Thorsten Vitt

TextGrid and eHumanities

TextGrid is a new Grid project in the framework of the German D-Grid initiative, with the aim to deploy Grid technologies for humanities scholars working on historical (German) texts. Its two roots, humanities computing and eScience (Grid computing used by research together with modern communication technologies), are the basis for TextGrid to provide pioneer work in eHumanities. After summarizing Humanities Computing and modern network technologies, community expectations in the fields of philological edition and other application areas are set forth, from which functional requirements such as modularity, distribution, etc. are distilled. The first version of the TextGrid architecture was designed in accordance with these requirements, and focuses on openness by standard conformance and encapsulation. It provides storage Grid services via a pure Web Services interface to dedicated Web Services tools for different aspects of text processing, analysis and retrieval. This platform aims to provide easily usable tools for scholars, but also specifies interfaces for external program developers to add functionality.

Open ehumanities digital ecosystems and the role of resource registries

The last few years have seen a massive push towards collaborative working methods in the humanities. Many large and small eHumanities Digital Ecosystems (DEs) have sprung into existence. The big challenge ahead is now to see how these subsystems can begin to merge into one larger eHumanities DE while still maintaining their individual characters and strengths. Starting out from a presentation of TextGrid as an exemplary DE in the eHumanities, the article studies two prerequisites for successful interoperability between DEs in the field, namely loosely-coupled services and the visibility of resources. The authors then propose a reference ontology for eHumanities resources, both services and documents alike.

Understanding and explaining Delta measures for authorship attribution

This article builds on a mathematical explanation of one the most prominent stylometric measures, Burrows’s Delta (and its variants), to understand and explain its working. Starting with the conceptual separation between feature selection, feature scaling, and distance measures, we have designed a series of controlled experiments in which we used the kind of feature scaling (various types of standardization and normalization) and the type of distance measures (notably Manhattan, Euclidean, and Cosine) as independent variables and the correct authorship attributions as the dependent variable indicative of the performance of each of the methods proposed. In this way, we are able to describe in some detail how each of these two variables interact with each other and how they influence the results. Thus we can show that feature vector normalization, that is, the transformation of the feature vectors to a uniform length of 1 (implicit in the cosine measure), is the decisive factor for the improvement of Delta proposed recently. We are also able to show that the information particularly relevant to the identification of the author of a text lies in the profile of deviation across the most frequent words rather than in the extent of the deviation or in the deviation of specific words only. .................................................................................................................................................................................