efficiently store network structured data. But while plenty of research has gone into the development of this technology, querying for a subset of the data is lacking user friendly interfaces. Of the two main query methods, graph pattern matching and graph traversal, the first has received more attention and more methods providing visual support in querying are available. The latter, graph traversal, while being very powerful, has seen little advances in visual querying. This thesis aims at providing a novel user interface for graph traversal query formulation - a visual query language for graph databases - entitled Pygmalion Query. In the thesis, first a literature review is undertaken to discover any previous approaches taken at such a visual query language. With it, gaps in the currently available research are identified. Following the literature review, needs and requirements are identified from different sources, such as queries posted online and documentation for graph traversal query languages. After selection of minimum required features, the design for Pygmalion Query is created. A web-based implementation, built on available frameworks, is implemented. Following the creation of Pygmalion Query, a twofold evaluation is conducted. An expert review serves as the initial confirmation of the approach taken. Using feedback coming from the experts, an updated implementation is created. A small comparative user study is carried to test for usability. The results of the expert review and user study indicate a positive usability effect of Pygmalion Query in the formulation of graph traversal queries over the currently available solutions. The participants of the study, in greatest part novice users, are more likely to complete the tasks posed to them with the visual query language.
Query Language
Currently, users who want to perform a complex analysis on graph data are dependent on knowledge about the data and complex command line interfaces. In order to simplify the complex analysis of graph data, appropriate tools have to be provided. Visual interaction increases the information content while at the same time it reduces the cognitive load on the user and supports him during query formulation. Numerous different approaches in literature make use of this fact. They reach from simple interactive visualization models to domain-specific visual query languages, but also reveal that there are some very similar developments to the proposed system. However, the combination of both aspects, i.e. the provision of an integrated system, allowing for graphically formulating complex queries and simultaneously supporting the user with visualizations could not be found in the literature. Hence the design of such a system makes a significant contribution to the research and development of graph databases. In this Thesis a design for such a system is developed with help of the query language for graph databases Gremlin and using a visual block metaphor. Based on this a prototype is implemented and evaluated.