@INPROCEEDINGS{BasinMatthews96,
Author = "David Basin and Sean Matthews",
Title = {Structuring Metatheory on Inductive Definitions},
BOOKTITLE = {The Thirteenth International Conference on Automated
Deduction (CADE-13)},
Year = "1996",
publisher = "Springer-Verlag",
Series = {LNCS},
Volume = "1104"
Pages = "171--185",
ABSTRACT = {
  We examine a problem in formal metatheory: if theories are structured
  hierarchically, there are metatheorems which hold in only some extensions.
  We illustrate this using modal logics and the deduction theorem.  We show
  how statements of metatheorems in such hierarchies can take account of
  possible theory extensions; i.e.~a metatheorem formalizes
  not only the theory in which it holds, but also under what
  extensions, both to the language and proof system, it remains valid.
  We show that FS0, a system for formal metamathematics, provides a
  basis for organizing theories this way, and we report on our
  practical experience.  },
}