\def\attrx#1{{\em\fg{DarkRed}#1}}
\begin{tabular}{cccccc}      %%%  6 columns in main table

%%% Row 1
\begin{tabular}{@{}c@{}}	%%% Start cell r1c1
	\begin{tabular}{|l|}\hline
		\multicolumn{1}{|c|}{\elem{VOTABLE}}\\
		\multicolumn{1}{|c|}{{\em(\Aref{elem:VOTABLE}{definition})}}\\ \hline{}
		\attr{ID}\\		%%% what could be the usage of ID here ?
		\attr{version}\\
	\hline\end{tabular}
\end{tabular}			%%% End cell r1c1

&
\begin{tabular}{@{}c@{}}	%%% Start cell r1c2
	\begin{tabular}{|l|}\hline
		\multicolumn{1}{|c|}{\elem{COOSYS}}\\
		\multicolumn{1}{|c|}{{\em(\Aref{elem:COOSYS}{definition})}}\\ \hline{}
		\requiredattr{ID}\\
		\attr{equinox}\\
		\attr{epoch}\\
		\attr{system}\\
	\hline\end{tabular}
	\\ \\
	\begin{tabular}{|l|}\hline
		\multicolumn{1}{|c|}{\elem{TIMESYS}}\\
		\multicolumn{1}{|c|}{{\em(\Aref{elem:TIMESYS}{definition})}}\\ \hline{}
		\requiredattr{ID}\\
		\attr{timeorigin}\\
		\requiredattr{timescale}\\
		\requiredattr{refposition}\\
	\hline\end{tabular}
\end{tabular}			%%% End cell r1c2

&
\begin{tabular}{@{}c@{}}	%%% Start cell r1c3
	\begin{tabular}{|l|}\hline
		\multicolumn{1}{|c|}{\elem{INFO}}\\
		\multicolumn{1}{|c|}{{\em(\Aref{elem:INFO}{definition})}}\\ \hline{}
		\attr{ID}\\
		\requiredattr{name}\\
		\requiredattr{value}\\
		\attr{xtype}\\
		\attr{ref}\\
		\attr{unit}\\
		\attr{ucd}\\
		\attr{utype}\\
	\hline\end{tabular}
\end{tabular}			%%% End cell r1c3

&
\begin{tabular}{@{}c@{}}	%%% Start cell r1c4
\begin{tabular}{|l|}\hline
	\multicolumn{1}{|c|}{\elem{GROUP}}\\
	\multicolumn{1}{|c|}{{\em(\Aref{elem:GROUP}{definition})}}\\ \hline{}
	\attr{ID}\\
	\attr{name}\\
	\attr{ref}\\
	\attr{ucd}\\
	\attr{utype}\\
	\hline\end{tabular}
\\ \\
\begin{tabular}{|l|}\hline
	\multicolumn{1}{|c|}{\elem{RESOURCE}}\\
	\multicolumn{1}{|c|}{{\em(\Aref{elem:RESOURCE}{definition})}}\\ \hline{}
	\attr{ID}\\
	\attr{name}\\
	\attr{type}\\
	\attr{utype}\\
	\hline\end{tabular}
\end{tabular}			%%% End cell r1c3

&
\begin{tabular}{@{}c@{}}	%%% Start cell r1c5
	\begin{tabular}{|l|}\hline
		\multicolumn{1}{|c|}{\elem{PARAM}}\\
		\multicolumn{1}{|c|}{{\em(\Aref{elem:PARAM}{definition})}}\\ \hline{}
		\attr{ID}\\
		\attr{unit}\\
		\requiredattr{datatype}\\
		\attr{precision}\\
		\attr{width}\\
		\attr{xtype}\\
		\attr{ref}\\
		\requiredattr{name}\\
		\attr{ucd}\\
		\attr{utype}\\
		\attr{arraysize}\\
		\requiredattr{value}\\
	\hline\end{tabular}
\end{tabular}			%%% End cell r1c4

&
\begin{tabular}{@{}c@{}}	%%% Start cell r1c6
	\begin{tabular}{|l|}\hline
		\multicolumn{1}{|c|}{\elem{FIELD}}\\
		\multicolumn{1}{|c|}{{\em(\Aref{elem:FIELD}{definition})}}\\ \hline{}
		\attr{ID}\\
		\attr{unit}\\
		\requiredattr{datatype}\\
		\attr{precision}\\
		\attr{width}\\
		\attr{xtype}\\
		\attr{ref}\\
		\requiredattr{name}\\
		\attr{ucd}\\
		\attr{utype}\\
		\attr{arraysize}\\
		\attrx{type}\\
	\hline\end{tabular}
\end{tabular}			%%% End cell r1c5

\\ \\
\\ \\

%%% Row 2
\begin{tabular}{@{}c@{}}	%%% Start cell r2c1
	\begin{tabular}{|l|}\hline
		\multicolumn{1}{|c|}{\elem{TABLE}}\\
		\multicolumn{1}{|c|}{{\em(\Aref{elem:TABLE}{definition})}}\\ \hline{}
		\attr{ID}\\
		\attr{name}\\
		\attr{ucd}\\
		\attr{utype}\\
		\attr{ref}\\
		\attr{nrows}\\
	\hline\end{tabular}
\end{tabular}			%%% End cell r2c1

&
\begin{tabular}{@{}c@{}}	%%% Start cell r2c2
\begin{tabular}{|l|}\hline
	\multicolumn{1}{|c|}{\elem{FIELDref}}\\
	\multicolumn{1}{|c|}{{\em(\Aref{elem:FIELDref}{definition})}}\\ 
	\hline{}
	\requiredattr{ref}\\
	\attr{ucd}\\
	\attr{utype}\\
	\hline\end{tabular}
\\ \\
\begin{tabular}{|l|}\hline
	\multicolumn{1}{|c|}{\elem{PARAMref}}\\
	\multicolumn{1}{|c|}{{\em(\Aref{elem:PARAMref}{definition})}}\\ 
	\hline{}
	\requiredattr{ref}\\
	\attr{ucd}\\
	\attr{utype}\\
	\hline\end{tabular}
\end{tabular}			%%% End cell r2c2

&
\begin{tabular}{@{}c@{}}	%%% Start cell r2c3
	\begin{tabular}{|l|}\hline
		\multicolumn{1}{|c|}{\elem{STREAM}}\\
		\multicolumn{1}{|c|}{{\em(\Aref{elem:STREAM}{definition})}}\\ \hline{}
		\attr{type}\\
		\attr{href}\\
		\attr{actuate}\\
		\attr{encoding}\\
		\attr{expires}\\
		\attr{rights}\\
	\hline\end{tabular}
\end{tabular}			%%% End cell r2c2

&
\begin{tabular}{@{}c@{}}	%%% Start cell r2c4
	\begin{tabular}{|l|}\hline
		\multicolumn{1}{|c|}{\elem{FITS}}\\
		\multicolumn{1}{|c|}{{\em(\Aref{elem:FITS}{definition})}}\\ \hline{}
		\attr{extnum}\\
	\hline\end{tabular}
	\\ \\
	\begin{tabular}{|l|}\hline
		\multicolumn{1}{|c|}{\elem{TR}}\\
		\multicolumn{1}{|c|}{{\em(\Aref{elem:TR}{definition})}}\\ \hline{}
		\attrx{ID}\\
	\hline\end{tabular}
	\\ \\
	\begin{tabular}{|l|}\hline
		\multicolumn{1}{|c|}{\elem{TD}}\\
		\multicolumn{1}{|c|}{{\em(\Aref{elem:TD}{definition})}}\\ \hline{}
		%\attr{ref}\\
		\attrx{encoding}\\
	\hline\end{tabular}
\end{tabular}			%%% End cell r2c3

&
\begin{tabular}{@{}c@{}}	%%% Start cell r2c5
	\begin{tabular}{|l|}\hline
		\multicolumn{1}{|c|}{\elem{MIN}}\\
		\multicolumn{1}{|c|}{{\em(\Aref{elem:MIN}{definition})}}\\ \hline{}
		\requiredattr{value}\\
		\attr{inclusive}\\
	\hline\end{tabular}
	\\ \\
	\begin{tabular}{|l|}\hline
		\multicolumn{1}{|c|}{\elem{MAX}}\\
		\multicolumn{1}{|c|}{{\em(\Aref{elem:MAX}{definition})}}\\ \hline{}
		\requiredattr{value}\\
		\attr{inclusive}\\
	\hline\end{tabular}
	\\ \\
	\begin{tabular}{|l|}\hline
		\multicolumn{1}{|c|}{\elem{OPTION}}\\
		\multicolumn{1}{|c|}{{\em(\Aref{elem:OPTION}{definition})}}\\ \hline{}
		\attr{name}\\
		\requiredattr{value}\\
	\hline\end{tabular}
\end{tabular}			%%% End cell r2c5

&
\begin{tabular}{@{}c@{}}	%%% Start cell r2c6
	\begin{tabular}{|l|}\hline
		\multicolumn{1}{|c|}{\elem{VALUES}}\\
		\multicolumn{1}{|c|}{{\em(\Aref{elem:VALUES}{definition})}}\\ \hline{}
		\attr{ID}\\
		\attr{type}\\
		\attr{null}\\
		\attr{ref}\\
		%\attr{invalid}\\
	\hline\end{tabular}
	\\ \\
	\begin{tabular}{|l|}\hline
		\multicolumn{1}{|c|}{\elem{LINK}}\\
		\multicolumn{1}{|c|}{{\em(\Aref{elem:LINK}{definition})}}\\ \hline{}
		\attr{ID}\\
		\attr{content-role}\\
		\attr{content-type}\\
		\attr{title}\\
		\attr{value}\\
		\attr{href}\\
		%\attr{gref}\\
		\attrx{action}\\
	\hline\end{tabular}
\end{tabular}			%%% End cell r2c6

\end{tabular}     %%%  End main table