1 research outputs found
Structural Complexity of Multi-Valued Partial Functions Computed by Nondeterministic Pushdown Automata
This paper continues a systematic and comprehensive study on the structural
properties of CFL functions, which are in general multi-valued partial
functions computed by one-way one-head nondeterministic pushdown automata
equipped with write-only output tapes (or pushdown transducers), where CFL
refers to a relevance to context-free languages. The CFL functions tend to
behave quite differently from their corresponding context-free languages. We
extensively discuss containments, separations, and refinements among various
classes of functions obtained from the CFL functions by applying Boolean
operations, functional composition, many-one relativization, and Turing
relativization. In particular, Turing relativization helps construct a
hierarchy over the class of CFL functions. We also analyze the computational
complexity of optimization functions, which are to find optimal values of CFL
functions, and discuss their relationships to the associated languages.Comment: (Extended Abstract, A4, 10pt, 8 pages) This extended abstract has
already appeared in the Proceedings of the 15th Italian Conference of
Theoretical Computer Science (ICTCS 2014), September 17-19, Perugia, Italy,
CEUR Workshop Proceedings, vol.1231, pp.225-236, 201