The PROBADO framework allows integration of content-based indexing and retrieval methods for multimedia documents for Digital Library applications. The PROBADO architecture follows a three layer approach which consists of a repository layer, a core system layer, and a presentation layer (cf. the diagram right). Distributed local repositories implement document-type specific indexing and accessing techniques, including rich meta data models. The PROBADO core layer keeps track of all document repositories registered in the system. It maintains an integrated index of all documents. The presentation layer offers rich user access methods, including graphical query specification, and document visualization. PROBADO defines a system protocol based on Webservice technology. It allows dispatching content-based and metadata-based user queries to local repositories, which manage the primary documents. Synchronization methods allow the repositories to inform the core system about availability and updates of hosted contents.
The PROBADO approach is flexible in that it allows connecting any specialized document repository that implements the PROBADO protocol to the system. While the current reference implementation supports 3D architectural and music documents, other document types can be integrated seamlessly. A key advantage offered by this approach is that added-value services such as user recommendation, relevance feedback, right management, and result set visualization are provided as a system service that is available to any integrated repository. Thereby, the approach is highly scalable.