MOSS as a Multimedia - Object Server – Extended Summary –

Today, most multimedia (MM) applications store their data objects in a proprietary way, usually in files on some storage device in some format that is tailored exactly to the necessities of this one application. But MM data objects (MMOs) are expected to exist for long periods of time and to be accessed by many different applications. Additionally, the employment of new opportunities offered by the technical progress (new media, devices etc.) must be possible. The demands for application neutrality (application-independent data management) and data independence (abstraction from different storage formats, compression techniques and storage devices) are obvious. Database management systems (DBMSs) have been identified as the ideal means to guarantee these issues. The integration of MMOs into these systems leads to multimedia DBMSs (MMDBS) [Meye91]. The design of a MMDBS can be based mainly on two kinds of DBMSs: extensible relational systems of different flavors [Bato90, Care92, Stone87] and object-oriented DBMS [Kim90]. All existing systems, even if they are designed for complex objects, use only conventional datatypes or bit fields with no semantics defined on them in form of special operations [Kaec93]. The storage and retrieval of MMOs demands for flexible mechanisms to incorporate new storage techniques and devices which are only partially available in these systems. Other important issues are the development of novel, medium-specific access paths for MMOs that reflect the semantically rich contents of MMOs and the design of generalized interfaces for the MMOs. The multimedia object storage system (MOSS) designed at the University of Erlangen is a standalone system that allows to focus on the questions related to the storage and retrieval of MMOs. MOSS has a highly modular structure, which is ideal to compare different solutions for the issues mentioned above. Furthermore, it is integrated in a client-server architecture.