We present a solution to the problem of defining a counterpart
in Algebraic Set Theory of the construction of internal
sheaves in Topos Theory. Our approach is general
in that we consider sheaves as determined by
Lawvere—Tierney coverages, rather than by Grothendieck
coverages, and assume only a weakening of the axioms for
small maps originally introduced by Joyal and Moerdijk,
thus subsuming the existing topos-theoretic results.
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