Anne-Cécile Caron

Encompassment Properties and Automata with Constraints

We introduce a class of tree automata with constraints which gives an algebraic and algorithmic framework in order to extend the theorem of decidability of inductive reducibility. We use automata with equality constraints in order to solve encompassment constraints and we combine such automata in order to solve every first order formulas built up with unary predicates “x encompasses t” denoted by encompt(x).

View update translation for XML

We study the problem of update translation for views on XML documents. More precisely, given an XML view definition and a user defined view update program, find a source update program that translates the view update without side effects on the view. Additionally, we require the translation to be defined on all possible source documents; this corresponds to Hegners notion of uniform translation. The existence of such translation would allow to update XML views without the need of materialization. The class of views we consider can remove parts of the document and rename nodes. Our update programs define the simultaneous application of a collection of atomic update operations among insertion/deletion of a subtree and node renaming. Such update programs are compatible with the XQuery Update Facility (XQUF) snapshot semantics. Both views and update programs are represented by recognizable tree languages. We present as a proof of concept a small fragment of XQUF that can be expressed by our update programs, thus allows for update propagation. Two settings for the update problem are studied: without source constraints, where all source updates are allowed, and with source constraints, where there is a restricted set of authorized source updates. Using tree automata techniques, we establish that without constraints, all view updates are uniformly translatable and the translation is tractable. In presence of constraints, not all view updates are uniformly translatable. However, we introduce a reasonable restriction on update programs for which uniform translation with constraints becomes possible.

Deciding the Satisfiability of Quantifier free Formulae on One-Step Rewriting

We consider quantifier free formulae of a first order theory without functions and with predicates x rewrites to y in one step with given rewrite systems. Variables are interpreted in the set of finite trees. The full theory is undecidable [Tre96] and recent results [STT97], [Mar97], [Vor97] have strengthened the undecidability result to formulae with small prefixes (∃*∀*) and very restricted classes of rewriting systems (e.g. linear, shallow and convergent in [STTT98]). Decidability of the positive existential fragment has been shown in [NPR97]. We give a decision procedure for positive and negative existential formulae in the case when the rewrite systems are quasi-shallow, that is all variables in the rewrite rules occur at depth one. Our result extends to formulae with equalities and memberships relations of the form x ∈ L where L is a recognizable set of terms.

Static analysis of XML security views and query rewriting

In this paper, we revisit the view based security framework for XML without imposing any of the previously considered restrictions on the class of queries, the class of DTDs, and the type of annotations used to define the view. First, we study query rewriting with views when the classes used to define queries and views are Regular XPath and MSO. Next, we investigate problems of static analysis of security access specifications (SAS): we introduce the novel class of interval-bounded SAS and we define three different manners to compare views (i.e. queries) from a security point of view. We provide a systematic study of the complexity for deciding these three comparisons, when the depth of the XML documents is bounded, when the document may have an arbitrary depth but the queries defining the views are restricted to guarantee the interval-bounded property, and in the general setting without restriction on queries and document.

Decidability of reachability for disjoint union of term rewriting systems

Abstract The reachability problem for term rewriting systems is the problem of deciding for a system S and two terms t and t ′, whether t can be reduced to t ′ with rules of S . On the one hand, we study the disjoint union of term rewriting systems the reachability problem of which is decidable and give sufficient conditions for obtaining the modularity of decidability of this problem. On the other hand, we study composition of constructor systems. This notion of composition does not imply disjointness.

Negotiation Strategy of Divisible Tasks for Large Dataset Processing

MapReduce is a design pattern for processing large datasets on a cluster. Its performances depend on some data skews and on the runtime environment. In order to tackle these problems, we propose an adaptive multiagent system. The agents interact during the data processing and the dynamic task allocation is the outcome of negotiations. These negotiations aim at improving the workload partition among the nodes within a cluster and so decrease the runtime of the whole process. Moreover, since the negotiations are iterative the system is responsive in case of node performance variations. In this paper, we show how, when a task is divisible, an agent may split it in order to negotiate its subtasks.

ON DECIDABILITY OF BOUNDEDNESS PROPERTY FOR REGULAR PATH QUERIES

The paper studies the evaluation of regular path queries on semi-structured data, i.e. path queries of the form nd all objects reachable by path whose labels form a word in p where p is a regular expression. We use local information expressed in the form of path inclusions in the optimization of path queries. These constraints are of the form L v where L is a regular language and v is a word; L v means that the answer to L from a given site is included in the answer to v. We call these inclusions RW-path inclusions. The boundedness problem for regular path queries p with respect to a nite set of path inclusions E is to decide whether the answer to p is included in the answer to a nite path query. We prove that the boundedness problem is decidable for regular path queries w.r.t. a set of RW-path inclusions, extending a result of Abiteboul and Vianu in 1].