Planning future information services of a library, one has to balance the demand for advanced and the supply of appropriate services. While the second aspect requires to match the general state of the art with the specific skills of the library - especially but not only the skills of its employees - the first aspect requires the more challenging match of the "general" customer expectations with the "real" customer behavior. Of course, planning further services has to consider constraints in budget and other resources.

Therefore, libraries intending to successfully offer customized services need comprehensive information about their customers. They should know the customers' current library usage behavior, their needs and preferences, as well as the role and importance of available library services in the future. To gain this knowledge primary (e.g. library user surveys devoted to special topics) and secondary data sources (e.g. transaction recordings provided by the operative systems) can be used.

The presentation discusses requirements and conditions of implementing customer intelligence in modern libraries. In front of this background we develop a conceptual framework for a library information system based on a data warehouse approach that links external and internal data to support strategic planning processes. The presentation closes with an empirical example which demonstrates the usability of quantitative methods from marketing research for decision support in library management.