Continuous Media Retrieval Optimizer for Hierarchical Storage Structures

One of the key components of multimedia systems is a Continuous Media server (CM server) that guarantees the uninterrupted delivery of continuous media data (e.g., video). Digital libraries and commercial broadcasting systems are sample applications that can ben-eet from such multimedia systems. Queries imposed by such applications might require the retrieval of one or more continuous objects stored on the CM server. Traditionally, multimedia systems have opted to guarantee that the CM server can display all the objects in the set to the user with no interruptions and with very strict timing among the display of these objects, resulting in a single retrieval plan. However, for a class of applications, we have observed that depending on the user query, user proole, and session proole, there are a number of exibilities that can be exploited for retrieval optimization. In (Shahabi et al., 1998), we presented a formal deenition for these exibilities and a description of a Proole Aware Retrieval Optimizer (Prime) that utilizes these exibilities to improve system performance. In this paper, we consider two extensions to Prime, namely: 1) Prime + : which uses memory buuering to alleviate fragmented server bandwidth, and 2) Prime : which is an extension of Prime for a hierarchical storage system. By means of a simulation study, we show that Prime and Prime + can signiicantly improve the system response time and/or other application speciic metrics (e.g., latency time).