A logic-based reasoning system is a software system that generates conclusions that are consistent with a knowledge base (KB) or ontology. However, because the steps taken to generate a conclusion are usually hidden from the user, it cannot be guaranteed that the user accepts and acts upon the conclusion[3]. This leads to systems that provide explanations and justi cations as a key part of the system's design[5]. Novice and expert users greatly bene t from explanations[1].
C. Pretorius & T. Meyer
If a formal de nition or AnnotationProperty is added to the OWL standards, then the de nition used in this paper will be changed to re ect the OWL standards. Explanations are still invoked when the user clicks on the \Explain inference" button that appears next to each axiom. Checkboxes are added to allow the user to decide if annotated explanations should be displayed or keywords expanded. Users are allowed to have the checkboxes checked in any combination. If neither is checked, the output is exactly as the original Explanation Workbench would produce.
Keyword expansion is implemented as a single function. The function iterates through the axiom and replaces every keyword with the equivalent expansion. It returns the expanded axiom to the renderer to be displayed on the screen. If the checkbox for explanatory annotations is checked, the method checks if the axiom has any annotations attached to it. If there is at least one annotation, it iterates over all annotations and checks if any annotation has the annotation property \exp:Explanation". If this is true, the renderer will display the axiom (in its original Manchester Syntax form) and append the explanatory annotation after it. Note that this functionality requires the ontology creator to have de ned the explanatory annotations beforehand.
The source code of this extension of the Explanation Workbench can be found and freely downloaded from the paper's GitHub repository3. It will require Protege to be of use, which can be downloaded from protege.stanford.edu. The More Readable Extension to the Explanation Workbench (MRE) is of signi cant value to novice users since it allows them to more easily understand description logics and the knowledge held by the ontology. It does not prohibit the more rigid and formal notation, thereby bene ting expert users who might prefer the more formal notation. It can allow all users to receive terminological knowledge regarding the ontology with signi cantly greater ease and is therefore of great bene t to users wanting to familiarise themselves with a new ontology.
The next step in this research would be to create a tool to automatically generate the explanatory annotations for axioms. This research could draw inspiration from OWL Simpli ed English (OWLSE) and Attempto Controlled English (ACE) to formulate the actual annotations. It might also look at Horridge's work on justi cations to determine what axioms should get annotations if annotations are prioritised to the most important axioms. Further research can also be done to integrate the keyword expansion and the OWLSE and ACE syntaxes. This can be integrated with user testing to evaluate the various attempts at natural language expressions for OWL and the associated explanations. 3 https://github.com/Pietersielie/Explanation-Workbench-More-Readable-Extension Improved explanations in the Protege OWL ontology editor