Two of the prime open-source environments available for machine/statistical learning in data mining and knowledge discovery are the software packages Weka and R which have emerged from the machine learning and statistics communities, respectively. To make the different sets of tools from both environments available in a single unified system, an R package RWeka is suggested which interfaces Weka's functionality to R. With only a thin layer of (mostly R) code, a set of general interface generators is provided which can set up interface functions with the usual "R look and feel", re-using Weka's standardized interface of learner classes (including classifiers, clusterers, associators, filters, loaders, savers, and stemmers) with associated methods. / Series: Research Report Series / Department of Statistics and Mathematics

Research has shown that there are gaps in knowledge between newly hired and experienced professionals and that some of these gaps are related to concepts, such as the concepts of object orientation. This problem, and the fact that most computer science majors want to work in the software industry, leads to questions regarding why these gaps exist and how students can be better prepared for their future careers. Against this background, this thesis addresses two theme-based perspectives that focus on students' views of concepts in Computer Science. The first theme-based perspective investigated the existence of potential Threshold Concepts in Computer Science. Such concepts should be troublesome, transformative, irreversible, and integrative. Qualitative methods have been mainly used and empirical data have been collected through semi-structured interviews, concept maps, and written stories. The results identified two Threshold Concepts, suggested several more, and then described the ways in which these concepts have transformed students. The second theme-based perspective took a phenomenographic approach to find the variation in how students understand concepts related to the software profession. Data were collected via semi-structured interviews. In one study the interviews were held in connection with role-playing where students took on the role of a newly hired programmer. The results show a variety of ways to experience the addressed phenomena in the student collective, ranging from superficial views that often have a practical nature to more sophisticated understandings that reflect a holistic approach, including a professional point of view. Educators can use the results to emphasize concepts that are important from students' perspectives. The phenomenographic outcome spaces can help teachers to reflect upon their own ways of seeing contrasted with student conceptions. I have indicated how variation theory can be applied to open more sophisticated ways of seeing, which in this context stresses the professional aspects to help students prepare for becoming professional software developers.

Modern society is intrinsically dependent on the ability to manage data effectively. While relational databases have been the industry standard for the past quarter century, recent growth in data volumes and complexity requires novel data management solutions. These trends revitalized the interest in deductive databases and highlighted the need for column-oriented data storage. However, programming technologies for enterprise computing were designed for the relational data management model (i.e., row-oriented data storage). Therefore, developers cannot easily incorporate emerging data management solutions into enterprise systems. To address the problem above, this thesis presents Deductive Java (DJ), a system that enables enterprise programmers to use a column oriented deductive database in their Java applications. DJ does so without requiring that the programmer become proficient in deductive databases and their non-standardized, vendor-specific APIs. The design of DJ incorporates three novel features: (1) tailoring orthogonal persistence technology to the needs of a deductive database with column-oriented storage; (2) using Java interfaces as a primary mapping construct, thereby simplifying method call interception; (3) providing facilities to deploy light-weight business rules. DJ was developed in partnership with LogicBlox Inc., an Atlanta based technology startup. / Master of Science