This LNCS journal series aims to provide a highly visible dissemination channel for remarkable work that in one way or another addresses research and development on issues related to data semantics. The target domain ranges from theories supporting the formal definition of semantic content to innovative domain-specific applications of semantic knowledge. We expect such a publication channel to be of highest interest to researchers and advanced practitioners working on the Semantic Web, interoperability, mobile information services, data warehousing, knowledge representation and reasoning, conceptual database modeling, ontologies, and artificial intelligence.We felt that producing a new journal on this theme was most appropriate at this time, considering the evolution of computer science and practice. Computerized information handling has recently changed its focus from centralized data management systems to decentralized data exchange facilities. Modern distribution channels, such as high-speed Internet networks and wireless communication infrastructures, provide reliable technical support for data distribution and data access, realizing the new popular idea that data may be available to anybody, anywhere, anytime. However, providing huge amounts of data on request often turns out to be a counterproductive service, making the data useless because of poor relevance or an inappropriate level of detail. Semantic knowledge is the essential missing piece that allows the delivery of information that matches user requirements. Semantic agreement, in particular, is essential to meaningful data exchange.Semantic issues have long been open topics in data and knowledge management. However, the boom in semantically poor technologies, such as the Web and XML, has excited renewed interest in semantics. For instance, conferences on the Semantic Web attract crowds of participants, while ontologies on their own has become a hot topic in the database and artificial intelligence communities.