e type system for the lmdElulus enrihed with reurE sive nd oreursive funtions over equiEindutive nd Eoindutive types is presented in whih ll wellEtyped progrms re strongly normlizingF he hoie of equiEindutive typesD insted of the more ommon isoE indutive typesD in)uenes oth redution rules nd the strong normlE iztion proofF fy emedding isoE into equiEtypesD the ltter ones re reognized s more fundmentlF e model sed on orthogonlity is onE struted where semntil type orresponds to set of oservtionsD nd soundness of the type system is provenF