Merge branch 'master' into radec-decimal-and-ucds

ConeSearch.tex

@@ -144,7 +144,7 @@ \section{Service Interface Requirements}
 			not significant.
 		\item The baseURL and constraint list are concatenated
 			to form the query. 
-		\item The set of query constraints must include the
+		\item The set of query constraints MUST include the
 			following parameters, which are interpreted by the service with the
 			stated meaning: 
 			\begin{description}
@@ -154,13 +154,25 @@ \section{Service Interface Requirements}
 				\item[\textbf{DEC}] a declination
 					in the ICRS coordinate system for the positon of the center of the cone
 					to search, given in decimal degrees.
-				\item[\textbf{SR}] the radius of
-					the cone to search, given in decimal degrees.
+				\item[\textbf{SR}] the radius of the cone to search, given in decimal degrees.
+					If set to zero (SR=0) it should not return an error condition because the
+					request might describe an interest in retrieving only the metadata structure
+					of the service's response (i.e. discovery of the FIELDS delivered by the service).
+					This is similar to setting MAXREC=0, i.e. a service metadata request as prescribed
+					by DALI\footnote{SR=0 is kept in this version of this specification for back
+					compatibility. It is suggested to prefer the usage of MAXREC to enable metadata
+					discovery}\citep{2017ivoa.spec.0517D}.
 			\end{description}
 			\begin{bigdescription}
 				\item[Example]
 					\url{http://mycone.org/cgi-bin/search?RA=180.567&DEC=-30.45&SR=0.0125}
 			\end{bigdescription}
+		\item As defined by DALI a service SHOULD also understand the following parameter:
+			\begin{description}
+				\item[\textbf{MAXREC}] to let the client limit the number of records returned
+					or require a service metadata response. Its usage is encouraged and preferred
+					to the SR=0 solution for metadata discovery.
+			\end{description}
 		\item The query MAY contain the optional parameter,
 			\textbf{VERB}, whose value is an integer--either 1, 2, or 3--indicating
 			verbosity which determines how many columns are to be returned in the
@@ -209,8 +221,9 @@ \section{Service Interface Requirements}
 		The VOTable MUST comply with these conditions:
 
 		\begin{itemize}
-			\item There must be a single RESOURCE in the VOTable,
-				and that contains a single TABLE.
+			\item There must be a single RESOURCE with \texttt{type=''results''} in the VOTable,
+				and that RESOURCE must contain a single TABLE. Additional RESOURCE(s) are
+				allowed to enable, e.g., DataLink service descriptors.
 			\item The TABLE must have FIELDS where
 				the following UCD values have been set. There must only be one FIELD
 				with each of these UCDs:
@@ -323,11 +336,7 @@ \section{Service Interface Requirements}
 		Southern hemisphere and the catalog coverage is in the Northern
 		hemisphere. This type of query is different from an error return; it
 		should return a VOTable as described above, with metadata, but no data
-		records. In particular, a zero value of Search Radius should not return
-		an error condition. This is because an application may be more
-		interested in the metadata than the data, and send a fixed query (for
-		example RA=0\&DEC=90\&SR=0) simply to discover the fields delivered by
-		the service.
+		records.
 \end{enumerate}
 
 \section{The Resource Profile}