We investigate the implication problem for independence atoms X⊥Y of disjoint attribute sets X and Y on database schemata. A relation satisfies X⊥Y if for every X-value and every Y -value that occurs in the relation there is some tuple in the relation in which the X-value occurs together with the Y -value. We establish an axiomatization by a finite set of Horn rules, and derive an algorithm for...

this article is concerned with the question of how much the assured will be entitled to recover following an assured loss. it will be discussed which three elements are involved in this respect; first the loss of assured, second the amount of assuror obligation and third the contractual agreements of the parties in respect of the amount of assuror's payment.it should be noted that franchis...

literal: Let p be a proposition. Then p and -p are literals. clause: A clause is a disjunction of literals. Horn Clause: A Horn Clause is a clause in which there is at most one positive literal. definite clause: A definite clause is a Hom Clause in which there is exactly one positive literal. A definite clause such as can also be written as We call pi the head of the clause, and the conjunction...

Arabic has some special syntax features which lead to complex syntax structures. We have developed a formal description of Arabic syntax in Definite Clause Grammar. This grarnrnar is characterized by its h igh descriptive power due to its dual formulat ion in terms of functions and in terms of grammatical categories. The developed g rammar has a high coverage of Arabic language and has context ...

It is known that bottom-up query evaluation can be extended to work with disjunctive facts, but there seems to be the common assumption that it is much too ineecient for practical applications. In this paper, we improve the extended bottom-up evaluation by making the resolvable literal in a disjunctive fact unique. In many cases, this reduces an exponential behaviour to a polynomial one. We int...

We study inference systems of weak functional dependencies in relational and complex-value databases. Functional dependencies form a very common class of database constraints. Designers and administrators proficiently utilise them in everyday database practice. Functional dependencies correspond to the linear-time decidable fragment of Horn clauses in propositional logic. Weak functional depend...

We establish a new bridge between propositional logic and elementary number theory. A full clause contains all variables, and we study them in minimally unsatisfiable clause-sets (MU); such clauses are strong structural anchors, when combined with other restrictions. Counting the maximal number of full clauses for a given deficiency k, we obtain a close connection to the so-called “Smarandache ...

The interest in dependency grammar has clearly been on the rise in the last 10– 15 years. The parsing community has seen a number of benefits in the use of and parsing with dependency-based representations of syntactic phenomena. On the one hand, dependency trees are much simpler than phrase-structure trees – they contain exactly the same number of nodes as there are tokens in the sentence. The...

The structure of the monoid of autarkies for clause-sets is investigated (autarkies are generalizations of satisfying (truth) assignments). The notion of a \plain clause-set" is introduced, where every clause is usable by some resolution refutation, and it is shown that a clause-set is plain ii it has no non-trivial autarky. Every clause-set has a unique decomposition into a plain sub-clause-se...