A survey on tree matching and XML retrieval

International audienceWith the increasing number of available XML documents, numerous approaches for retrieval have been proposed in the literature. They usually use the tree representation of documents and queries to process them, whether in an implicit or explicit way. Although retrieving XML documents can be considered as a tree matching problem between the query tree and the document trees, only a few approaches take advantage of the algorithms and methods proposed by the graph theory. In this paper, we aim at studying the theoretical approaches proposed in the literature for tree matching and at seeing how these approaches have been adapted to XML querying and retrieval, from both an exact and an approximate matching perspective. This study will allow us to highlight theoretical aspects of graph theory that have not been yet explored in XML retrieval

Coloration, placement et plongement de graphes

In this thesis, we investigate some problems in graph theory, namelythe graph coloring problem, the graph packing problem and tree pattern matchingfor XML query processing. The common point between these problems is that theyuse labeled graphs.In the first part, we study a new coloring parameter of graphs called the gapvertex-distinguishing edge coloring. It consists in an edge-coloring of a graph G whichinduces a vertex distinguishing labeling of G such that the label of each vertex isgiven by the difference between the highest and the lowest colors of its adjacentedges. The minimum number of colors required for a gap vertex-distinguishing edgecoloring of G is called the gap chromatic number of G and is denoted by gap(G).We will compute this parameter for a large set of graphs G of order n and we evenprove that gap(G) 2 fn E 1; n; n + 1g.In the second part, we focus on graph packing problems, which is an area ofgraph theory that has grown significantly over the past several years. However, themajority of existing works focuses on unlabeled graphs. In this thesis, we introducefor the first time the packing problem for a vertex labeled graph. Roughly speaking,it consists of graph packing which preserves the labels of the vertices. We studythe corresponding optimization parameter on several classes of graphs, as well asfinding general bounds and characterizations.The last part deal with the query processing of a core subset of XML query languages:XML twig queries. An XML twig query, represented as a small query tree,is essentially a complex selection on the structure of an XML document. Matching atwig query means finding all the occurrences of the query tree embedded in the XMLdata tree. Many holistic twig join algorithms have been proposed to match XMLtwig pattern. Most of these algorithms find twig pattern matching in two steps. Inthe first one, a query tree is decomposed into smaller pieces, and solutions againstthese pieces are found. In the second step, all of these partial solutions are joinedtogether to generate the final solutions. In this part, we propose a novel holistictwig join algorithm, called TwigStack++, which features two main improvementsin the decomposition and matching phase. The proposed solutions are shown to beefficient and scalable, and should be helpful for the future research on efficient queryprocessing in a large XML database.Cette thèse se situe dans le domaine de graphes et de leurs applications, Elleest constitué de trois grandes parties, la première est consacrée à l’étude d’unnouveau type de coloration sommets distinguantes, les arête-colorations sommetsdistinguantespar écarte. Il consiste de trouver une valuation des arêtes qui permettede distinguer les sommets de graphes telle que chaque sommet v du graphe est identifiéde façon unique par la différence entre la plus grande et la plus petite des valeursincidentes à v. Le plus entier pour lequel le graphe G admet une arête-colorationsommets-distinguantes par écarte est le nombre chromatique par écart de G, notégap(G). Nous avons étudié ce paramètre pour diverses familles de graphes. Uneconjecture intéressante, proposée dans cette partie, suggère que le nombre chromatiquepar écart de tout graphe connexe d’ordre n > 2 vaut n - 1, n ou n + 1.La deuxième partie du manuscrit concerne le problème du placement de graphes.Nous proposons un état de l’art des problèmes de placement de graphes, puis nousintroduisons la nouvelle notion de placement de graphes étiquetés. Il s’agit d’unplacement de graphes qui préserve les étiquettes des sommets. Ensuite, nous proposonsdes encadrements de ce nouveau paramètre pour plusieurs classes de graphes.La troisième partie de la thèse s’intéresse au problème d’appariement d’arbres dansle cadre de la recherche d’information dans des documents structurés de type XML.Les algorithmes holistique de jointure structurelle est l’une des premières méthodesproposées pour résoudre l’appariement exact des documents XML. Ces algorithmessont souvent divisés en deux grandes étapes. La première étape permet de décomposerl’arbre de la requête en un ensemble de petites composantes connexes. Ensuite,des solutions intermédiaires pour chaque composante de la requête sont trouvées, cesrésultats intermédiaires sont joints pour obtenir la solution finale. Nous proposonsdans cette partie un nouvel algorithme appelé TwigStack++ qui vise principalementà diminuer le coût de la jointure et le calcule inutile recherche. Notre algorithmeobtient de meilleurs résultats en comparaison avec deux autres méthodes de l’étatde l’art

TwigStack++ : A New Efficient Holistic Twig Join Algorithm

International audienceFinding all occurrences of a twig pattern in an XML document is a core operation for XML query processing. Many holistic twig join algorithms have been proposed to match XML twig pattern. Most of these algorithms find twig pattern matching in two phases. In the first phase, a query tree is decomposed into smaller pieces, and solutions against these pieces are found. In the second phase, all of these partial solutions are joined together to generate the final solutions. In this paper, we propose a novel holistic twig join algorithm, called TwigStack++, which features two main improvements in the decomposition and matching phase. Experimental results on various datasets show that our algorithm outperforms the existing approaches

Component-cardinality-constrained critical node problem in graphs

International audienceAn effective way to analyze and apprehend the structural properties of networks is to find their most critical nodes. This makes them easier to control, whether the purpose is to keep or to delete them. Given a graph, Critical Node Detection problem (CNDP) consists in finding a set of nodes, deletion of which satisfies some given connectivity metrics in the induced graph. In this paper, we propose and study a new variant of this problem, called Component-Cardinality-Constrained Critical Node Problem (3C-CNP ). In this variant, we seek to find a minimal set of nodes, removal of which constrains the size of each connected component in the induced graph to a given bound. We prove the NP-hardness of this problem on a graph of maximum degree Δ=4Δ=4, through which we deduce the NP-hardness of CNP (Arulselvan et al., 2009) on the same class of graphs. Also, we study 3C-CNP on trees for different cases depending on node weights and connection costs. For the case where node weights and connection costs have non-negative values, we prove its NP-completeness. While, for the case where node weights (or connection costs) have unit values, we present a polynomial algorithm. Also, we study 3C-CNP on chordal graphs, where we show that it is NP-complete on split graphs, and polynomially solvable on proper interval graphs

TwigStack++ : A New Efficient Holistic Twig Join Algorithm

International audienceFinding all occurrences of a twig pattern in an XML document is a core operation for XML query processing. Many holistic twig join algorithms have been proposed to match XML twig pattern. Most of these algorithms find twig pattern matching in two phases. In the first phase, a query tree is decomposed into smaller pieces, and solutions against these pieces are found. In the second phase, all of these partial solutions are joined together to generate the final solutions. In this paper, we propose a novel holistic twig join algorithm, called TwigStack++, which features two main improvements in the decomposition and matching phase. Experimental results on various datasets show that our algorithm outperforms the existing approaches

Gap vertex-distinguishing edge colorings of graphs.

International audienceIn this paper, we study a new coloring parameter of graphs called the gap vertex-distinguishing edge coloring. It consists in an edge-coloring of a graph which induces a vertex distinguishing labeling of such that the label of each vertex is given by the difference between the highest and the lowest colors of its adjacent edges. The minimum number of colors required for a gap vertex-distinguishing edge coloring of is called the gap chromatic number of and is denoted by .We here study the gap chromatic number for a large set of graphs of order and prove that

Gap vertex-distinguishing edge colorings of graphs.

International audienceIn this paper, we study a new coloring parameter of graphs called the gap vertex-distinguishing edge coloring. It consists in an edge-coloring of a graph which induces a vertex distinguishing labeling of such that the label of each vertex is given by the difference between the highest and the lowest colors of its adjacent edges. The minimum number of colors required for a gap vertex-distinguishing edge coloring of is called the gap chromatic number of and is denoted by .We here study the gap chromatic number for a large set of graphs of order and prove that

Labeled embedding of (n, n − 2)-graphs in their complements

International audienceGraph packing generally deals with unlabeled graphs. In a previous paper, the authors have introduced a new variant of the graph packing problem, called the labeled packing of a graph. This problem has recently been studied on trees and cycles. In this note, we present a lower bound on the labeled packing number of any $(n,n-2)$-graph into K_n. This result improves the bound given by Wo\'zniak in 1994

Labeled packing of graphs

International audienc

Water Cleaning by a Continuous Fixed-Bed Column for Cr(VI) Eco-Adsorption with Green Adsorbent-Based Biomass: An Experimental Modeling Study

In this study, chromate adsorption onto red peanut skin (RPS) was investigated in a fixed-bed column; FTIR, PZC, SEM, DLS, and BET were used to evaluate its adsorption properties. The experiments were conducted to determine the effect of physical parameters, including the inlet initial Cr(VI) concentration (100–500 mg L−1), bed height (10–20 cm), and feed flow rate (13.59–23.45 mL min−1). They were carried out to predict breakthrough curves. The adsorption capacity coefficients were determined using the most widely used Bohart–Adams model. It was tested to fit experimental data, for a better understand the dynamic behavior, and for further optimize column performance. It was found that the Cr(VI) uptake decreases when increasing the flow rate and that high chromate concentration and bed height consequently increase the column’s life span. A high column adsorption capacity can be achieved with a higher Cr(VI) concentration due to the higher driving force. The results indicated that the Bohart–Adams model provides a good description (R2 > 0.98) of the experimental data of the Cr(VI)’s removal from the aqueous solution on the RPS suggesting that the surface diffusion is the rate-limiting step in the continues adsorption process.. Breakthrough adsorption capacity is crucial for comparing RPS with other similar materials. Indeed, possible mechanisms have been suggested for illustrating adsorption onto RPS. The obtained results showed significant potential of 26.23 mg g−1 of RPS on Cr(VI) elimination at a natural pH of 5.35. Furthermore, this global investigation allowed for the design of a promising low-cost material for the future scale-up of cleaning wastewater polluted by metal and determine the properly conditions for operating column adsorption. This material provides an economical, efficient means of eliminating pollutants, thus meeting the main aims of the UN Sustainable Development Goals (UN SDGs)