Verteilte Metadatenverwaltung und Anfragebearbeitung für Internet-Datenquellen

Wir pr?sentieren in dieser Arbeit das ObjectGlobe-System, ein offenes und verteiltes Anfragebearbeitungssystem auf Internet-Datenquellen. ObjectGlobe erweitert die begrenzten F?higkeiten des Internets bezüglich Anfragebearbeitung, indem es einen offenen Marktplatz schafft, in dem eine Vielzahl von Anbietern Rechenzeit, Daten und Anfrageoperatoren bereitstellen. Den Schwerpunkt dieses Beitrags bildet die im Rahmen des ObjectGlobe-Projekts entwickelte Metadatenverwaltung MDV, ein verteiltes Metadaten-Management-System. Es besitzt eine 3-schichtige Architektur und unterstützt Caching und Replikation in der Mittelschicht, so dass Anfragen lokal ausgewertet werden k?nnen. Benutzer spezifizieren die Informationen, die sie ben?tigen und die repliziert werden, mit Hilfe einer besonderen Regelsprache. Um Replikate aktuell zu halten und die Replikation von neuen und relevanten Informationen anzusto?en, verwendet das MDV-System einen neuartigen Publish & Subscribe-Algorithmus. Wir beschreiben diesen Algorithmus im Detail und zeigen, wie er mit Hilfe eines normalen relationalen Datenbanksystems implementiert werden kann.     

The Impact of Scaffolding and Student Achievement Levels in a Problem-based Learning Environment

This study examined how scaffolds and student achievement levels influence inquiry and performance in a problem-based learning environment. The scaffolds were embedded within a hypermedia program that placed students at the center of a problem in which they were trying to become the youngest person to fly around the world in a balloon. One-hundred and eleven seventh grade students enrolled in a science and technology course worked in collaborative groups for a duration of 3 weeks to complete a project that included designing a balloon and a travel plan. Student groups used one of three problem-based, hypermedia programs: (1) a no scaffolding condition that did not provide access to scaffolds, (2) a scaffolding optional condition that provided access to scaffolds, but gave students the choice of whether or not to use them, and (3) a scaffolding required condition required students to complete all available scaffolds. Results revealed that students in the scaffolding optional and scaffolding required conditions performed significantly better than students in the no scaffolding condition on one of the two components of the group project. Results also showed that student achievement levels were significantly related to individual posttest scores; higher-achieving students scored better on the posttest than lower-achieving students. In addition, analyses of group notebooks confirmed qualitative differences between students in the various conditions. Specifically, those in the scaffolding required condition produced more highly organized project notebooks containing a higher percentage of entries directly relevant to the problem. These findings suggest that scaffolds may enhance inquiry and performance, especially when students are required to access and use them.     

Academic and Social Benefits of a Co-enrollment Model of Inclusive Education for Deaf and Hard-of-Hearing Children

Deaf and hard-of-hearing (d/hh) students are traditionally educated within self-contained programs at residential or special day schools, within self-contained or resource classrooms in public schools, or within regular education classrooms with support provided by an itinerant teacher. The co-enrollment model offers a promising alternative in which these students are educated within a regular education classroom composed of both d/hh and hearing students and team-taught by a teacher of the deaf and a regular education teacher. This article examines the development of one such program and the social and academic performance of the d/hh students within the program. Data on social interaction between d/hh and hearing classmates suggest that specific instructional strategies that promoted students' sign language development, identified d/hh students as "sign language specialists" and grouped d/hh and hearing students during academic activities resulted in increased interaction between these two groups of students. Stanford Achievement Test scores in the areas of reading vocabulary, reading comprehension, mathematical problem solving and procedures indicate that although d/hh students scored below the national normative hearing group, reading comprehension levels exceeded the national normative sample of d/hh students during both years two and three of the program. We discuss the challenges of implementing a co-enrollment program.     

ASSESSING STUDENTS’ EXPERIMENTATION PROCESSES IN <Emphasis Type="Italic">GUIDED INQUIRY</Emphasis>

In recent science education, experimentation features ever more strongly as a method of inquiry in science classes rather than as a means to illustrate phenomena. Ideas and materials to teach inquiry abound. Yet, tools for assessing students’ achievement in their processes of experimentation are lacking. The present study assumes a basal, non-exclusive process model of inquiry in experimentation that can be considered a consensus from multiple approaches: (1) finding an idea/hypothesis, (2) planning and conducting an experiment, and (3) drawing conclusions from evidence. The study confronted 339 secondary level students with three guided inquiry experimentation tasks on 3 days. Selected working groups were videotaped while experimenting. All the students reported their processes in a structured report form simultaneous to their progress. The generated videos and reports were analysed in a two-stepped way: (1) Experimentation was coded according to the process model into process plots; on basis of these, (2) process-focused performance scores were calculated considering logical coherence and immediacy of the inquiry processes. Correlative analyses show for two of the tasks that the report format yielded comparable performance scores to those generated from video data after students have had opportunity to learn the surveying formats (r _S?>?.80). A first suggestion of a process-oriented assessment tool for inquiry in experimentation can be drawn from this study. It might be used to inform and complement secondary science instruction.     

Steps to promote open and authentic dialogue between teachers and school management

Purpose: School principals must determine educational policies and make information-based decisions. Teachers have authentic information that they do not transmit in full to the principals. A theoretical model was tested that explains the factors behind this disconnection in communication.

Design: Four hundred and forty-five teachers completed questionnaires that examined a variety of aspects of reciprocal relations between teachers and school management.

Findings: The model explains 44% of the variance in authentic teacher–principal communication. The principal’s communication pattern with teachers, with two sub-components, represents a dominant factor in teacher willingness to share information. Leadership style represents only an indirect factor.     

American Students’ Perspectives on Alternative Assessment: do they know it's different?

This study used the 1993 California Learning Assessment System (CLAS) Middle Grades Mathematics Performance Assessment as a platform to examine alternative assessment in actual practice in the United States. Reported here is information gathered using the CLAS regarding student attitudes and approaches toward this new type of assessment. At issue is whether students find alternative assessments to be more motivating and interesting than traditional types of tests, and whether they appreciate the difference between traditional and alternative tasks. Data were collected in 13 schools across the state of California, involving more than 800 students. Instrumentation used in data collection included student surveys as well as in‐depth student retrospective interviews. Findings suggest that students do indeed understand the differences in approaches necessitated by novel, open‐ended versus more familiar multiple‐choice tasks. In addition, student attitudes toward these two types of tasks are discussed in detail.