The emerging use of semantic interoperability in digital library services is the hot topic since 2-3 decades. The paper discusses in terms of contexts and the information life-cycle; the role of semantic services. It discusses the Application and Relation of knowledge organization systems (KOS) with library. The paper discusses ontologies as well as the Role of Semantic Services and Semantic Description of Web Services. It highlights the processes to Enhance Semantic Interoperability and Current Developments. It highlights the Levels of Semantic Interoperability in Digital Library Environments and Data structures. Web Service Modeling Framework (WSMF) is also explained. 

Keyword: Semantic interoperability; Digital Library Environments; Ontologies; Data structures.