%\section{Use Cases}
% alberto's
The ability to discover data of a certain kind (\emph{images, spectra, cubes, etc.}) according to some scientific criteria
(\emph{e.g., a given sky position, spectral coverage including spectral line X, spatial resolution better than Y, resolving power greater than Z})
is central to archival Astronomy. A special Take Up Committee of the IVOA was formed in 2009 to stimulate the IVOA work
in the area of a catalogue-based data access layer that allows astronomers to easily query and access scientific data.
Such committee came up with a list of data discovery use cases expressed as a set of constraints on selected scientific
parameters to be met by the datasets of interest. The full list of use cases is herein included.
% Those use cases are listed in appendix \ref{app-use-cases}.
% A specific (TBW) tracebility matrix section (see \ref{tracematrix} shows which use cases are actually coveredby this ObsTAP standard, and which ones would require additional work by the IVOA working groups, to fully accomplishthe established goal.
% end of alberto's
\subsection{Use Cases 1:	Discover imaging data of interest}
Use case 1.1:	Show me a list of all data that satisfies
\begin{enumerate}
\item [i]	DataType=any
\item [ii]	Energy includes 5 keV
\item [iii]	RA includes 16.00
\item [iv]	DEC includes +10
\item [v]	Exposure time $>  10$ ks
\end{enumerate}
%
Use case 1.2:	Let me input a list of RA and DEC coordinates and show me spatially coincident data that satisfies
\begin{enumerate}
\item [i]	Imaging or spectroscopy data
\item [ii]	Includes one or more of the RA,DEC values in the list (LIST=SERVICE REQ)
\item [iii]	Includes both a wavelength in the range 5000-900 angstroms AND an X-ray image (AND=SERVREQ)
\end{enumerate}
%
Use case 1.3:	Show me a list of all data that satisfies
\begin{enumerate}
\item [i]	DataType=Image
\item [ii]	Spatial resolution better than 0.3 arcseconds
\item [iii]	Filter = J or H or K
\item [iv]	RA between 16 hours and 17 hours
\item [v]	DEC between 10 degrees and 11 degrees
\end{enumerate}
%
Use case 1.4:	Show me a list of all data that satisfies
\begin{enumerate}
\item [i]	DataType=Image
\item [ii]	Wavelength=V or I or Z
\item [iii]	Spatial Resolution $< 0.7$ arcseconds FWHM
\item [iv]	Exposure Time $> 1000$ seconds
\item [v]	Data Quality: Fully Calibrated
\end{enumerate}
%
Use case 1.5:	Show me all data that satisfies
\begin{enumerate}
\item [i]	DataType=IFU
\item [ii]	DataQuality: Fully Calibrated
\item [iii]	ObjectClass=quasar  (SERVIC REQ + NEEDS ANOTHER SERVICE (CATALOGUE)
\item [iv]	Redshift $> 3.$
\item [v]	Radioflux $> 1$ mJy
\end{enumerate}
%
Use case 1.6:	For an input list of RA,DEC, Mean Julian Date, show me all data that satisfies (LIST=SERVREQ)
\begin{enumerate}
\item [i]	DataType=imaging
\item [ii]	RA,DEC include the value and the list and Observation date is within 1 day of the MJD value
\end{enumerate}



\subsection{Use Cases 2:	Discover spectral data of interest}

Use case 2.1:	Show me a list of all data that satisfies
\begin{enumerate}
\item [i]	DataType=Spectrum
\item [ii]	Energy  spans 1 to 5 keV
\item [iii]	Total counts in spectrum $> 100$
\item [iv]	Exposure time $>  10000$ seconds
\item [v]	Data Quality: Fully Calibrated
\end{enumerate}
%
Use case 2.2:	Show me a list of all data that satisfies
\begin{enumerate}
\item [i]	DataType=Spectrum
\item [ii]	Wavelength includes 6500 angstroms
\item [iii]	Spectral Resolution better than 15 angstroms
\item [iv]	Spatial Resolution better than 2 arcseconds FWHM
\item [v]	Exposure Time $> 3600$ seconds
\item [vi]	Data Quality = Any
\end{enumerate}
%
Use case 2.3:	Show me a list of all data that satisfies
\begin{enumerate}
\item [i]	Emission line width $H_{\alpha} > 2000$ km/s FWHM (SERVICEREQ+NEEDS OTHER SERVICE)
\item [ii]	$H_{\alpha}/H_{\beta} > 3.5$
\end{enumerate}

\subsection{Use Cases 3:	Discover data cubes of interest}

Use case 3.1:	Show me a list of data
\begin{enumerate}
\item [i]	DataType=cube (IFU spectroscopy?)
\item [ii]	RA,DEC includes value RA1,DEC1
\item [iii]	Field size $> 100$ square arcseconds
\item [iv]	DataSensitivity = deep
\item [v]	Spectral resolution better than 5 angstroms FWHM
\end{enumerate}
%
%
Use case 3.2:	Show me a list of all data that satisfies
\begin{enumerate}
\item [i]	DataType=Cube with 3 dimensions
\item [ii]	Axes includes Velocity
\item [iii]	Axes includes RA
\item [iv]	Axes includes DEC
\item [v]	Velocity Resolution better than 50 km/s
\item [vi]	RA includes 16.000
\item [vii]	Dec includes +41.000
\end{enumerate}
%
Use case 3.3:	Show me a list of all data that satisfies
\begin{enumerate}
\item [i]	DataType=cube
\item [ii]	RA includes 16.00
\item [iii]	Dec includes +41.00
\item [iv]	Wavelength includes 6500 angstroms
\item [v]	Wavelength includes 4000 angstroms
\item [vi]	Spectral resolution better than 5 angstroms
\item [vii]	Exposure time more than 3600 seconds
\item [viii]	Data Quality: Fully Calibrated
\end{enumerate}
%
Use case 3.4:Show me a list of all data that satisfies
\begin{enumerate}
\item [i] DataType=Cube with 3 dimensions
\item [ii] Axes includes FREQ
\item [iii] Axes includes RA
\item [iv] Axes includes DEC
\item [v] Velocity Resolution better than 1 km/s
\item [vi] RA includes  83.835000
\item [vii] Dec includes -5.014722
\item [viii] Rest Frequency = 345.795990 GHz
\item [ix] VLSRK in the range [6.0, 10.0]
\end{enumerate}
%
Use case 3.5:Show me a list of all data that satisfies
\begin{enumerate}
\item [i] DataType=Cube with 3 dimensions
\item [ii] Axes includes FREQ
\item [iii] Axes includes RA with $>100$ pixels
\item [iv] Axes includes DEC with $>100$ pixels
\item [v] Frequency extent $> 500$ MHz
\item [vi] Rest Frequency = 345.795990 GHz appears in band
\item [vii] The redshift is not specified, but should default to $z_{source}$ for the
target.
\end{enumerate}
%
Use case 3.6:Show me a list of all data that satisfies
\begin{enumerate}
\item [i] DataType=Cube with 3 dimensions
\item [ii] Axes includes FREQ
\item [iii] Axes includes RA
\item [iv] Axes includes DEC
\item [v] Frequency resolution $< 10$ MHz
\item [vi] Rest Frequency = 337.2966 GHz appears in band
\item [vii] Any observation that could have detected a line at this rest frequency
from any target, using the nominal redshift for the target.
\end{enumerate}
%
Use case 3.7:Show me a list of all data that satisfies
\begin{enumerate}
\item [i] DataType=Cube with 3 dimensions
\item [ii] Axes includes FREQ
\item [iii] Axes includes RA
\item [iv] Axes includes DEC
\item [v] Frequency resolution $< 10$ MHz
\item [vi] Rest Frequency in (213.36053, 256.0278, 298.6908925,
       341.350826, 384.0066819, 426.6579505, 469.3041221,
       511.944687, 554.5791355) GHz appears in band
\item [vii] Any observation that could have detected HCS+ (list of transition rest frequencies given above) from any target, using the nominal redshift for the target.
\end{enumerate}
%
Use case 3.8:Show me a list of all data that satisfies
\begin{enumerate}
\item [i] DataType=Cube with 4 dimensions
\item [ii] Axes includes FREQ
\item [iii] Axes includes RA with $>100$ pixels
\item [iv] Axes includes DEC with $>100$ pixels
\item [v] Axes includes STOKES
\item [vi] Frequency resolution $< 1$ MHz
\item [vii] Rest Frequency = 345.795990 GHz appears in band
\end{enumerate}
%
Use case 3.9:  Looking for moving targets
\begin{enumerate}
\item [i] Show me the names of all the objects that have moving coordinates (i.e. no RA,Dec position).
\end{enumerate}


\subsection{Use Cases 4:	Discover time series of interest}

Use case 4.1:	Show me a list of all data that satisfies
\begin{enumerate}
\item [i]	DataType=TimeSeries
\item [ii]	RA includes 16.00 hours
\item [iii]	DEC includes +41.00
\item [iv]	Time resolution better than 1 minute
\item [v]	Time interval (start of series to end of series) $> 1$ week
\item [vi]	Observation data before June 10, 2008
\item [vii]	Observation data after June 10, 2007
\end{enumerate}



\subsection{Use Cases 5:	Discover general data of interest}

%
% DIMSISSED on the basis that this is identical to use case 3.3.
% Changing numbering scheme of subsequent use cases accordingly.
%
%Use case 5.1:	Show me a list of all data that satisfies
%\begin{enumerate}
%\item [i]	DataType=any
%\item [ii]	RA includes 16.00
%\item [iii]	Dec includes +41.00
%\item [iv]	Wavelength includes 6500 angstroms
%\item [v]	Wavelength includes 4000 angstroms
%\item [vi]	Spectral resolution better than 5 angstroms
%\item [vii]	Exposure time more than 3600 seconds
%\item [viii]	Data Quality: Fully Calibrated
%\end{enumerate}
%


Use case 5.1:	Show me a list of all data that satisfies
\begin{enumerate}
\item [i]	Optical imaging
\item [ii]	In the M81 group
\item [iii]	With area greater than 0.5 degress square
\item [iv]	With sensitivity $> 10*\sigma$ for point source m=25
\item [v]	I also want X-ray data with cutouts 5 arcmin on a side of all the detected galaxies
\item [vi]	I also want Radio data cutouts 5 arcmin on a side around detected galaxies
\end{enumerate}
%
Use case 5.2:	Show me a list of all data that satisfies
\begin{enumerate}
\item [i]	DataType=Imaging or Spectroscopy
\item [ii]	RA includes 16.00 hours
\item [iii]	DEC includes +41.00 degress
\item [iv]	SDSS images and spectra AND CFHTLS images and spectra
\end{enumerate}
%
Use case 5.3:	In Virgo cluster show me imaging and X-ray data for all galaxies that are cluster members and have $B < 21$

\subsection{Use Cases 6: Others}
\begin{enumerate}

\item [6.1] Given COSMOS (or other survey) X-Ray source catalogue give me all the sources with $photoZ > X$, and spiral galaxy counterpart and produce radio - to -X-ray SEDs \\
Comment : Requires source/object catalogues to drive data query (for SED info which may be catalogue or data)

\item [6.2] Given a list of Abell clusters, give me all their Chandra images with $texp>X$, after I select regions occupied by the diffuse emission, give me all the Chandra point sources in these regions, and find their redshift (I want to find background quasars because I am interested in lensing and I have no idea where to go to find z). For the quasars, give me high res ($<0.5"$) optical and radio images, and build SEDs \\
Comment: Requires source/object catalogues and interactive image interactions (applications/interfaces), further query, and more catalogues to drive data query.

\item [6.3] Find me all the variable Chandra sources with optical counterpart and redshift. If redshift is not available, give me an SED to compare with source templates (I also would like to run a tool or obtain a library of such templates from a theory database, which I expect the VO to provide). My aim is to separate stars from variable quasars.\\
Comment: Pretty complicated, including templates and theory as well as catalogues.
\end{enumerate}
 


