  The Simple Knowledge Organization System (SKOS) is popular for expressing
controlled vocabularies, such as taxonomies, classifications, etc., for their
use in Semantic Web applications. Using SKOS, concepts can be linked to other
concepts and organized into hierarchies inside a single terminology system.
Meanwhile, expressing mappings between concepts in different terminology
systems is also possible. This paper discusses potential quality issues in
using SKOS to express these terminology mappings. Problematic patterns are
defined and corresponding rules are developed to automatically detect
situations where the mappings either result in 'SKOS Vocabulary Hijacking' to
the source vocabularies or cause conflicts. An example of using the rules to
validate sample mappings between two clinical terminologies is given. The
validation rules, expressed in N3 format, are available as open source.
