Ein System zur Präsentation und Visualisierung von Linked Open Data in Webseiten mittels Semantic Data Widgets
Stegemann, T. (2022). [PhD thesis, University of Duisburg-Essen].
PhD thesis by Timo Stegemann
Abstract
The amount of publicly available linked data has been growing steadily since the beginning of the Semantic Web at the start of the 21st century. With over 200 billion relations, the Linked Open Data Cloud, in which various data sets are gleaned, comprises an inconceivable treasure trove of knowledge that can be freely accessed by every Internet user. However, even though this data is “public” and “free”, this does not mean that it can also be used by everyone. The enormous complexity of the technologies, applications and formats required for using this data, prevents the majority of Internet users from participating in this knowledge. This dissertation addresses the aforementioned problem and describes the Semwidg tool suite. Its goal is to provide easy access to this data, at least for users with knowledge of web technologies but without expertise in Linked Data, and thus to promote multiple use (Content-Syndication) of Linked Data content. Semwidg is a system for presenting and visualizing Linked Open Data in web pages using Semantic Data Widgets. These widgets encapsulate database queries and presentation-relevant information needed to retrieve data from the Linked Open Data Cloud, process it, and then display it within web pages. Semwidg consists of the three subcomponents SemwidgQL, SemwidgJS and SemwidgED. SemwidgQL is an easy-to-learn path query language that is adapted to the background knowledge of web developers and programmers in terms of its syntax and semantics. It can be transcompiled on the client-side into SPARQL, the de facto standard query language of Linked Data content. Based on two studies, it has been shown that SemwidgQL is easier to learn than SPARQL and can be used effectively and efficiently. SemwidgJS is a JavaScript widget library for presenting and visualizing Linked Data in web pages. It provides the usual web UI elements for output and input, as well as charts and maps, through a set of predefined widget classes. The widgets can exchange data with each other, allowing interactive web pages to be created. Furthermore, SemwidgJS is a framework that allows to define custom widget classes with just a few lines of JavaScript code. SemwidgED is an online WYSIWYG editor that supports users in embedding SemwidgJS widgets in web pages and formulating SemwidgQL queries. The usability of SemwidgED was evaluated in an empirical user study with respect to effectiveness, efficiency and user satisfaction. SemwidgED achieved very good results within the relevant target group.
