  The extraction of logically-independent fragments out of an ontology ABox can
be useful for solving the tractability problem of querying ontologies with
large ABoxes. In this paper, we propose a formal definition of an ABox module,
such that it guarantees complete preservation of facts about a given set of
individuals, and thus can be reasoned independently w.r.t. the ontology TBox.
With ABox modules of this type, isolated or distributed (parallel) ABox
reasoning becomes feasible, and more efficient data retrieval from ontology
ABoxes can be attained. To compute such an ABox module, we present a
theoretical approach and also an approximation for $\mathcal{SHIQ}$ ontologies.
Evaluation of the module approximation on different types of ontologies shows
that, on average, extracted ABox modules are significantly smaller than the
entire ABox, and the time for ontology reasoning based on ABox modules can be
improved significantly.
