We revisit the foundations of positive model theory, introducing h-inductive sentences. These allow a considerably simplified presentation of positive model theory, as well as a characterisation of Hausdorff cats by an amalgamation property of their $h$-inductive theory.
"Fondements de la logique positive." J. Symbolic Logic 72 (4) 1141 - 1162, December 2007. https://doi.org/10.2178/jsl/1203350777