\starttext

\setupreferencing[prefix=a]

\chapter[one]{First}

\placefigure[here][fig:alpha]{alpha}{}

\in{one}[one] \in{one}[a:one] \in{alpha}[fig:alpha] \par
\in{two}[two] \in{two}[b:two] \in{beta} [fig:beta]

\setupreferencing[prefix=b]

\chapter[two]{Two}

\placefigure[here][fig:beta]{beta}{}

\in{one}[one] \in{one}[a:one] \in{alpha}[fig:alpha] \par
\in{two}[two] \in{two}[b:two] \in{beta} [fig:beta]

\stoptext
