Preliminary Experiments using Subjective Logic for the Polyrepresentation of Information Needs

According to the principle of polyrepresentation, retrieval accuracy may improve through the combination of multiple and diverse information object representations about e.g. the context of the user, the information sought, or the retrieval system. Recently, the principle of polyrepresentation was mathematically expressed using subjective logic, where the potential suitability of each representation for improving retrieval performance was formalised through degrees of belief and uncertainty. No experimental evidence or practical application has so far validated this model. We extend the work of Lioma et al. (2010), by providing a practical application and analysis of the model. We show how to map the abstract notions of belief and uncertainty to real-life evidence drawn from a retrieval dataset. We also show how to estimate two different types of polyrepresentation assuming either (a) independence or (b) dependence between the information objects that are combined. We focus on the polyrepresentation of different types of context relating to user information needs (i.e. work task, user background knowledge, ideal answer) and show that the subjective logic model can predict their optimal combination prior and independently to the retrieval process

Methodological aspects of determining nitrogen fixation of different forage legumes

Knowledge about the amount of fixed nitrogen of different legume crops is very important for calculation of farm N balances. According to literature the choice of determination method may have an impact on the estimated amount of N fixed by a legume sward. The aim of the study was to compare the three most important field methods for determination of nitrogen fixation under different sward management systems. In the present study the natural 15N abundance method gave lower fixation rates than the two alternative methods (total-N-difference method and 15N enrichment technique). The determination of N fixation based only on N in harvestable plant material underestimated the amount of fixed N on average by 70 kg ha-1 compared to techniques including also the amount of N in non harvestable plant part

Yield, forage quality, residue nitrogen and nitrogen fixation of different forage legumes

Fixed nitrogen accumulated by legumes is the main nitrogen source for organic farming systems. Knowledge about the amount of fixed nitrogen, its pathways into forage yield, crop residues, soil-N and yield formation of the following crop is needed for designing crop rotations. In a field experiment conducted in Northern Germany differently managed (cut, mulched) legumes (red clover, alfalfa, white clover) in pure stands and in mixture with a companion grass (Lolium perenne) have been grown to determine Yield, forage-quality, N2-fixation and residue nitrogen. Cropped grass/legume reached higher N2-fixation than mulched. While green manure grass/legume left up to 296 kg ha-1 of N in mulch, stubble and roots on the field, most cropped grass/legume mixtures left less than 120 kg N ha-1 in crop residues. Cropped swards showed higher N2-fixation than the mulched mixtures. Swards with red clover or alfalfa reached higher legume contents and harvestable biomass than swards with white clover. Conclusions The results show that biomass production, forage yields, residue nitrogen and N fixation of grass/legume mixtures can be influenced by various combinations of legume species and management. The factors listed have to be considered carefully when planning crop rotations

Una teoría cognitiva integral para la recuperación de información: saliendo del entorno del laboratorio

The paper demonstrates how the Laboratory Research Framework fits into the integrated Cognitive Framework for IR. It first discusses the Laboratory Framework with emphasis on its underlying assumptions and known limitations. This is followed by a view of interaction and relevance phenomena associated with IR evaluation and central to the understanding of IR. The ensuing section outlines how interactive IR is viewed from a Cognitive Framework, and ‘light’ interactive IR experiments are suggested performed by drawing on the latter framework’s contextual possibilities. These include independent variables drawn from a collection, matching principles in a retrieval system, and the searcher’s situation and task context. The paper ends with concluding points of summarization of issues encountered.Este artículo demuestra cómo el marco de investigación en laboratorio encaja bien dentro del marco cognitivo integral para la Recuperación de información. Se discute primero el marco de investigación en laboratorio, con énfasis en sus asunciones y limitaciones. Se analizan los fenómenos de la interacción y relevancia asociados con la evaluación en RI., así como el modo de desarrollar experimentos interactivos de Recuperación de información dentro del marco cognitivo, considerando la situación del investigador y el contexto de la tarea llevada a cabo

Supporting polyrepresentation in a quantum-inspired geometrical retrieval framework

The relevance of a document has many facets, going beyond the usual topical one, which have to be considered to satisfy a user's information need. Multiple representations of documents, like user-given reviews or the actual document content, can give evidence towards certain facets of relevance. In this respect polyrepresentation of documents, where such evidence is combined, is a crucial concept to estimate the relevance of a document. In this paper, we discuss how a geometrical retrieval framework inspired by quantum mechanics can be extended to support polyrepresentation. We show by example how different representations of a document can be modelled in a Hilbert space, similar to physical systems known from quantum mechanics. We further illustrate how these representations are combined by means of the tensor product to support polyrepresentation, and discuss the case that representations of documents are not independent from a user point of view. Besides giving a principled framework for polyrepresentation, the potential of this approach is to capture and formalise the complex interdependent relationships that the different representations can have between each other

Methodische Aspekte zur Bestimmung der symbiontischen N2-Fixierungsleistung von Leguminosen

Die N2-Fixierungsleistung von Leguminosenbeständen ist eine wichtige Kenngröße in der Betriebs-N-Bilanz bzw. der Fruchtfolgeplanung landwirtschaftlicher Betriebe. Aus der Literatur ist bekannt, dass die gewählte Messmethode große Bedeutung für die Höhe der ermittelten N2-Fixierungsleistung von Leguminosen besitzt. Vor diesem Hintergrund wurden 3 alternative Feldmethoden zur Bestimmung der N2-Fixierung vergleichend geprüft. Als Versuchsbestände dienten Futterleguminosenbestände, die sich in den Faktoren Leguminosenart (Rotklee, Weißklee, Luzerne), Saatmischungsverhältnis (Leguminosenreinsaat, Gemenge mit Dt. Weidelgras) sowie Nutzungsart (Schnitt, Brache) unterschieden. Die N2-Fixierungsleistungen dieser Bestände wurden parallel mit Differenzmethode, 15N-Verdünnungsmethode sowie natural-15N-abundance- Methode bestimmt. Wobei die Berechnungen jeweils alternativ mit und ohne Berücksichtigung der N-Mengen in den nicht erntbaren Pflanzenteilen durchgeführt wurden. Neben den Bewirtschaftungsfaktoren im Feld, zeigte auch die Wahl der Bestimmungsmethode einen bedeutenden Einfluss auf die Höhe der ermittelten N2-Fixierungsleistungen. Besonders die Nichtberücksichtigung der N-Mengen im nicht erntbaren Pflanzenmaterial führte zu einer deutlichen Unterschätzung der ermittelten N2-Fixierung

Evaluating a workspace's usefulness for image retrieval

Image searching is a creative process. We have proposed a novel image retrieval system that supports creative search sessions by allowing the user to organise their search results on a workspace. The workspace’s usefulness is evaluated in a task-oriented and user-centred comparative experiment, involving design professionals and several types of realistic search tasks. In particular, we focus on its effect on task conceptualisation and query formulation. A traditional relevance feedback system serves as a baseline. The results of this study show that the workspace is more useful in terms of both of the above aspects and that the proposed approach leads to a more effective and enjoyable search experience. This paper also highlights the influence of tasks on the users’ search and organisation strategy