Functorial semantics and HSP type theorems

نویسندگان

  • Michael Barr
  • Alan Day
چکیده

We show that if C is the category of models for a theory in the sense of Linton over an arbitrary base category, then a full subcategory of C is closed under Homomorphic images that split in the underlying category, under M -Subobjects for a class M of monomorphisms and under Products if and only if it is an intersection of a nest of subcategories, each determined from the preceding by a class of “Horns”, in which the crucial arrow lies in the class E of epimorphisms orthogonal to M .

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تاریخ انتشار 2004