Solving satisfiability, *implication, and equivalence problems in database systems

Satisfiability, implication and equivalence problems are important and widely-encountered database problems that need to be efficiently and effectively solved. We provide a comprehensive and systematic study of these problems. We consider three popular types of arithmetic inequalities, (X op C), (X op Y), and (X op Y + C), where X and Y are attributes, C is a constant of the domain of X, and op $\in\ \{{<},\ {\le},\ {=},\ {\not=},\ {>},\ {\ge}\}.$ These inequalities are most frequently used in a database system, since the first type of inequalities represents $\theta$-join, the second type represents selection, and the third type is popular in deductive databases. We study the problems under the integer domain and the real domain, as well as under two different operator sets.^ Our results show that solutions under different domains and/or different operator sets are quite different. In this dissertation, we either report the first necessary and sufficient conditions as well as their efficient algorithms with complexity analysis, or provide improved algorithms. ^

Customer Satisfaction and Behavioral Intentions: The Case of Aruba-- Small Island Nation

Tourism studies related to small island destinations have become a research stream amongst many academics in recent years. The current study investigates tourist satisfaction related to a tour operator on the island of Aruba that specializes in jeep and bus tours. As there is an increased expenditure pattern for these types of activities, companies are looking for ways to improve customer satisfaction and behavioral intentions. Results indicate that tourists are generally satisfied with the tour company; however a difference in satisfaction ratings was obtained for respondents 61 years old or above. Four factors were extracted from tourists’ satisfaction attributes and three of these factors, including the overall tour value, tour guide, and sound systems used during these tours, were found to be strong predictors of behavioral intentions measured by the likelihood to rebook and the likelihood to recommend the tour company to family and friends. Operational and marketing strategies were suggested based on the findings of the study.

Petrologic and geochemical study of crustal xenoliths from Calbuco Volcano, Chile (latitude 41°20ʹS)

Twenty Four samples of xenoliths and country rocks from the 1961 lava flow of Calbuco volcano have been studied. Fourteen samples have been analyzed for major elements and P, Ni, Ba, Cr, V, Zr, Sc, Y, and Sr. Five of these samples were further analyzed for Sm, Nd, Sr, and Pb isotope ratios. Seventeen samples were studied under the microscope and three samples were analyzed by microprobe for their pyroxene compositions. Based on petrographic studies xenoliths were divided into three groups. Fine grained xenoliths (groups I and II) probably formed from metamorphosed MORB-like basalts, whereas coarse grained xenoliths (group III) were apparently derived from cumulate minerals that crystallized from the Calbuco magma. The fine grained xenoliths were probably entrained in magma at intermediate levels of the crust, near the stability limit of amphibole to form pyroxene and plagioclase. In the coarse grained xenoliths amphibole that formed at depth dehydrated as the xenoliths were brought to the surface. The country rocks are apparently unrelated to the xenoliths.

Can Technologies and Social Media Accelerate Cuba's Democratization?

This flyer promotes a lecture by Cuban blogger and independent journalist Yoani Sanchez, founder of the blog Generacion Y and one of Time Magazine's 100 most influential people in the world. This lecture was held at the Wertheim Performing Arts Center at FIU Modesto A. Maidique Campus on April 1,2013.