Merge pull request #26 from gmantele/issue-16-udf-catalogue

Add a note about the the UDF catalogue

ADQL.tex

@@ -1475,6 +1475,18 @@ \subsubsection{Coordsys}
 clients are advised to pass an empty string here. Future versions of this
 specification may remove this parameter from the listed functions.
 
+This coordinate system argument was originally intended to carry information on
+a reference system or other coordinate system metadata. This was helpful in
+order to deal with data specified in different coordinate systems while
+performing geometric operations. It was up to the ADQL service to perform
+the appropriate conversion to make these operations possible. Now this argument
+is deprecated and will later be removed, the users should explicitly ask for
+such conversion. If this behavior is desired, the ADQL implementers have to
+allow it through User Defined Functions. Then, it is recommended to define them
+as declared in the \CatalogueUDF.
+% Catalogue of {ADQL} User Defined Functions - Endorsed Note 1.0+
+% http://www.ivoa.net/documents/udf-catalogue/index.html
+
 \subsubsection{Predicate functions}
 \label{sec:functions.geom.predicate}
 
@@ -2455,6 +2467,12 @@ \subsubsection{Overview}
     ivo_string_agg()
 \end{verbatim}
 
+In order to avoid different signatures for the same functions, it is recommended
+that ADQL implementers follow as much as possible the User Defined Function
+signatures listed in the \CatalogueUDF.
+% Catalogue of {ADQL} User Defined Functions - Endorsed Note 1.0+
+% http://www.ivoa.net/documents/udf-catalogue/index.html
+
 %If metadata on a user defined function is available, this should be used. For
 %example function names and cardinality of arguments should be checked against
 %metadata where available.

ivoa-cite.tex

@@ -30,6 +30,8 @@
 \newcommand{\STCSSpec}    {\IvoaCite{stcsspec}    {std:STCS}            {STC-S specification}}
 \newcommand{\ObsCoreSpec} {\IvoaCite{obscorespec} {2017ivoa.spec.0509L} {ObsCore specification}}
 
+\newcommand{\CatalogueUDF} {\IvoaCite{udfcat}     {2021ivoa.spec.0310C} {Catalogue of ADQL User Defined Functions}}
+
 %
 % Useful macros for referring to figures, sections and appendices in a consistent style.
 \newcommand{\FigureRef}[1]{Figure \ref{#1}\xspace}