Pierre Bourhis

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ManyWeb applications are based on dynamic interactions between Web components exchanging flows of information. Such a situation arises for instance in mashup systems [22] or when monitoring distributed autonomous systems [6]. This is a challenging problem that has generated recently a lot of attention; see Web 2.0 [38]. For capturing interactions between(More)
Query evaluation in monadic second-order logic (MSO) is tractable on trees and treelike instances, even though it is hard for arbitrary instances. This tractability result has been extended to several tasks related to query evaluation, such as counting query results [3] or performing query evaluation on probabilistic trees [10]. These are two examples of(More)
Many Web applications are based on dynamic interactions between Web components exchanging flows of information. Such a situation arises for instance in mashup systems or when monitoring distributed autonomous systems. Our work is in this challenging context that has generated recently a lot of attention; see Web 2.0. We introduce the axlog formal model for(More)
We address the problem of comparing the expressiveness of workflow specification formalisms using a notion of <i>view</i> of a workflow. Views allow to compare widely different workflow systems by mapping them to a common representation capturing the observables relevant to the comparison. Using this framework, we compare the expressiveness of several(More)
The containment problem of Datalog queries is well known<lb>to be undecidable. There are, however, several Datalog frag-<lb>ments for which containment is known to be decidable, most<lb>notably monadic Datalog and several “regular” query lan-<lb>guages on graphs. Monadically Defined Queries (MQs) have<lb>been introduced recently as a joint generalization of(More)
Towards a data-centric workflow approach, we introduce an artifact model to capture data and workflow management activities in distributed settings. The model is built on Active XML, i.e., XML trees including Web service calls. We argue that the model captures the essential features of business artifacts as described informally in [1] or discussed in [2].(More)
Regular path queries (RPQs) define query patterns in terms of regular expressions and are therefore well-suited to query for paths over roles in DL. RPQs can be extended to 2-way RPQs (with converse), CRPQs (with conjunctions), or PRPQs (arbitrary positive Boolean combinations), all of which have been explored in DL research. Another natural extension of(More)
The analysis of datalog programs over relational structures has been studied in depth, most notably the problem of containment. The analysis problems that have been considered were shown to be undecidable with the exception of (i) containment of arbitrary programs in nonrecursive ones, (ii) containment of monadic programs, and (iii) emptiness. In this(More)