  Developments in semantic web technologies have promoted ontological encoding
of knowledge from diverse domains. However, modelling many practical domains
requires more expressiveness than what the standard description logics (most
prominently SROIQ) support. In this paper, we extend the expressive DL SROIQ
with constraint networks (resulting in the logic SROIQc) and grounded
circumscription (resulting in the logic GC-SROIQ). Applications of constraint
modelling include embedding ontologies with temporal or spatial information,
while those of grounded circumscription include defeasible inference and closed
world reasoning.
  We describe the syntax and semantics of the logic formed by including
constraint modelling constructs in SROIQ, and provide a sound, complete and
terminating tableau algorithm for it. We further provide an intuitive algorithm
for Grounded Circumscription in SROIQc, which adheres to the general framework
of grounded circumscription, and which can be applied to a whole range of
expressive logics for which no such specific algorithm presently exists.
