This paper proposes a methodological approach to CLIR applications for the development of a system which improves multi-word processing when specific domain translation is required. The system is based on a multilingual ontology, which can improve both translation and retrieval accuracy and effectiveness. The proposed framework allows mapping data and metadata among language-specific ontologies in the Cultural Heritage (CH) domain. The accessibility of Cultural Heritage resources, as foreseen by recent important initiatives like the European Library and Europeana, is closely related to the development of environments which enable the management of multilingual complexity. Interoperability between multilingual systems can be achieved only by means of an accurate multi-word processing, which leads to a more effective information extraction and semantic search and an improved translation quality.