Nowadays, in Digital Libraries, non-textual and multimedia documents are indexed and accessed based on textual meta data. This kind of meta data is expensive to obtain, and in many cases, the content cannot be described completely and free of ambiguities. The project PROBADO aims to overcome these limitations by developing content-based access and presentation methods for specific, selected types non-textual documents. This goal is important due to the ever increasing amount of non-textual documents and the demand for novel accessing methods by users in the R&D and academic domains. PROBADO addresses the following Digital Library challenges:

• Easy integration into existing library workflows
• Persistent accessibility of documents by supporting persistent identifiers such as DOI
• Simplified integration of external non-textual document repositories
• Extensibility of the developed services for other engineering and technical disciplines and other document types
• Modular and service-oriented system architecture