Entwurf und Implementierung eines SQL-normkonformen Datenbankkatalogs für ein relationales Datenbankmanagementsystem     

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   

Implicit and explicit attitudes towards sport among young elite athletes with high versus low burnout symptoms     

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   

The role of viewing distance and viewing angle on referees’ decision-making performance during the FIFA World Cup 2014     

Ernst-Joachim Hossner  Urs Schnyder  Jürg Schmid  Ralf Kredel 《Journal of sports sciences》2019,37(13):1481-1489

The present study aims to reveal the effects of positioning on decision-making performance in top-level refereeing in association football. To this end, for all 64 matches of the FIFA World Cup 2014, potential foul-play situations were videometrically analysed in terms of the referee’s position relative to the infringement. Contrary to earlier studies, viewing angles were analysed in addition to viewing distances and error rates were considered for not only falsely whistled but also falsely non-whistled events. Moreover, direct logistic regression analysis was applied to detect position-dependent differences. For the total of 1,527 potential foul play situations, an overall low error rate of 6.9% was found. The similar numbers of total whistle (n = 52) and non-whistle errors (n = 54) reflect referees’ ability to balance both types of errors. Regarding the overall viewing-distance effect, referees were 2.58 times (95% CI 1.47–4.54) more likely to commit a whistle error at 10–15 m and 5.51 times (95% CI 1.35–22.47) more likely to commit a non-whistle error at 0–5 m, corresponding to the position ranges occurring with the highest (10–15 m: 30.3%) and lowest (0–5 m: 5.8%) frequencies. In contrast, no significant effects of viewing-angle on decision-making accuracy could be revealed.  相似文献   

Quo vadis Sportwissenschaft?     

Prof. Dr. Ralf Brand  Claudia Voelcker-Rehage 《Sportwissenschaft》2014,44(3):131-133

  相似文献   

Fliegender Wechsel     

Ralf Brand  Claudia Voelcker-Rehage 《Sportwissenschaft》2016,46(3):139-142

  相似文献   

Visual perception in alpine ski racing     

Olivia Schläppi  Jan Urfer  Ralf Kredel 《Sportwissenschaft》2016,46(3):201-212

  相似文献   

When virtual reality meets realpolitik: Social media shaping the Arab government–citizen relationship     

Ralf Klischewski 《Government Information Quarterly》2014

Since most activists participating in the recent uprisings in Arab countries have been using social media to an unprecedented extent, public analyst and researchers have rushed to reflect on and explain the phenomena, often attributing a ‘change agency’ to social media as such. This argumentative research collects evidence from literature, recent surveys and focus groups in order to contextualize our understanding of the role of social media and its usage in reshaping the Arab government–citizen relationship: Are the traits of social media significant enough to single them out and discuss their specific impact on the government–citizen relationship? Are we well advised to attribute an ‘agency’ of social media in shaping politics and inducing political change? And in view of the actual use of social media: What are the options of containing emerging ‘destructive’ phenomena and ‘improving’ the government–citizen relationship? Answers are outlined to support contextualized design of social media technology and regulation: (1) Arab citizens basically support democratic concepts; however (2) social media as such do not act and therefore do not ‘create’ e.g. democracy; rather (3) social media enable a new political sphere for Arab citizens, nevertheless challenged by realpolitik; and (4) social media need care taking in terms of shaping political communication and shaping the media itself in order to serve well as mediator among citizens and between citizens and government.  相似文献   

Können (und wollen) wir uns soziale Kompetenz leisten?     

Ralf Meutgens 《Sportwissenschaft》1997,27(1):103-106

  相似文献   

Linking service development methods to interoperability governance: The case of Egypt     

Ralf Klischewski  Eman Askar 《Government Information Quarterly》2012

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   

On File Sharing With Indirect Network Effects Between Concert Ticket Sales and Music Recordings     

Ralf Dewenter  Justus Haucap  Tobias Wenzel 《Journal of Media Economics》2013,26(3):168-178

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