Footnotes

 

(1)

Department of Information Technology, Technical University of Denmark, DK-2800 Lyngby, Denmark  

(2)

BISS, TZI, FB3, Universität Bremen, P.O. Box 330440, D-28334 Bremen, Germany  

(3)

Subsorted partial first-order logic can in turn be reduced to total first-oder logic, see study note T-2.  

(4)

Should there be a sort isomorphism between ?t and [() -> ? t], and even between [t -> ? u] and [t -> ?u]?  

(5)

If the undefined element were introduced by a constant  |  , it would have to be preserved, but not reflected, and initial models would be maximally defined.