Advanced information technology is pervasive in any kind of human activity - science, business, finance, management and others - and this is particularly true for database systems. Both database theory and database applications constitute a very important part of the state of the art of computer science. Meanwhile there is some discrepancy between different aspects of database activity. Theoreticians are sometimes not much aware of the real needs of business and industry; software specialists not always have the time or the apportunity to get acquainted with the most recent theoretical ideas...