Appendix: Math notation
A few times in this manual, formal "proof trees" are used for natural deduction-style definition of various relations.
The following grammar and assignment of metavariables to syntactic categories is used in these sections.
\begin{align} s, t &\in \text{store-path} \\ o &\in \text{output-name} \\ i, p &\in \text{deriving-path} \\ d &\in \text{derivation} \end{align}
\begin{align} \text{deriving-path} \quad p &::= s \mid (p, o) \end{align}