Reconciliation between a set of gene trees and a species tree is the most commonly used approach to infer the duplication and loss events in the evolution of gene families, given a species tree. When a species tree is not known, a natural algorithmic problem is to infer a species tree such that the corresponding reconciliation minimizes the number of duplications and/or losses. In this paper, w...

Approximate Quickselect, a simple modification of the well known Quickselect algorithm for selection, can be used to efficiently find an element with rank k in a given range [i..j], out of n given elements. We study basic cost measures of Approximate Quickselect by computing exact and asymptotic results for the expected number of passes, comparisons and data moves during the execution of this a...

We present a novel self-stabilizing algorithm for minimum spanning tree (MST) construction. The space complexity of our solution is O(log n) bits and it converges in O(n) rounds. Thus, this algorithm improves the convergence time of all previously known selfstabilizing asynchronous MST algorithms by a multiplicative factor Θ(n), to the price of increasing the best known space complexity by a fa...

In two previous papers we have investigates the problem of computing the least common subsumer (lcs) and the most specific concept (msc) for the description logic EL in the presence of terminological cycles that are interpreted with descriptive semantics, which is the usual first-order semantics for description logics. In this setting, neither the lcs nor the msc needs to exist. We were able to...

Keyword search enables web users to easily access XML data without understanding the complex data schemas. However, the ambiguity of keyword search makes it arduous to select qualified data nodes matching keywords. To address this challenge in XML datasets whose documents have a relatively low average size, we present a new keyword query semantic model: MAXimal Lowest Common Ancestor (MAXLCA). ...

Methods for computing the least common subsumer (lcs) are usually restricted to rather inexpressive Description Logics (DLs) whereas existing knowledge bases are written in very expressive DLs. In order to allow the user to re-use concepts defined in such terminologies and still support the definition of new concepts by computing the lcs, we extend the notion of the lcs of concept descriptions ...

Most existing XML stream processing systems adopt full structured query languages, such as XPath or XQuery, but they are difficult for ordinary users to learn and use. Keyword search is a user-friendly information discovery technique that has been extensively studied for text documents. This paper presents an XML stream filter system called XKFilter, which is the first system for supporting key...

Several indices that measure the degree of balance of a rooted phylogenetic tree have been proposed so far in the literature. In this work we define and study a new index of this kind, which we call the total cophenetic index: the sum, over all pairs of different leaves, of the depth of their lowest common ancestor. This index makes sense for arbitrary trees, can be computed in linear time and ...