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While collaboration, negotiation, and consensus represent an integral part of ontology engineering processes, it is only recently that disciplined tools and infrastructure for collaborative ontology engineering have emerged. Tools such as Collaborative Protégé (Tudorache, Noy, Tu, & Musen, 2008) not only provide an infrastructure for collaboration and coordination, but also provide a structured log of all ontological changes, which users have made via the tool. These logs can, for example, include records of concepts added, properties changed, or relationships qualified. In aggregation, such logs can essentially capture the entire evolution of an ontology from its inception to its final stages on a very fine-grained level. At the same time, the availability of fine-grained logs poses new challenges and opportunities for studying and analyzing the history of collaborative ontology engineering projects. While there exists a plethora of visualization tools for ontologies, they have primarily been built to visualize aspects of the final product (the ontology) and not the collaborative processes behind construction (e.g. the changes made by contributors over time). To the best of our knowledge, there exists no ontology visualization tool today that focuses primarily on visualizing the creation processes behind collaboratively constructed ontologies.
This application paper sets out to present a visualization tool that primarily focuses on visualizing pragmatic aspects of collaborative ontology engineering, i.e. the social processes that yield collaboratively constructed ontologies. We present a tool – PragmatiX – that taps into structured log of changes provided by tools such as Collaborative Protégé and visualizes them via network-based and other kinds of visualizations. The tool is aimed at managers and leaders of collaborative ontology engineering projects to help them in monitoring progress, exploring issues and problems, and tracking quality-related issues such as overrides and coordination among contributors. PragmatiX is the successor of iCAT Analytics (Pöschko, Strohmaier, Tudorache, Noy, & Musen, 2012) and provides additional functionality such as the heat-map (as described in Section Concept Network Visualization), the possibility of importing multiple data sets into one instance of our tool, the support for multi-language data sets (see Section Category and Author Views) as well as various statistical overview pages such as the dashboards (see Section Dashboard). Additionally, a heuristic evaluation has been performed on our tool, providing interesting results for future work.
Our initial prototype demonstrates its capabilities by tapping into change-logs produced by variants of Collaborative Protégé, where changes and notes as well as comments on changes are represented in the Change and Annotation Ontology (ChAO) (Noy, Chugh, Liu, & Musen, 2006). Because several large collaborative ontology-engineering projects in the bio-medical domain use Collaborative Protégé (and its derivatives) for tool support, we have access to change-log data from a series of different projects. For example, the International Classification of Diseases (ICD-11) project uses WebProtégé, a Web version of Protégé that is built on the collaborative framework of Collaborative Protégé, to collaboratively engineer a bio-medical ontology consisting of more than 30,000 concepts (Tudorache, Falconer, Nyulas, Noy, & Musen, 2010). Almost all changes to this ontology have been captured and are available for further analysis. The International Classification of Traditional Medicine (ICTM) ontology represents another example, where a sufficiently large record of changes is available. In this paper, we will use data from these two projects to demonstrate the general applicability of our tool for visualizing pragmatic aspects of collaborative (ontology-) engineering projects. While the illustrations in this paper are limited to these two projects, there is nothing in our implementation, which prevents other collaborative ontology engineering projects (e.g. outside the bio-medical domain) being visualized with our tool in a similar manner, given that data about the creation process is available in a structured form (see section Implementation).