suppose $gamma$ is a graph with $v(gamma) = { 1,2, cdots, p}$and $ mathcal{f} = {gamma_1,cdots, gamma_p} $ is a family ofgraphs such that $n_j = |v(gamma_j)|$, $1 leq j leq p$. define$lambda = gamma[gamma_1,cdots, gamma_p]$ to be a graph withvertex set $ v(lambda)=bigcup_{j=1}^pv(gamma_j)$ and edge set$e(lambda)=big(bigcup_{j=1}^pe(gamma_j)big)cupbig(bigcup_{ijine(gamma)}{uv;uin v(gamma_i),vin ...

Database query processing traditionally relies on three alternative join algorithms: index nested loops join exploits an index on its inner input, merge join exploits sorted inputs, and hash join exploits differences in the sizes of the join inputs. Cost-based query optimization chooses the most appropriate algorithm for each query and for each operation. Unfortunately , mistaken algorithm choi...

We investigate whether a sound and complete formal system for join dependencies can be found. We present a system that is sound and complete for tuple generating dependencies and is strong enough to derive join dependencies from join dependencies using only generalized join dependencies in the derivation. We also present a system that sound and complete for tuple generating dependencies and is ...

We introduce the notions of generalized join-hemimorphism and generalized Boolean relation as an extension of the notions of join-hemimorphism and Boolean relation, respectively. We prove a duality between these two notions.Wewill also define a generalization of the notion of Boolean algebra with operators by considering a finite family of Boolean algebras endowed with a generalized join-hemimo...

A new generalization of Fiedler's lemma is obtained by introducing the concept main function a matrix. As applications, universal spectra H-join any graphs (possibly non-regular) and adjacency H-generalized join constrained (arbitrary) vertex subsets are obtained. The generalized corona deduced from graphs. Also, construction infinitely many pairs non-regular cospectral provided.

We consider the problem of evaluating an XQuery query Q (involving only child and descendant axes) on an XML document D. D is stored on a disk and is read from there, in document order. Chen et al. [From Tree Patterns to Generalized Tree Patterns, Intl. Conf. on Very Large Databases, 2003, pp. 237-248] presented an algorithm to convert Q (from a large fragment of XQuery) into a Generalized Tree...