One of the main library network function is so-called shared cataloguing, i.e. the exchange of bibliographic records on national and international level. In this paper we present a system for creating valid bibliographic records based on XML technology, as a basis for exchange of these records within default library network. To perform the exchange of XML bibliographic records it is necessary to ensure these records be valid against the adopted document type definition. The validation will be done against a schema written in XML Schema Language, based on the international standard for recording the bibliographic data in machine-readable cataloguing format - UNIMARC. The system for creating valid XML bibliographic records will be implemented in Java environment.