QuaSAQ: A Database-Centric Approach to Enabling End-to-End Qos Control for Multimedia Repositories

The paper discusses the design and prototype implementation of a QoS aware multimedia database system. Recent research in multimedia databases has devoted little attention to the aspect of the integration of QoS support at the user level. One common scenario which we are concerned with connects a user through a visual interface to a multitude of media object stores. The user demands satisfiability of a set of quality parameter bounds specified at query time or before (via user profile mappings). The user is not aware of detailed low-level QoS parameters but rather specifies high-level, qualitative attributes on the media query. Our proposed architecture to enable end-ta-end QoS control, the QoS-Aware Query Processor (QuaSAQ), is motivated by query processing and optimization techniques in traditional database management systems. The proposed solution relies on mediation through several components (two of which are the QoP Browser and Quality Manager) that enable searching, locating, composing and presenting of multimedia objects with associated QoS constraints. In addition to an overview of key research issues, this paper also presents some of the proposed design solutions. One focus problem is how to evaluate the alternative plans for serving QoS-enhanced queries. We propose a novel cost model that explicitly takes the resource utilization of plans and the current system contention level into account. Experiments run on the QuaSAQ prototype show significantly improved QoS and throughput in media query processing.