Linked open data tools have been implemented through data.bnf.fr , a project which aims at making the BnF data more useful on the Web. data.bnf.fr gathers data automatically from different databases on pages about authors, works and themes. Online since July 2011, it is still under development and has feedbacks from several users, already. First the article will present the issues linked to our data and stress the importance of useful links and of persistency for archival purposes. We will discuss our solution and methodology, showing their strengths and weaknesses, to create new services for the library. An insight on the ontology and vocabularies will be given, with a “business” view of the interaction between rich RDF ontologies and light HTML embedded data such as schema.org . The broader question of Libraries on the Semantic Web will be addressed so as to help specify similar projects.