In last years the amount of digital documents has increased dramatically. Unfortunately the same did not occur with the structure and organization of the information. Traditionally we built a digital library using a catalog with documents' meta-information including a conceptual classification and an ontology of concepts. In this document we present a set of modules to help in the task of building and maintaining a digital library. It includes a module to work with ontologies, a set of modules to handle specific catalog formats (like BibTeX), a module to define new catalog formats and a tool to integrate ontologies and multi-format catalogs in a web browse-able knowledge-base.