproduct\_subtype = DL3, maybe specific data format (\gls{VODF})
\item dataproduct_type = event
\item dataproduct\_subtype = DL3, maybe specific data format (e.g. \gls{VODF})
\item calib\_level = between 1 and 2
\item obs\_collection could contain many details : obs\_type (calib, science), obs\_mode (subarray
configuration), pointing\_mode, tracking\_type, event\_type, event\_cuts, analysis\_type…
Expand All @@ -933,33 +934,33 @@ \subsubsection{Usage of the mandatory terms in ObsCore}

\subsubsection{Metadata re-interpretation for the HE context}

\paragraph{observation\_id}
\paragraph{obs\_id}
In the current definition of ObsCore, the data product collects data from one or several observations. The same happens in \gls{HE} context.

\paragraph{access\_ref, access\_format}
The initial role of this metadata was to hold the access\_url allowing data access.
Depending on the packaging of the event bundle in one compact format (\gls{OGIP}, \gls{GADF}, tar ball, ...)
or as different files available independently in various urls, a datalink pointer can be used for accessing the various parts of \gls{IRF}s, background maps, etc.
or as different files available independently in various urls, a datalink pointer may be used for accessing the various parts of \gls{IRF}s, background maps, etc.
Then in such a case the value for access\_format should be "application/x-votable+xml;content=datalink". The format itself of the data file is then given by the datalink parameter "content-type".
See next section \ref{sec:datalink}.

\paragraph{o\_ucd}
For the even-list table, we can consider all measures stored in columns values have been observed .
The nature of items along time, position and energy axis are identifed in Obscore with ucd as 'time', 'pos.eq.*', 'em.*'
For the even-list table, we can consider that all measures stored in column values have been observed.
The nature of items along time, position and energy axis are identifed in Obscore with UCD as 'time', 'pos.eq.*', 'em.*'
and counted as t\_xel, s\_xel1, s\_xel2, em\_xel which correspond to the number of rows/events candidates observed.

The signal observed is the result of event counting and would be PHA (Pulse height amplitude at detector level) or a number of counts for photons or particles, or a flux, etc.., depending on the data calibration level considered.
ObsCore uses o\_ucd to characterise the nature of the measure.
Various UCDs are used for that: o\_ucd=phys.count, phot.count, phot.flux, etc. there is currently no UCD defined for a raw measure like PulseHeightAmplitude, but if needed this can be requested for addition in the UCDList vocabulary. See VEP-UCD-15\_pulseheight.txt proposed at \url{'https://voparis-gitlab.obspm.fr/vespa/ivoa-standards/semantics/vep-ucd/-/blob/master/'}.
Various UCDs are used for that: o\_ucd=phys.count, phot.count, phot.flux, etc. there is currently no UCD defined for a raw measure like PulseHeightAmplitude, but if needed this can be requested for addition in the UCDList vocabulary\footnote{See VEP-UCD-15\_pulseheight.txt proposed at \url{'https://voparis-gitlab.obspm.fr/vespa/ivoa-standards/semantics/vep-ucd/-/blob/master/'}}.

Note that these parameters vary between the dataset of calib\_level of 1 (Raw) to the a more advanced data products (calib\_level 2 or 3), which are filtered and rebinned from the original raw event-list.


\subsubsection{Proposed additions}
\subsubsection{Possible additions}

\paragraph{ev\_number}
The event-list contains a number of rows, representing detections candidates, that have no metadata keyword yet in Obscore.
We propose 'ev\_number' to record this.
We could propose 'ev\_number' to record this.
In fact the t\_xel, s\_xel1 and s\_xel2, em\_xel elements do not apply for an event-list in raw count as it has not been binned yet.

\paragraph{Adding MIME-type to access\_format table}
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