Thesaurus alignments for semantic interoperability in the National Library of the Netherlands (KB) library domains is evaluated by three participating systems, such as Falcon, DSSim, and Silas. Ontology Alignment Evaluation Initiative (OAEI) 2007 Library Track was taken as the evaluation context and evaluation were conducted by Simple Knowledge Organization System (SKOS) mapping relations. Better interoperability and reduction of costs is achieved by scenarios such as reindexing, concept-based search across vocabularies, navigation across thesauri, and thesaurus merging. The required thesaurus alignments needed to specify a function that translates the concepts of a GTT-indexed book into Brinkman concepts to yield a Brinkman indexing of the book. It was required a single access point to multiple collections, each of which is described by a different thesaurus.