An Algebraic Characterization of STUF

Achieving flexibility in unification formalisms

“…PATR-II (Shieber et al, 1983) is the most basic and a kind of common denominator which other formalisms are extensions of. Other formalisms are STUF (Beierle et al, 1988), TFS (Emele & Zajac, 1990), CUF (D6rre & Eisele, 1991) and, ALE (Carpenter, 1992). These formalisms include, for example, disjunction, various variants of negation and typing.…”

“…The subsumption order for closed feature structures shows how fixed arity feature structures (used in, for example, STUF(Beierle et al, 1988)) can be defined. class fs; isa value; constructor empty; constructor closed; constructor add pair:attribute,value,fs; constraint empty>closed; constraint empty>add_pair(A,V, FS); constraint add_pair(A,U,add_pair(A,V, FS))= add_pair(A,and(U,V),FS); constraint add_pair(A,U,add pair(B,V, FS))= add pair(B ,V, add pair(A,U ,FS)).…”

Data types in computational phonology

“…) for the apldication to grammar writing). A second motivation, discussed in detail by (Beierle & Pletat 1988; Beierle K~ Pletat 1989;Beierle et al 1988), is to use equational ADTS to provide a mathematical foundation for h~ature structures. A third motivation, dominant in this pal)er , is to use the AI)T appl'oach lo provide a richer array of explicit data types than are readily admitted by "p'tlre' feature structure approaches.…”