CARNet Media on Demand (MoD) service aims to provide Croatian academic and research community with tools, resources and knowledge needed for implementation of multimedia technologies in research and educational process. Paper will mostly discuss the architecture and operation of MoD server system and it's XML-based metainformation model which provides content-authors with friendly and usable interface for Web-based management of their content and provides end users with easy and transparent access to various formats of multimedia content. Various implementations of metainformational model for multimedia content will also be discussed in order to clarify some decisions taken during the development of content description and management model and tools implemented in CARNet MoD service and server system.