The original 1989 publications on DATR sought to provide the
language with a formal theory of inference (E&G 1989a)
and a model-theoretic semantics (E&G
1989b). Unfortunately, the definitions set out in these
papers are not general enough to cover all of the constructs available
in the DATR language. In particular, they fail to provide a full and
correct treatment of DATR's notion of global inheritance, or the
widely-used evaluable path construct. A denotational semantics for
DATR that covers all of the major constructs is presented in
Section 4. However, it still remains to provide a
suitably general, formal theory of inference for DATR, and it is this
objective that is addressed here. More precisely, an operational
semantics for DATR is provided, comprising a formal system of rules
that axiomatises the essential details of how DATR expressions are
evaluated. Section 3.1.4 has already provided
a concise presentation of the syntax of the DATR language.
Section 5.1 compares the formal theory of inference
presented here to that given in 1989.
Section 5.2 introduces the inference rules for a
restricted version of DATR that is limited to local inheritance.
Section 5.3 extends the rules to allow global
inheritance. Section 5.4 then revises the theory to
bring in path extensions and defaults, thus covering the full DATR language. Finally, in Section 5.5, we make some
comments about the theory of inference presented here.
