OntospyWeb is a tool made for navigating ontologies ('vocabularies') encoded using the RDF family of languages. It is based on the Ontospy Python library, which in turns wraps RDFLib.
A. Polleres, A. Hogan, R. Delbru, and J. Umbrich. Reasoning Web: Semantic Technologies for Intelligent Data Access, volume 8067 of Lecture Notes in Computer Science, Springer, Heidelberg, (2013)