Accessing structured data in the form of ontologies currently requires the use
of formal query languages (e.g., SeRQL or SPARQL) which pose significant
difficulties for non-expert users. One way to lower the learning overhead
and make ontology queries more straightforward is through a Natural Lan-
guage Interface (NLI). While there are existing NLIs to structured data
with reasonable performance, they tend to require expensive customisation
to each new domain. Additionally, they often require specific adherence to
a pre-defined syntax which, in turn, means that users still have to undergo
training.
In this thesis, we study the usability of NLIs from two perspectives: that of
the developer who is customising the NLI system, and that of the end-user
who uses it for querying. We investigate whether usability methods such
as feedback and clarification dialogs can increase the usability for end users
and reduce the customisation effort for the developers. To that end, we have
developed two systems, QuestIO and FREyA, whose design, evaluation and
comparison with similar systems form the core of the contribution of this
thesis
