Generating low-cost plans from proofs

Managing inconsistency in databases has long been recognized as an important problem. One of the most promising approaches to coping with inconsistency in databases is the framework of database repairs, which has been the topic of an extensive investigation over the past several years. Intuitively, a repair of an inconsistent database is a consistent database that differs from the given inconsistent database in a minimal way. So far, most of the work in this area has addressed the problem of obtaining the consistent answers to a query posed on an inconsistent database. Repair checking is the following decision problem: given two databases r and r′, is r′ a repair of r? Although repair checking is a fundamental algorithmic problem about inconsistent databases, it has not received as much attention as consistent query answering. In this paper, we give a polynomial-time algorithm for subset-repair checking under integrity constraints that are the union of a weakly acyclic set of local-as-view (LAV) tuple-generating dependencies and a set of equality-generating dependencies. This result significantly generalizes earlier work for subset-repair checking when the integrity constraints are the union of an acyclic set of inclusion dependencies and a set of functional dependencies. We also give a polynomial-time algorithm for symmetric-difference repair checking, when the integrity constraints form a weakly acyclic set of LAV tgds. After this, we establish a number of complexity-theoretic results that delineate the boundary between tractability and intractability for the repair-checking problem. Specifically, we show that the aforementioned tractability results are optimal; in particular, subset-repair checking for arbitrary weakly acyclic sets of tuple-generating dependencies is a coNP-complete problem. We also study cardinality-based repairs and show that cardinality-repair checking is coNP-complete for various classes of integrity constraints encountered in database design and data exchange. Copyright 2009 ACM.

A proof of the (propositional) Craig interpolation theorem for cut-free sequent calculus yields that a sequent with a cut-free proof (or with a proof with cut-formulas of restricted form; in particular, with only analytic cuts) withkinferences has an interpolant whose circuit-size is at mostk. We give a new proof of the interpolation theorem based on a communication complexity approach which allows a similar estimate for a larger class of proofs. We derive from it several corollaries:(1)Feasible interpolation theorems for the following proof systems:(a)resolution(b)a subsystem ofLKcorresponding to the bounded arithmetic theory(α)(c)linear equational calculus(d)cutting planes.(2)New proofs of the exponential lower bounds (for new formulas)(a)for resolution ([15])(b)for the cutting planes proof system with coefficients written in unary ([4]).(3)An alternative proof of the independence result of [43] concerning the provability of circuit-size lower bounds in the bounded arithmetic theory(α).In the other direction we show that a depth 2 subsystem ofLKdoes not admit feasible monotone interpolation theorem (the so called Lyndon theorem), and that a feasible monotone interpolation theorem for the depth 1 subsystem ofLKwould yield new exponential lower bounds for resolution proofs of the weak pigeonhole principle.

The main goal of this chapter is to arrive at a coherent technology for deriving efficient SQL triggers from declarative specifications of arbitrary integrity constraints. The user may specify integrity constraints declaratively as closed queries in predicate calculus syntax (i.e., sentences in the language of first-order logic, abbr. FOL), as datalog denials, as query conditions in SQL WHERE clauses, or in some other, possibly more user-friendly manner (e.g., via a dialog-driven graphical or natural language interface which internally translates to equivalent WHERE clause conditions). As we are going to see, the triggers derived from such specifications behave such that whenever some update event would violate any of the integrity constraints, one or several of the triggers derived from that constraint are activated in order to enforce the constraint. That is, the violation is either prevented by rolling back the update or repaired instantly by subsequent further updates.

Query join ordering optimization with evolutionary multi-agent systems

A sound and complete model-generation procedure for consistent and confidentiality-preserving databases

In this paper we discuss stochastic optimal path problems where the goal is to find a path that has minimal expected cost and at the same time is less risky (in terms of travel time) than a given benchmark path. The model is suitable for a risk-averse traveler who prefers a path with a more guaranteed travel time to another path that could be faster but could also be slower. Such risk attitude is incorporated using the concept of second order stochastic dominance constraints. A recently developed theory for optimization problems with stochastic dominance constraints ensures that the resulting problem can be written as a large linear integer program with binary variables; for networks of realistic size, however, such a direct approach is not practical because of the size of the resulting optimization problem. Moreover, the solution returned by the model may contain cycles, which is clearly undesirable from a practical perspective. A number of strategies are explored to solve the problem. First, we prove that cycles can be prevented by a simple modification of the model if the arc travel times are mutually independent. We then propose a sample average approximation approach to the problem using samples from the distribution of travel times. Because of the randomness resulting from sampling, it is important that statistical guarantees for the solution returned by the algorithm be given, and we provide heuristic procedures to deal with stochastic constraints. We also incorporate a branch-and-cut approach that exploits the structure of the problem to deal with the integrality constraints more efficiently. We present some numerical experiments for a 1,522-arc system that corresponds to a large portion of the Chicago area network. The results show that our approach can solve the problem very effectively, producing solutions with statistical guarantees of optimality within a reasonable computational time.

We describe an approach to learning predictive models from large databases in settings where direct access to data is not available because of massive size of data, access restrictions, or bandwidth requirements. We outline some techniques for minimizing the number of statistical queries needed; and for efficiently coping with missing values in the data. We provide open source implementation of the decision tree and naive Bayes algorithms to demonstrate the feasibility of the proposed approach.

Expressions for this polynomial have been given first by C. Hermite [1] and then by P. Johansen, according to W. Simonsen [2] who gives an alternative proof of Johansen's expression for the formula. What appears to be the simplest and most direct expression for Hermite's general osculatory interpolation polynomial has been given first by T. N. E. Greville [3] and then by J. Kuntzmann [4], their formulas being identical in form. In the important special case where the same number of derivatives is prescribed at each point xi, or ri 1 = r 1, but where the points xi still preserve their generally irregular spacing, it is possible to present an approach to Hermite's formula that appears to the writer to be simpler and more frontal, as well as with somewhat more motivation. Of course, the same result can be seen to follow at once from Greville's or Kuntzmann's more general expressions. But the point is that this direct approach is apparently not applicable to the fully general case when we have a different number of derivatives at each point xi, and where the motivation for the result is somewhat less apparent. We shall give this alternative proof here, and then see how it suggests the solution of a problem which is to obtain the corresponding finite difference analogue of Hermite's general (except that every ri = r) formula. In this alternative approach we begin by employing a certain general form for P(x), which is suggested by the explicit formula for the coefficients for r = 2 [5, 6, 7] and for r = 3 [8]. Let us assume that there is a formula like n r-1

Integrability for the generalised variable-coefficient fifth-order Korteweg–de Vries equation with Bell polynomials

Does the surgical approach affect quality of life outcomes? – A comparison of minimally invasive parathyroidectomy with open parathyroidectomy

Objectives: To describe a direct access partial nephrectomy technique through a transperitoneal working space (Roskilde technique).Materials and methods: Prospective single-center descriptive study between April 2015 and January 2017. The surgical outcomes are evaluated according to the Trifecta criteria (negative margins, warm ischemia time < 20 min and a Clavien-Dindo complication score < 3).Surgical procedure: The same access to the transperitoneal cavity as in a Standard transperitoneal Partial Nephrectomy was used. A direct access was established by incision of the peritoneum directly onto the renal fascia. The renal vessels and tumor were identified and the tumor removed with standard technique. The perinephric fat and peritoneum were then closed with a running suture.Results: In total, 122 patients underwent the Roskilde technique. The mean age was 62.2 years, the median Padua score was 12 (IQR = 9–12) and the median tumor size was 32 mm (IQR = 12–90). The median operative time was 101 min (IQR = 90–125). The trifecta achievement criteria goal was achieved in 116/122 (95%), with a median warm ischemia time of 8 min (IQR = 0-12).Conclusions: The Roskilde technique is safe and feasible. It can be performed on complex renal masses, and it seems to result in short operative times and high Trifecta achievement.Trial registration: None

3:09 PM Abstract No. 333 Treatment approach for percutaneous ablation of metastatic adrenal masses

Tissue-sparing surgery for hip replacement aims to minimize muscle damage and conserve the femoral neck through the use of mini-prostheses. We propose a modification of the classical direct lateral access procedure that preserves the gluteus medius. Further advantages during the surgical phase include limited blood loss, visualization of the entire acetabulum, and sparing of the transverse ligament. Precise implantation is facilitated and normal biomechanics are preserved. The gluteus medius is divided longitudinally between the anterior third and posterior two-thirds to provide access to the gluteus minimus, which is detached from the femoral insertion together with a small portion of the vastus lateralis, forming a flap that exposes the underlying articular capsule. When the femoral head is revealed, a decision is made to either continue with its dislocation directly or to resect it and remove it separately to avoid damaging the gluteus medius during dislocation. Upon removal of the femoral head, with the limb flexed and slightly over-rotated, the acetabulum is completely visible. Limb length is maintained through the use of reference stitches on the gluteus minimus tendon and the proximal insertion of the vastus lateralis. In keeping with the minimally invasive philosophy, only pathological tissue is removed (marginal osteophytes, geodes, joint capsule, cartilage to the point of bleeding and pulvinar). We have performed more than 2,000 implants with this procedure since 1990. Advantages and potential critical points are discussed.

Transcatheter aortic valve implantation via surgical subclavian versus direct aortic access: A United Kingdom analysis

Risk indication of genetically modified organisms (GMO): Modelling environmental exposure and dispersal across different scales: Oilseed rape in Northern Germany as an integrated case study