Relational technology has shown to be very useful for scalable Semantic Web data management. Numerous researchers have proposed to use RDBMSs to store and query voluminous RDF data using SQL and RDF query languages. In this article, we study how RDF queries with the socalled well-designed graph patterns and nested optional patterns can be efficiently evaluated in an RDBMS. We propose to extend ...

To discover knowledge or retrieve information from a relational database, a user often needs to find objects related to certain source objects. There are two main challenges in building an effective object search system: the huge amount of objects in the database and the large number of different relationships between objects. In this paper we introduce Ross, an efficient and accurate relationa...

Motivated by the Eulerian ribbon graph minors, in this paper we introduce notion of checkerboard colourable minors for graphs and its dual: bipartite graphs. abstract graphs, another i.e. join are also introduced. Using these then give excluded minor characterizations classes plane

In this paper, we investigate the problem of efficiently computing a multi-way spatial join without spatial indexes. We propose a novel and effective filtering algorithm based on a two phase partitioning technique. To avoid missing hits due to an inherent difficulty in multi-way spatial joins, we propose to firstly partition a join graph into sub-graphs whenever necessary. In the second phase, ...

A spatial join computes all pairs of spatial objects in two data sets satisfying a distance constraint. An increasing demand in applications ranging from human brain analysis to transportation data analysis motivates studies on designing new in-memory spatial join algorithms. Among recent proposals, the following six algorithms can efficiently perform in-memory spatial joins: Size Separation Sp...

The total chromatic number of a graph G, denoted by χ′′(G), is the minimum number of colors needed to color the vertices and edges of G such that no two adjacent or incident elements get the same color. It is known that if a planar graph G has maximum degree ∆ > 9, then χ′′(G) = ∆ + 1. The join K1 ∨ Pn of K1 and Pn is called a fan graph Fn. In this paper, we prove that if G is an F5-free planar...

For a graph H , f (H ) is the smallest integer k such that the join of H with an empty graph Ek of order k is not |V (H )|-choosable. It was conjectured that for a triangle-free graph G, f (G) = ( 2 )μ(G) nn−2μ(G), where n = |V (G)| and μ(G) is the cardinality of a maximum matching of graph G [S. Gravier, F. Maffray, B. Mohar, On a list-coloring problem, Discrete Math. 268 (2003) 303–308]. We v...

In this paper, we show the values of crossing numbers for join products of graph G on five vertices with the discrete graph Dn and the path Pn on n vertices. The proof is done with the help of software. The software generates all cyclic permutations for a given number n. For cyclic permutations, P1 – Pm will create a graph in which to calculate the distances between all vertices of the graph. T...

RDF query optimization is a challenging problem. Although considerable factors and their impacts on query efficiency have been investigated, this problem still needs further investigation. We identify that decomposing query into a series of light-weight operations is also effective in boosting query processing. Considering the linked nature of RDF data, the correlations among operations should ...

The cyclicity of a hypergraph is an efficiently computable integer that extends the notion of the cyclomatic number of a graph. Generalizing the notion of the degree of a node in a graph, we define the star articulation degree of a subedge in a hypergraph, and then use it to set up the expression for the cyclicity. The basic properties of cyclicity are that it is zero on acyclic hypergraphs and...