type theory, theory_ref, exception THEORY and related operations imported from Context; actual theory content declared as theory data; removed syn_of; import theory operations in SIGN_THEORY from Sign; tuned;

obsolete type sg is now an alias for Context.theory; code and interfaces related to stamps and data now in context.ML; actual signature content declared as theory data; removed type sg_ref (superceded by theory_ref); signature SIGN_THEORY lists theory operations that are duplicated in Theory;

added theorem_space; removed unused extern_thm_sg; accomodate change of TheoryDataFun; accomodate identification of type Sign.sg and theory; removed theory management (cf. 'history' in context.ML); moved add_typedecls to sign.ML; Sign.init, Theory.init; tuned;

Context.theory_name; tuned;