Considers the problem of querying multimedia presentations based on content information. Multimedia presentations are modeled as presentation graphs, which are directed acyclic graphs that visually specify the presentations. We present a graph data model for the specification of multimedia presentations and discuss query languages as effective tools to query and manipulate multimedia presentation graphs with respect to content information. To query the information flow throughout a multimedia presentation, as well as in each individual multimedia stream, we use revised versions of temporal operators Next, Connected and Until, together with path formulas. These constructs allow us to specify and query paths along a presentation graph. We present an icon-based graphical query language, GVISUAL, that provides iconic representations for these constructs and a user-friendly graphical interface for query specification. We also present an OQL-like language, GOQL (Graph OQL), with similar constructs, that allows textual and more traditional specifications of graph queries. Finally, we introduce GCalculus (Graph Calculus), a calculus-based language that establishes the formal grounds for the use of temporal operators in path formulas and for querying presentation graphs with respect to content information. We also discuss GCalculus/S (GCalculus with Sets) which avoids highly complex query expressions by eliminating the universal path quantifier, the negation operator and the universal quantifier. GCalculus/S represents the formal basis for GVISUAL, i.e. GVISUAL uses the constructs of GCalculus/S directly.

This paper describes SciMMDB, a scientific multimedia database system designed for polymer science experiment data applications. SciMMDB maintains multimedia data types of video, test and picture (as well as other standard data types), and allows users to: form multimedia presentation streams about experiments; define a presentation which organizes a number of presentation streams for playout purposes; and control the playout of a presentation. To form video, text or picture streams, a presentation stream construction language is described. Queries in this language express spatial and temporal relationships involving content objects and efficient evaluation of such queries are facilitated by indexing structures. SciMMDB uses IB+trees for queries involving temporal intervals. In SciMMDB, presentation streams are formed into a presentation using the notion of presentation graphs. During the playout of a presentation, each presentation stream in the presentation is played out by a separate transaction, called an output agent. Such transactions communicate and synchronize with each other using the cooperative transaction model.