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To find a minimal real change after an update of a database with integrity constraints (IC) expressed by an extended logic program is proven to be a Σ p 2-complete problem. We define a class of operators expanding the input updates correctly with respect to the IC. The particular monotone expansion operator we describe is incrementally computed in square… (More)

Databases with integrity constraints (IC) are considered. For each DB update, i.e. a set of facts to add and of facts to delete, the IC implies its correct expansion: new facts to add and new facts to delete. Simultaneously, e a c h expanded update induces a correct simplii-cation of the IC. In the limit this sequence of expansions and simpliica-tions… (More)

The computational complexity is explored of finding the minimal real change of a database after an update constrained by a logic program. Quite surprisingly, a polynomial time algorithm is discovered which solves this problem for ground IC in partial interpretations. Formulated in a " property " form, even under the premise of fixed database scheme, this… (More)

In this paper we investigate computational complexity of the PERF-consistency and PERF-entailment problems for ground normal logic programs. In [3] it is proved that these problems belong to Σ P 2 and Π P 2 correspondingly. The question of obtaining more accurate results was left as open. We prove that both problems belong to ∆ P 2. Lower bounds on the… (More)

The provability problem for the Horn fragment of linear logic is NP-complete [4, 1]. In this work we investigate various definitions of concurrency proposed in [2] and establish the complexity of the provability problem and the problem of concurrency recognition. The notion of k-maximal concurrency is introduced which guarantees polynomial time provability.… (More)

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