Skip to content
Switch branches/tags

Latest commit


Git stats


Failed to load latest commit information.
Latest commit message
Commit time


Competency question Language for specifying Requirements for an Ontology and similar artefacts


Competency Questions (CQs) for an ontology aim to demarcate the scope of its contents. They are sparsely used in ontology development, however, likely because there is no tooling and automation for writing them and evaluating them against the ontology, therewith hampering their effective use. Regarding support for authoring CQs, there are a few question templates based on informal analyses of a small number of competency questions, hence, with limited coverage of question types and sentence constructions. No Controlled Natural Language exists to guide the domain experts to author CQs.

We aim to fill this gap by proposing the CLaRO template-based Controlled Natural Language resource to author CQs. For its design, we exploited a new dataset of 234 TBox-level CQs that had been analysed automatically into 106 patterns, which we analysed on their shape, commonalities, and recurring patterns, which was subsequently used to design a template-based CNL, with an additional XML serialisation. The templates also are annotated with a set of human-friendly aspects so that a user may select, e.g., "a CQ template that asks for difference" to narrow down formulating a CQ.

The CNL was evaluated with a subset of questions from the original dataset and with two sets of newly sourced competency questions. The coverage of CLaRO, with its 93 main templates and 41 linguistic variants, is about 90% for unseen questions. CLaRO has the potential to facilitate streamlining formalising ontology content requirements and, given that about one third of the competency questions in the test sets turned out to be invalid questions, assist in writing good questions.

Resources on this github repo

This repository has the following resources:

  • the 134 templates of CLaRO, in xml and in txt
  • the data and results of the CLaRO evaluation
  • a data file with annotations how CLaRO was created
  • a tool to author questions using the CLaRO templates
  • The newly collected CQs and rewritten CQs for CLaRO v2
  • The result of the evaluation with cleaned CLaRo and CLaRO v2
  • The CLaRO v2 templates

Demo of the CLaRO tool (v1)

Click on the image to start the video

Demo video of the tool

Citing CLaRO

Version 1: Keet, C.M., Mahlaza, Z., Antia, M.-J. CLaRO: a Controlled Language for Authoring Competency Questions. 13th Metadata and Semantics Research Conference (MTSR'19). E. Garoufallou et al. (Eds.). Springer CCIS vol. 1057, 3-15. 28-31 Oct 2019, Rome, Italy. published version at Springer

Version 2: Antia, M.-J., Keet, C.M. Assessing and Enhancing Bottom-up CNL Design for Competency Questions for Ontologies. 7th International Workshop on Controlled Natural language (CNL’21), 8-9 Sept. 2021, Amsterdam, the Netherlands. (in print)

Availability for use and reuse

CLaRO is available under a CC-BY licence


Competency question Language for specifying Requirements for an Ontology



No releases published


No packages published