Results 1  10
of
25
Frontiers of tractability for typechecking simple XML transformations
 PODS
, 2004
"... Typechecking consists of statically verifying whether the output of an XML transformation is always conform to an output type for documents satisfying a given input type. We focus on complete algorithms which always produce the correct answer. We consider topdown XML transformations incorporating X ..."
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Cited by 32 (6 self)
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Typechecking consists of statically verifying whether the output of an XML transformation is always conform to an output type for documents satisfying a given input type. We focus on complete algorithms which always produce the correct answer. We consider topdown XML transformations incorporating XPath expressions and abstract document types by grammars and tree automata. By restricting schema languages and transformations, we identify several practical settings for which typechecking is in polynomial time. Moreover, the resulting framework provides a rather complete picture as we show that most scenarios can not be enlarged without rendering the typechecking problem intractable. So, the present research sheds light on when to use fast complete algorithms and when to reside to sound but incomplete ones.
Exact XML type checking in polynomial time
 In ICDT
, 2007
"... f on valid inputs conform to theoutput type? Since XML types are intrinsically more complex than the types found in ..."
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Cited by 32 (3 self)
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f on valid inputs conform to theoutput type? Since XML types are intrinsically more complex than the types found in
Expressive power of pebble automata
 In Proc. Int. Coll. on Automata Languages and Programming
, 2006
"... Abstract. Two variants of pebble treewalking automata on trees are considered that were introduced in the literature. It is shown that for each number of pebbles, the two models have the same expressive power both in the deterministic case and in the nondeterministic case. Furthermore, nondetermini ..."
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Cited by 16 (3 self)
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Abstract. Two variants of pebble treewalking automata on trees are considered that were introduced in the literature. It is shown that for each number of pebbles, the two models have the same expressive power both in the deterministic case and in the nondeterministic case. Furthermore, nondeterministic (resp. deterministic) treewalking automata with n + 1 pebbles can recognize more languages than those with n pebbles. Moreover, there is a regular tree language that is not recognized by any treewalking automaton with pebbles. As a consequence, FO+posTC is strictly included in MSO over trees. 1
Towards practical typechecking for macro tree transducers
, 2007
"... Abstract. Macro tree transducers (mtt) are an important model that both covers many useful XML transformations and allows decidable exact typechecking. This paper reports our first step toward an implementation of mtt typechecker that has a practical efficiency. Our approach is to represent an input ..."
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Cited by 12 (1 self)
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Abstract. Macro tree transducers (mtt) are an important model that both covers many useful XML transformations and allows decidable exact typechecking. This paper reports our first step toward an implementation of mtt typechecker that has a practical efficiency. Our approach is to represent an input type obtained from a backward inference as an alternating tree automaton, in a style similar to Tozawa’s XSLT0 typechecking. In this approach, typechecking reduces to checking emptiness of an alternating tree automaton. We propose several optimizations (Cartesian factorization, state partitioning) on the backward inference process in order to produce much smaller alternating tree automata than the naive algorithm, and we present our efficient algorithm for checking emptiness of alternating tree automata, where we exploit the explicit representation of alternation for local optimizations. Our preliminary experiments confirm that our algorithm has a practical performance that can typecheck simple transformations with respect to the full XHTML in a reasonable time. 1
HigherOrder MultiParameter Tree Transducers . . .
, 2010
"... We introduce higherorder, multiparameter, tree transducers (HMTTs, for short), which are kinds of higherorder tree transducers that take input trees and output a (possibly infinite) tree. We study the problem of checking whether the tree generated by a given HMTT conforms to a given output specif ..."
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Cited by 10 (2 self)
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We introduce higherorder, multiparameter, tree transducers (HMTTs, for short), which are kinds of higherorder tree transducers that take input trees and output a (possibly infinite) tree. We study the problem of checking whether the tree generated by a given HMTT conforms to a given output specification, provided that the input trees conform to input specifications (where both input/output specifications are regular tree languages). HMTTs subsume higherorder recursion schemes and ordinary tree transducers, so that their verification has a number of potential applications to verification of functional programs using recursive data structures, including resource usage verification, string analysis, and exact typechecking of XMLprocessing programs. We propose a sound but incomplete verification algorithm for the HMTT verification problem: the algorithm reduces the verification problem to a modelchecking problem for higherorder recursion schemes extended with finite data domains, and then uses (an extension of) Kobayashi’s algorithm for modelchecking recursion schemes. While the algorithm is incomplete (indeed, as we show in the paper, the verification problem is undecidable in general), it is sound and complete for a subclass of HMTTs called linear HMTTs. We have applied our HMTT verification algorithm to various program verification problems and obtained promising results.
XML transformation by treewalking transducers with invisible pebbles
 In PODS
, 2007
"... The pebble tree automaton and the pebble tree transducer are enhanced by additionally allowing an unbounded number of ‘invisible ’ pebbles (as opposed to the usual ‘visible’ ones). The resulting pebble tree automata recognize the regular tree languages (i.e., can validate all generalized DTD’s) and ..."
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Cited by 10 (1 self)
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The pebble tree automaton and the pebble tree transducer are enhanced by additionally allowing an unbounded number of ‘invisible ’ pebbles (as opposed to the usual ‘visible’ ones). The resulting pebble tree automata recognize the regular tree languages (i.e., can validate all generalized DTD’s) and hence can find all matches of MSO definable nary patterns. Moreover, when viewed as a navigational device, they lead to an XPathlike formalism that has a path expression for every MSO definable binary pattern. The resulting pebble tree transducers can apply arbitrary MSO definable tests to (the observable part of) their configurations, they (still) have a decidable typechecking problem, and they can model the recursion mechanism of XSLT. The time complexity of the typechecking problem for conjunctive queries that use MSO definable binary patterns can often be reduced through the use of invisible pebbles.
Automata with nested pebbles capture firstorder logic with transitive closure
 Logical Methods in Computer Science
"... Vol. 3 (2:3) 2007, pp. 1–27 ..."
S.: The equivalence problem for deterministic MSO tree transducers is decidable
 Inf. Process. Lett
, 2006
"... Abstract. It is decidable for deterministic MSO definable graphtostring or graphtotree transducers whether they are equivalent on a contextfree set of graphs. It is well known that the equivalence problem for nondeterministic (oneway) finite state transducers is undecidable, even when they cann ..."
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Cited by 9 (1 self)
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Abstract. It is decidable for deterministic MSO definable graphtostring or graphtotree transducers whether they are equivalent on a contextfree set of graphs. It is well known that the equivalence problem for nondeterministic (oneway) finite state transducers is undecidable, even when they cannot read or write the empty string [Gri68]. In contrast, equivalence is decidable for deterministic finite state transducers, even for twoway transducers [Gur82]. The question arises whether these results can be generalized from strings to transducers working on more complex structures like, e.g., trees or graphs. There is no accepted notion of finite state transducer working on graphs; instead, it is believed that transductions expressed in monadic secondorder logic (MSO) are the natural counterpart of finite state transductions on graphs. The idea is to define an output graph by interpreting fixed MSO formulas on a given input graph. In fact, if the input and output graphs of such an MSO graph transducer are strings, then the resulting transductions (in the deterministic case) are precisely the deterministic twoway finite state transductions [EH01]. Hence, by the above, equivalence is decidable for deterministic MSO string transducers. A nondeterministic MSO graph
XML Type Checking Using HighLevel Tree Transducer
 In Functional and Logic Programming (FLOPS
, 2006
"... XML type checking recently attracts interests of researchers. We discuss this problem for programs using higher order functions. In particular, we discuss programs modeled by the highlevel tree transducer which was introduced by Engelfriet. We give one algorithm of XML type checking for this tra ..."
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Cited by 6 (1 self)
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XML type checking recently attracts interests of researchers. We discuss this problem for programs using higher order functions. In particular, we discuss programs modeled by the highlevel tree transducer which was introduced by Engelfriet. We give one algorithm of XML type checking for this transducer.
MultiReturn Macro Tree Transducers
 PLANX
, 2008
"... Macro tree transducers are a simple yet expressive formal model for XML transformation languages. The power of this model comes from its accumulating parameters, which allow to carry around several output tree fragments in addition to the input tree. However, while each procedure is enabled by this ..."
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Cited by 6 (1 self)
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Macro tree transducers are a simple yet expressive formal model for XML transformation languages. The power of this model comes from its accumulating parameters, which allow to carry around several output tree fragments in addition to the input tree. However, while each procedure is enabled by this facility to propagate intermediate results in a topdown direction, it still cannot do it in a bottomup direction since it is restricted to return only a single tree and such tree cannot be decomposed once created. In this paper, we introduce multireturn macro tree transducers as a mild extension of macro tree transducers with the capability of each procedure to return more than one tree at the same time, thus attaining symmetry between topdown and bottomup propagation of information. We illustrate the usefulness of this capability for writing practically meaningful transformations. Our main technical contributions consists of two formal comparisons of the expressivenesses of macro tree transducers and its multireturn extension: (1) in the deterministic case, the expressive powers of these two coincide (2) in the nondeterministic case (with the callbyvalue evaluation strategy) multireturn macro tree transducers are strictly more expressive. 1.