  Competency Questions (CQs) are natural language questions outlining and
constraining the scope of knowledge represented by an ontology. Despite that
CQs are a part of several ontology engineering methodologies, we have observed
that the actual publication of CQs for the available ontologies is very limited
and even scarcer is the publication of their respective formalisations in terms
of, e.g., SPARQL queries. This paper aims to contribute to addressing the
engineering shortcomings of using CQs in ontology development, to facilitate
wider use of CQs. In order to understand the relation between CQs and the
queries over the ontology to test the CQs on an ontology, we gather, analyse,
and publicly release a set of 234 CQs and their translations to SPARQL-OWL for
several ontologies in different domains developed by different groups. We
analysed the CQs in two principal ways. The first stage focused on a linguistic
analysis of the natural language text itself, i.e., a lexico-syntactic analysis
without any presuppositions of ontology elements, and a subsequent step of
semantic analysis in order to find patterns. This increased diversity of CQ
sources resulted in a 5-fold increase of hitherto published patterns, to 106
distinct CQ patterns, which have a limited subset of few patterns shared across
the CQ sets from the different ontologies. Next, we analysed the relation
between the found CQ patterns and the 46 SPARQL-OWL query signatures, which
revealed that one CQ pattern may be realised by more than one SPARQL-OWL query
signature, and vice versa. We hope that our work will contribute to
establishing common practices, templates, automation, and user tools that will
support CQ formulation, formalisation, execution, and general management.
