Some varieties that are extensions of relational algebras with two constants that play the role of projections are studied. The classes have as a subvariety the abstract fork algebra (AFA) equivalent variety involving projections. They are obtained by weakening some laws valid in AFA. Some applications of the varieties in the literature and in the specification of abstract data types are exhibi...

We present an algorithm for learning correlations among link types and node attributes in relational data that represent complex networks. The link correlations are represented in a Bayes net structure. This provides a succinct graphical way to display relational statistical patterns and support powerful probabilistic inferences. The current state of the art algorithm for learning relational Ba...

Many real-world domains are relational in nature, consisting of a set of objects related to each other in complex ways. This paper focuses on predicting the existence and the type of links between entities in such domains. We apply the relational Markov network framework of Taskar et al. to define a joint probabilistic model over the entire link graph — entity attributes and links. The applicat...

this study focused on the optimization of al—mg to cuzn34 friction stir lap welding (fslw) process for optimal combination of rotational and traverse speeds in order to yield favorable fracture load using grey relational analysis (gra). first, the degree of freedom was calculated for the system. then, the experiments based on the target values and number of considered levels, corresponding orth...

nowadays, in order to reach minimum production cost in machining operations, various optimization methods have been proposed. since turning operation has different parameters affecting the workpiece quality, it was selected as a complicated manufacturing method in this paper. to reach sufficient quality, all influencing parameters such as cutting speed, federate, depth of cut and tool rake angl...

Coalgebraic techniques are applied to the supervisory control of discrete-event systems with partial observations. Classical notions from concurrency theory are specialized to control theory. The concept of weak transitions enables the relational characterization of observability and gives rise to a coalgebraic formulation of the necessary and sufficient conditions for the existence of a superv...

We define filter-tolerant powers of finite relational structures, and consider the problem of retracting such structures to their diagonal. We show that for some structures, such retractions can be readily derived from the axioms of Zermelo and Fraenkel, while at the other extreme, there are structures for which the existence of such retractions is equivalent to the ultrafilter axiom.

In the present paper, as we did previously in [5], we investigate the relations between the geometric properties of tilings and the algebraic and model-theoretic properties of associated relational structures. Our study is motivated by the existence of aperiodic tilings. In [5], we considered tilings of the euclidean spaces R, and isomorphism was defined up to translation. Here, we consider, mo...

Computational methods and tools that can efficiently and effectively analyze the temporal changes in dynamic complex relational networks enable us to gain significant insights regarding the entity relations and their evolution. This paper introduces a new class of dynamic graph patterns, referred to as coevolving relational motifs (CRMs), which are designed to identify recurring sets of entitie...

Thalheim, B., The number of keys in relational and nested relational databases, Discrete Applied Mathematics 40 (1992) 265-282. Combinatorial propositions, concerning the maximal number of minimal keys are considered. It is shown that the results of Demetrovics about the maximal number of minimal keys on unbounded domains do not hold for finite domains. Using this result lower bounds for the si...