\begin{hetcasl}

\SPEC \=\SIdIndex{A} \= \Ax{=}\\
\>\SORTS \=\Id{A}, \Id{B}, \Id{C} \Ax{<} \Id{T}\\
\>\PREDS \=\Id{R1} : \Id{A} \Ax{\times}  \Id{B};\\
\>\> \Id{R2} : \Id{B} \Ax{\times}  \Id{C};\\
\>\> \Id{R3} : \Id{C} \Ax{\times}  \Id{T}\\
\END\\
\\
\SPEC \=\SIdIndex{B} \= \Ax{=}\\
\>\SORTS \=\Id{A}, \Id{B}, \Id{F}, \Id{G} \Ax{<} \Id{T}\\
\>\PREDS \=\Id{R1} : \Id{A} \Ax{\times}  \Id{B};\\
\>\> \Id{R2} : \Id{B} \Ax{\times}  \Id{G};\\
\>\> \Id{R3} : \Id{F} \Ax{\times}  \Id{T}\\
\END\\
\\
\SPEC \=\SIdIndex{Combination} \= \Ax{=}\\
\>\SId{A} \WITH \KWC[ID]{sorts} \KWC[ID]{indexed\_by} \Id{A}\\ 
\AND\\
\>\SId{B} \WITH \KWC[ID]{indexed\_by} \Id{B}\\
\END\\

\end{hetcasl}
