Life science ontologies have become increasingly important within the recent years. Typically, they are utilized to semantically describe molecular-biological objects in a common and uniform way, e.g., proteins are annotated with concepts of the well-known Gene Ontology to specify their molecular functions and biological processes in which they are involved. However, they underlie continuous changes since new research results become available or existing knowledge need to be revised. Therefore, it is valuable to study what and how many changes occur in order to assess an ontology’s stability and impact on available annotations.
We present OnEX (Ontology Evolution Explorer - http://www.izbi.de/onex) that currently provides access to approx. 500 versions of 16 life science ontologies. Particularly, OnEX allows for a systematic exploration of changes in ontologies using two main workflows. On the one hand, the “Evolution Trend Workflow” quantifies ontology statistics and changes comparatively, e.g., by generating evolution trend charts for concepts and relationships. Furthermore, each evolution step (ontology version change) can be analyzed in more detail by inspecting added, deleted, fused or obsolete concepts. On the other hand, the “Concept Evolution Workflow” provides an evolution analysis for ontology concepts. Users are able to search for concepts across all ontologies using specified keywords. For located concepts it is possible to display all up-to-date and first version attributes with their values but also evolution-related information, e.g., creation date and changes on attributes (add, delete, change of values).