This book constitutes the ?rst volume of the ?rst journal in the new LNCS Jo- nal Subline, the Journalon Data Semantics. Publishingajournalinabookseries might come as a surprise to customers, readers, and librarians, thus we would like to provide some background information and our motivation for introducing this new LNCS subline. As a consequence of the very tight interaction between the Lecture Notes in Computer Scienceseriesandtheinternationalcomputerscienceresearchand- velopment community, we receive quite a few proposals for new archive journals. From the successful launch of workshops or conferences and publication of their proceedings in the LNCS series, it might seem like a natural step to approach the publisher about launching a journal once this speci?c ?eld has gained a c- tain level of maturity and stability. Each year we receive about a dozen such proposals and even more informal inquiries. Like other publishers, it has been our experience that launching a new jo- nal and making it a long-term success is a hard job nowadays, due to a generally di?cult market situation, and library budget restrictions in particular. Because many of the proceedings in LNCS, and especially many of the LNCS postp- ceedings, apply the same strict reviewing and selection criteria as established journals, we started discussing with proposers of new journals the alternative of devoting a few volumes in LNCS to their ?eld, instead of going through the painful Sisyphean adventure of establishing a new journal on its own.