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51.
Steffen Skatulla Ralf Schaarschmidt Peter Pistor und Klaus Küspert 《Informatik - Forschung und Entwicklung》2000,15(3):161-170
Zusammenfassung. Bei relationalen Datenbanksystemen haben sich de-jure-Normen für SQL stetig weiterentwickelt; mit diesen Normen wird es einfacher, portable Datenbankanwendungen zu entwickeln.
Die SQL-Norm ruht auf zwei S?ulen, zum einen auf der Datenbanksprache SQL, zum anderen auf einer Vorgabe eines Datenbankkatalogs,
welcher die gespeicherten Daten beschreiben soll. Im vorliegenden Beitrag wird derjenige Teilbereich des Datenbankkatalogs
der aktuellen SQL99-Norm dargestellt, der bereits in der SQL92-Norm (ISO/IEC 9075:1992 bzw. DIN 66315) definiert ist und die
klassischen (nicht objektrelationalen) Elemente einer relationalen Datenbank beschreibt. In dieser Darstellung nimmt der zweischichtige
Spezifikationsansatz (Informationsschema, Definitionsschema) einigen Raum ein; mit seiner Hilfe weist SQL einen eleganten Weg, auf dem existierende Datenbanksysteme normkonforme Datenbankkataloge
bereitstellen k?nnen. Anhand des Datenbankmanagementsystems DB2 wird anschlie?end untersucht, wie ein normkonformer Datenbankkatalog
(das sogenannte Informationsschema) „oberhalb” des verfügbaren DB2-Katalogs realisiert werden kann, d. h. wie die vom Informationsschema
geforderten Sichten auf DB2-Katalogtabellen abgebildet werden k?nnen. Auf generelle Schwierigkeiten und M?glichkeiten einer
solchen Abbildung (ein- oder zweistufig) wird ebenso eingegangen wie auf Probleme, die sich speziell bei DB2 ergeben. In einer
prototypischen Realisierung konnte das Informationsschema bis auf wenige Einschr?nkungen komplett umgesetzt werden. Damit
wurde die Machbarkeit normkonformer Kataloge nachgewiesen. In heute verfügbaren DBMS-Produkten sind Datenbankkataloge in dieser
konsequent normkonformen Gestalt leider immer noch nicht anzutreffen.
Eingegangen am 5. M?rz 1999 / Angenommen am 1. Mai 2000 相似文献
52.
While administrations, and especially e-government “followers,” have been recommended adopting service-oriented architecture (SOA) for the purpose of implementing G2G interoperability, the challenges of reaching this objective remain significant. General guidelines for service development and SOA governance are published, but in view of many self-contained units and IT departments on all administrative levels as well as widespread outsourcing of software development there is a lack of sharing “best practices” how to implement SOA step by step in the area of e-government. In particular, it is unknown to what extent administrations are able to follow existing service development approaches, and there is no research addressing the contribution of service development methods towards governance, i.e. developing and managing government interoperability. In this research the case of Egypt, where SOA was chosen as the main interoperability approach, has been explored in terms of to what extent the current approach to service development supports the interoperability governance, and what kind of changes in the development methods and their application would yield improvements in interoperability governance. The case analysis on practical and strategic level leads to proposing success factors related to linking the methodology of developing G2G services to the overall effort of interoperability governance. These factors, divided into interoperability problem perception, method scoping and deliverables, measurement of goal achievement, and methodological commitment, can be used as hypotheses in future research and as guidelines for improving the interoperability governance in administrative practice. 相似文献
53.
Markus Gerber Ralf Brand Franziska Antoniewicz Sandrine Isoard-Gautheur Henrik Gustafsson Renzo Bianchi 《Journal of sports sciences》2019,37(14):1673-1680
The development of cynical attitudes towards elite sport is a core symptom of athlete burnout and has been associated with dropout from elite sport. To date, this phenomenon has mainly been studied by investigating explicit attitudes towards sport, whereas athletes’ automatic evaluations (i.e. implicit attitudes) that have been shown to influence behavior as well were not considered. This study aimed to compare explicit and implicit attitudes towards sport of young elite athletes with high (N = 24) versus low (N = 26) burnout symptoms. Using self-reported measures, general and athlete burnout symptoms were assessed. Additionally, a single-target implicit association test was administered to examine participants’ automatic evaluation of sport. Statistical analysis revealed greater emotional/physical exhaustion and sport devaluation in athletes reporting high compared to low burnout symptoms. Implicit attitudes towards sport did not significantly differ between the groups. Furthermore, no significant correlations were observed between different athlete burnout symptoms and implicit attitudes. Athletes with high burnout symptoms show a tendency to explicitly detach themselves from sport, thus fostering sport devaluation as a core symptom of athlete burnout. However, this process does not seem to be reflected in their implicit attitudes towards sport. 相似文献
54.
This article analyzes the interdependency between the market for music recordings on the one side and the market for concert tickets on the other side, assuming that there are positive indirect network effects both from the record market to ticket sales for live performances and vice versa. In a model with two interrelated Hotelling lines, prices in both markets are corrected downward when compared to the standard Hotelling model. In the integrated business model, file sharing has an ambiguous effect on firms' profitability. As file sharing can indirectly increase demand for live performances, overall profits can either increase or decrease, depending on the strength of indirect network effects. Finally, file sharing may induce firms to switch from the traditional business model with two separate firms to an integrated business model where one agency markets both records and concerts (so-called 360° deals). 相似文献
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59.
Christian Saal Jochen Zinner Harald Fiedler Ralf Lanwehr Jürgen Krug 《Sportwissenschaft》2018,48(3):334-340
The aim of this study was to investigate the reliability and validity of a soccer short passing test using the Footbonaut training system. Forty-eight young skilled soccer players and 31 lesser-skilled soccer players completed a test and a retest, each involving four sessions a day of a Footbonaut short passing test (FSPT). We found significant differences in mean execution times for skilled (mean [M]?=?2487, standard deviation [SD] ?=?155) and lesser-skilled players (M?=?2682, SD?=?176) but no significant difference in accuracy (M?=?74.13, SD?=?7.65; M?=?72.19, SD?=?8.13) between groups. The results from linear mixed-effects models show that there were no significant effects of repeated measurements on execution time. In contrast, we found an estimated increase of 0.86% in accuracy per session for both groups. In conclusion, the FSPT offers a reliable and valid method to differentiate young soccer players at different competitive levels, using execution time. 相似文献
60.
This study concentrates in part on the market of fine arts. First, fine arts will be defined from a marketing point of view and peculiarities in the market of fine arts will be analysed empirically and theoretically. Certain aspects of marketing theory are discussed regarding their significance for the fine arts. Results of an empirical study of galleries and artists will be presented. It will be shown, whether and how artists are involved in marketing, how successful they are and what prerequisites to marketing the artists have. 相似文献