We present several extensions of the explanation facility of the ontology editor Protege. Currently, explanations of OWL entailments in Protege are provided as justifications-minimal subsets of axioms that entail the given axiom. The plugin called 'explanation workbench' computes justifications using a black-box algorithm and displays them in a convenient way. Recently, several other (mostly glass-box) tools for computing justifications have been developed, and it would be of interest to use

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... h tools in Protege. To facilitate the development of justification-based explanation plugins for Protege, we have separated the explanation workbench into two reusable components-a plugin for blackbox computation of justifications and a plugin for displaying (any) justifications. Many glass-box methods compute justifications from proofs, and we have also developed a reusable plugin for this service that can be used with (any) proofs. In addition, we have developed an explanation plugin that displays such proofs directly. Both plugins can be used, e.g., with the proofs provided by the ELK reasoner. This paper describes design, features, and implementation of these plugins.