A dual-fibring of a feature-logic and a concatenation-logic is proposed, in which syntactic categorial types ``live in'' feature terms, in contrast to current fibring, in which feature-terms ``live in'' types. The dual-fibring contains also arrow-introduction rules for hypothetical reasoning. It is used to explain some ``privileged features'' in HPSG and their non-unification manipulation.

Mathematical Logic (acm F.4.1), Grammars and Other Rewriting Systems (acm F.4.2), ARTS AND HUMANITIES (acm J.5)
CWI
Information Systems [INS]

Francez, N. (1997). On the direction of fibring feature logics with concatenation logics. Information Systems [INS]. CWI.