TYPECHECKING K-PEBBLE TREE TRANSDUCERS: PRACTICAL EFFICIENCY k-Pebble Tree Transducerに対する静的型検査の実効率 by

Recently, much attention has been drawn on exact typechecking for non-Turing-complete XML transformation languages, such as XSLT and XML-QL. Milo, Suciu, and Vianu proposed a notion of k-pebble tree transducers, a powerful and general framework that can express most of transformations in such languages, and showed that its exact typechecking is decidable in time hyper-exponential to the number k of pebbles. Although the problem is intractable in theoretical point of view, it remains unclear that its practical efficiency is so. In this work, we investigate, through experiments, the practical efficiency of their method with respect to XSLT through experiments. Our typechecker consists of: (1) a converter from XSLT programs to k-pebble tree transducers, and (2) a typechecker for k-pebble tree transducers. As their method relies on decidability of WSkS (weak second-order monadic logic with k successors), we use MONA, an efficient implementation of WSkS solver, in (2). We show and discuss the results from our experiments using, as inputs, several XSLT programs that are actually used.