Abstract Current XML database systems largely neglect or make limited use of available schema definitions. But only with schema definitions at hand is it possible to ensure database consistency by document validation, to store, index, and access the content of elements and attribute values in an appropriately typed manner and not just as text, and to perform more sophisticated query optimizations. In this paper, we give an overview of our implementation of a schema‐aware XML database system: the Persistent Typed Document Object Model (PTDOM). Originally developed for the management of MPEG‐7 media descriptions in a database, the core of PTDOM is made up of a schema catalog capable of managing schema definitions written in MPEG‐7 DDL, a superset of XML schema. PTDOM exploits the schema information maintained by this catalog in a variety of contexts: for document validation, for typed storage of elements and attribute values, for structural indexing of XML documents providing additional efficient access paths to document contents, and for optimized construction of query execution plans for XPath expressions. This along with its profound extensibility with new datatypes, user‐defined functions, and value index structures makes PTDOM a flexible and effective database solution not only for the management of MPEG‐7 media descriptions but also for the management of any kind of XML documents for which schema definitions exist. Copyright © 2006 John Wiley & Sons, Ltd.

introduction Share on Introduction to special issue on the use of context in multimedia information systems Authors: K. Selçuk Candan Arizona State University Arizona State UniversityView Profile , Augusto Celentano Ca' Foscari University of Venice Ca' Foscari University of VeniceView Profile , Wolfgang Klas University of Vienna University of ViennaView Profile Authors Info & Claims ACM Transactions on Multimedia Computing, Communications, and ApplicationsVolume 2Issue 3August 06 pp 173–176https://doi.org/10.1145/1152149.1152150Published:01 August 2006Publication History 0citation826DownloadsMetricsTotal Citations0Total Downloads826Last 12 Months2Last 6 weeks1 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my Alerts New Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access

Existing multimedia streaming technologies offer no specific support for user interaction like jumping to bookmarks in a video, or switching to reverse play. When the users, e.g., jump to a bookmark, the player requests frames for the new presentation point from the server and resumes playing only when the data has arrived. Our solution for this problem is the client prefetching the buffering strategy, MPEG-L/MRP, that ensures that the frames which are needed for a response to a possible user interaction are already in the client's buffer, which leads to qucik and smooth reaction to user interactions. In case of variable bandwidth, our MPEG-1 streaming approach selects only a subset of all frames to be fetched from the server and supports a smooth presentation at a reduced frame rate with correct timelines.The technical demonstration shows the interactive streaming of MPEG-videos and illustrates our buffering and prefetching strategy.

Advanced multimedia applications require adequate support for the modeling of multimedia content by multimedia document models. More and more this support calls for not only the adequate modeling of the temporal and spatial course of a multimedia presentation and its interactions, but also for the partial reuse of multimedia documents and adaptation to a given user context. However, our thorough investigation of existing standards for multimedia document models such as HTML, MHEG, SMIL, and HyTime leads to us the conclusion that these standard models do not provide sufficient modeling support for reuse and adaptation. Therefore, we propose a new approach for the modeling of adaptable and reusable multimedia content, the Z/sub Y/X model. The model offers primitives that provide-beyond the more or less common primitives for temporal, spatial, and interaction modeling-a variform support for reuse of structure and layout of document fragments and for the adaptation of the content and its presentation to the user context. We present the model in detail and illustrate the application and effectiveness of these concepts by samples taken from our Cardio-OP application in the domain of cardiac surgery. With the Z/sub Y/X model, we developed a comprehensive means for advanced multimedia content creation: support for template-driven authoring of multimedia content and support for flexible, dynamic composition of multimedia documents customized to the user's local context and needs. The approach significantly impacts and supports the authoring process in terms of methodology and economic aspects.

Adaptation techniques for multimedia presentations are mainly concerned with switching between different qualities of single media elements to reduce the data volume and by this to adapt to limited presentation resources. This kind of adaptation, however, is limited to an inherent lower bound, i.e., the lowest acceptable technical quality of the respective media type. To overcome this limitation, we propose cross-media adaptation in which the presentation alternatives can be media elements of different media type, even different fragments. Thereby, the alternatives can extremely vary in media type and data volume and this enormously widens the possibilities to efficiently adapt to the current presentation resources. However, the adapted presentation must still convey the same content as the original one, hence, the substitution of media elements and fragments must preserve the presentation semantics. Therefore, our cross-media adaptation strategy provides models for the automatic augmentation of multimedia documents by semantically equivalent presentation alternatives. Additionally, during presentation, substitution models enforce a semantically correct information flow in case of dynamic adaptation to varying presentation resources. The cross-media adaptation strategy allows for flexible reuse of multimedia content in many different environments and, at the same time, maintains a semantically correct information flow of the presentation.

A novel database system service called a playout management service, which performs multimedia presentations was proposed by the authors recently [1st Int. Workshop on Multimedia Database Mgmt. Systems, pp. 38-47, 1995]. In distributed multimedia database systems without end-to-end guarantees, such a playout management service faces the potential problem that system performance can become insufficient when realizing a stored presentation. This problem can be overcome by making the playout management service reactive, such that it balances the amount of data to be fetched from a remote multimedia database with the system performance that is available. For the users, this means that a running presentation is adapted by the playout management service. In this paper, we propose the concept of a /spl delta/-set to adapt the execution of arbitrary multimedia presentations in an optimized way. We present a heuristic scheme to identify the most adequate /spl delta/-set with respect to (1) the actual system state, (2) the user preferences, and (3) the specific properties of multimedia presentations.

The part-whole semantic relationship (the part relationship, for short) is an important modeling primitive in many advanced application domains such as manufacturing, design, and document processing. In this paper, we examine the problem of integrating such a construct into an OODB system. Specifically, two questions are addressed in this regard. This first is: Can a part relationship be made an intrinsic construct of an existing OODB system without having to rewrite a substantial portion of the system? The second: Can an “open” OODB system which claims to support such an integration really do so, and, more specifically, can the integration be done using a metaclass mechanism which purports to bring extensibility to the VODAK Model Language (VML)?