Log analysis can be a primary source ofkno wledge about how digital library patrons actually use DL systems and services and how systems behave while trying to support user information seeking activities. Log recording and analysis allow evaluation assessment, and open opportunities to improvements and enhanced new services. In this paper, we propose an XML-based digital library log format standard that captures a rich, detailed set of system and user behaviors supported by current digital library services. The format is implemented in a generic log component tool, which can be plugged into any digital library system. The focus of the work is on interoperability, reusability, and completeness. Specifications, implementation details, and examples of use within the MARIAN digital library system are described.