\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}