OF NOMINATIVES AND DATIVES 483guages show a typological range into at least two major classes, that corre
spond in a fundamental way to the distinction between "local" and "global"
case-marking systems in the domain of the single clause. The "local"-type,
called anaphoric reference-maintenance for a shorthand prototype, consists
of some special NP type (among a whole range of possibilities) that occurs
to mark the presupposition of (or, equivalently, to code the entailed)
recoverability of an identifiable entity at that point in discourse. The system
is local in the sense that the formal marking (including its case-marking)
applies in some overt signal relevant to its case-relation in the clause in
which it occurs. Generally, there are heavy restrictions on the range of link
age types and the range of case-relations that an anaphoric element of any
particular form (and there are frequently several forms possible for almost
any structure) appears in. (This is the general principle lying behind the
Keenan-Comrie "accessibility hierarchy" for "local"-type relativization, for
example. See Keenan & Comrie 1977.) Almost always, in addition, the link
age type fixes the case-relation of available antecedents (prior and/or syn
tactically higher NPs) for an anaphoric element, by semantically-coherent
predicate type (in our schema, by propositional regimentation of case-rela
tions) or by classes of such dependent on derived linkage structure (e.g.,
predicate-voice marked forms such as passive or antipassive). Thus, with
antecedent case-relation or its derivative fixed, with linkage type specified,
the only remaining variable for full recoverability of the relevant clause-
level information of an anaphoric element in such a local structure is its
identity and its propositional (intra-clause) case-relation.
The "global'-type of reference maintenance, on the other hand, called
"switch reference" in much of the literature, is a system in which two vari
ables are left free: both the discourse identity of a particular pair of NPs and
the respective case-relations of those NPs in the clauses in which they
occur. In the most familiar sort of system, with fairly straightforward mark
ers, simple affixes on a constituent of the linked clause or the main (inde
pendent or prior) clause indicate not only co-reference of two "kernel" NPs
one in each of the two clauses, but the relative case-relations of the NPs in
the propositional representation of the respective clauses. This usually has
the form of what we call a "same" marker and a "switch" marker, and is
usually restricted to the three canonical case-relations Agent, Patient, and
Subject, and derived structures which are similarly treated. Note that with
three basic propositional case-relations, and two markers, "same" and "dif
ferent," there is a question of which two are going to be paired as counting