Semantic Similarity Search on Semistructured Data with the XXL Search Engine

Query languages for XML such as XPath or XQuery support Boolean retrieval: a query result is a (possibly restructured) subset of XML elements or entire documents that satisfy the search conditions of the query. This search paradigm works for highly schematic XML data collections such as electronic catalogs. However, for searching information in open environments such as the Web or intranets of large corporations, ranked retrieval is more appropriate: a query result is a ranked list of XML elements in descending order of (estimated) relevance. Web search engines, which are based on the ranked retrieval paradigm, do, however, not consider the additional information and rich annotations provided by the structure of XML documents and their element names.This article presents the XXL search engine that supports relevance ranking on XML data. XXL is particularly geared for path queries with wildcards that can span multiple XML collections and contain both exact-match as well as semantic-similarity search conditions. In addition, ontological information and suitable index structures are used to improve the search efficiency and effectiveness. XXL is fully implemented as a suite of Java classes and servlets. Experiments in the context of the INEX benchmark demonstrate the efficiency of the XXL search engine and underline its effectiveness for ranked retrieval.     

Teachers’ views on risk factors for problematic school absenteeism in Swedish primary school students

In the present online survey, 158 teachers in regular and special education teaching in grades six to nine were asked to rate the importance of probable reasons for problematic school absenteeism. On average, the teachers estimated that among their students, 19 students had presented with problematic school absenteeism over the last five years. Teachers viewed school absenteeism as a multifactorial problem. Family factors were considered to contribute most and low mood or depression were rated as one of the five most contributing factors. Teachers in special education viewed school factors as more influential than teachers in mainstream education did (t₁₅₆ = ?3.94, p < 0.05). The current findings stress the importance of collaboration between the school, parents and the student to be able to address all factors that may lead to problematic school absenteeism.     

Robuste Indizes für Projection Pursuit

Zusammenfassung.   Die moderne und hoch komplexe Fertigung, z.B. in der Halbleiterindustrie, erfordert für die dabei anfallenden Messdaten der Anlagen- bzw. Prozessparameter multivariate Analysemethoden. Eine dieser m?glichen Analysemethoden ist Projection Pursuit (PP). Dieses Verfahren ist durch geschickte Wahl des so genannten Projektionsindex in der Lage, verschiedenste Datencharakteristika zu detektieren und diese auf anschauliche Weise zu visualisieren. Bei den Projektionsindizes handelt es sich um Funktionen, die eine Projektion auf unterschiedliche Merkmale hin bewerten und dabei jeder Projektion einen Funktionswert zuweisen. Dieser Funktionswert spiegelt die Aussagekraft der Projektion (in Abh?ngigkeit vom verwendeten Index) wider. Die Auswahl bzw. der Aufbau dieser Indizes ist hierbei von entscheidender Bedeutung. Alle hier vorgestellten Indizes zeichnen sich vor allem durch ihren robusten Charakter gegenüber durch Ausrei?er kontaminierte Daten, wie sie in realen Datenszenarien vorkommen, aus. Die durch Anwendung dieser Indizes gewonnenen Einblicke in die komplexe Struktur der Daten erm?glichen es, hochdimensionale Parameterabweichungen und komplexe Zusammenh?nge innerhalb der Daten zu finden. Eingegangen am 11. Februar 2002 / Angenommen am 14. Mai 2002     

Teaching at a Distance — Reflections on the relationship between discipline‐based and general teaching theories

German readers would immediately associate the term ‘discipline-based’ with Didaktik, which in the German-speaking world is an established branch of education science. The first section therefore deals with the development of Didaktik, understood as a theory of teaching and learning which seeks to investigate the relationships between discipline-based and general teaching theories. Didaktik was originally a strictly theory-oriented discipline in German-speaking countries, but changes in its terms of reference have led to an acceptance of the more pragmatically oriented curriculum theory of the English-speaking world. The term ‘discipline-based’ seems to indicate that here, too, education science has turned its back on positivistic, ‘purely scientific’ standards, so a knowledge of the German discussion of teaching-learning theory may be of interest.

The second section shows that in distance education, too, general teaching models need concretization in terms of discipline-based teaching theory, and that on the other hand, any discipline-based theory needs to have its foundations in general teaching theory, i.e. in pedagogic principles.

The third section therefore postulates the necessity of a theory of distance education which is based on practical experience.