1. Semantic mapping involves connecting metadata structures like schemas and ontologies, as well as connecting vocabularies of values like knowledge organization systems and knowledge bases. 2. Significant progress has been made in mapping metadata structures to enable interoperability and data integration, though mapping knowledge organization systems remains a challenge due to the sparseness of links between concepts. 3. While automatic mapping tools have improved, manual mapping remains important and applications of mappings could be better categorized to inform mapping requirements and evaluation.