XML Reconstruction View Selection in XML Databases: Complexity Analysis and Approximation Scheme

Query evaluation in an XML database requires reconstructing XML subtrees rooted at nodes found by an XML query. Since XML subtree reconstruction can be expensive, one approach to improve query response time is to use reconstruction views - materialized XML subtrees of an XML document, whose nodes are frequently accessed by XML queries. For this approach to be efficient, the principal requirement is a framework for view selection. In this work, we are the first to formalize and study the problem of XML reconstruction view selection. The input is a tree $T$, in which every node $i$ has a size $c_i$ and profit $p_i$, and the size limitation $C$. The target is to find a subset of subtrees rooted at nodes $i_1,\cdots, i_k$ respectively such that $c_{i_1}+\cdots +c_{i_k}\le C$, and $p_{i_1}+\cdots +p_{i_k}$ is maximal. Furthermore, there is no overlap between any two subtrees selected in the solution. We prove that this problem is NP-hard and present a fully polynomial-time approximation scheme (FPTAS) as a solution

Stages of economic substantiation analysis and modeling for the meat processing companies’ price strategy

The authors have presented the stages of economic substantiation analysis and modeling for making decisions on the price strategy as part of management accounting in the articl

Can recombinant tree shrew (Tupaia belangeri chinensis) chymosin coagulate cow (Bos taurus) milk?

Genetically engineered chymosin from the tree shrew (Tupaia belangeri chinensis) has been obtained and partially characterized for the first time. The target enzyme was produced in Escherichia coli, strain BL21(DE3). It was shown that tree shrew recombinant chymosin coagulates cow milk (Bos taurus). The total and specific milk-clotting activity of the obtained enzyme was 0.7–5.3 IMCU/mL and 8.8–16.6 IMCU/mg. The nonspecific proteolytic activity of tree shrew recombinant chymosin in relation to total bovine casein was 30 and 117% higher than that of recombinant chymosin of cow and of single-humped camel respectively. It was found that in comparison with most of the known genetically engineered chymosins, the tree shrew enzyme showed exceptionally low thermal stability. After heating at 45°C, the coagulation ability of tree shrew recombinant chymosin decreased by more than 40%, and at 50°C the enzyme lost more than 90% of the initial milk-clotting activity. The Michaelis constant (Km), enzyme turnover number (kcat), and catalytic efficiency (kcat/Km) for genetically engineered chymosin from the tree shrew were 6.3 ± 0.1 µM, 11 927 ± 3169 s–1 and 1968 ± 620 µM–1 s–1, respectively. Comparative analysis showed that the primary structure of the chymosin-sensitive site of cow kappa-casein and the supposed similar sequence of tree shrew kappa-casein differed by 75%. The ability of tree shrew recombinant chymosin to coagulate cow’s milk, along with a low thermal stability and high catalytic efficiency with respect to the substrate, imitating the chymosin-sensitive site of cow kappa-casein, suggests that this enzyme is of potential interest for cheese making

МЕТОД ПОВЫШЕНИЯ КАЧЕСТВА СПЕЦИФИКАЦИИ ТРЕБОВАНИЙ К ПРОГРАММНОМУ СРЕДСТВУ

The graph model for software requirements specification is proposed. Besides, there are possible actions of improving the quality characteristics of software requirements described. In total proposed model and actions represent a method of the quality improvement of the software requirement specification.Предложена графовая модель спецификаций требований. При построении графовой модели описаны действия, которые позволяют обеспечить соответствие требований критериям качества, что в совокупности представляет собой метод повышения качества спецификации требований к программному средству

LIFETIME OF SPIRAL DYNAMIC DOMAINS IN IRON GARNET FILMS

In this paper investigation of lifetime of spiral dynamic domains in iron garnet film in magnetic field with a constant gradient field was performed. It is shown that dependence of spiral domains lifetime on amplitude of magnetic field has a peak in the middle of the amplitude range of spiral domains existence.Работа выполнена в рамках базовой части Госзадания Минобрнауки РФ (проект №3.6121.2017)

Social sphere development regularities in regional reproduction in Russia

The article is devoted to the theoretical analysis of social enterprise development in the reproduction process. As a method, the social sphere has analyzed the system of enterprise effective functioning. As a result, one of the key tasks of the regional reproduction process improvement is the effective development of the social sphere. In conclusion, a necessary condition for the rational combination of sectoral and regional aspects of social infrastructure development planning is the division of the country territory into region

Changing the PH value of herbal decoctions for determining the optimum storage conditions

The purpose of the study is to find out which degree of purification water is less affected by various environmental conditions to determine the optimal temperature regimes for storage of decoctions.Цель исследования - выяснить, вода какой степени очистки меньше подвержена влиянию различных условий внешней среды и определить оптимальные температурные режимы хранения отваров

SemLAV: Local-As-View Mediation for SPARQL Queries

International audienceThe Local-As-View(LAV) integration approach aims at querying heterogeneous data in dynamic environments. In LAV, data sources are described as views over a global schema which is used to pose queries. Query processing requires to generate and execute query rewritings, but for SPARQL queries, the LAV query rewritings may not be generated or executed in a reasonable time. In this paper, we present SemLAV, an alternative technique to process SPARQL queries over a LAV integration system without generating rewritings. SemLAV executes the query against a partial instance of the global schema which is built on-the-fly with data from the relevant views. The paper presents an experimental study for SemLAV, and compares its performance with traditional LAV-based query processing techniques. The results suggest that SemLAV scales up to SPARQL queries even over a large number of views, while it significantly outperforms traditional solutions