Decision Support Systems provide knowledge and knowledge processing capacity essential for referral decision situations and decision-making, improving decision-making and decision-making results and relaxing the cognitive, temporal, spatial and economic limits of the decision-makers. Libraries and librarians support in decisionsmaking varied in time from a passive, traditional collections of books and journals, to some highly active, decision assistants. Digital libraries have provided new insights for corporate decision support systems. Data mining techniques have become crucial for the management, organization and dissemination of information to the right users at the right time. Bibliomining provides the opportunity through a single data warehouse to compile knowledge on the interconnections between different social networks, the community of authors and the community made up of the library and its users. Library decision support system tends to become a naturally important actor in the supply of knowledge to companies decision support systems. The article focuses on a formal approach to building a library decision support system.