Wolfgang Klas

A survey of techniques for achieving metadata interoperability

Achieving uniform access to media objects in heterogeneous media repositories requires dealing with the problem of metadata interoperability. Currently there exist many interoperability techniques, with quite varying potential for resolving the structural and semantic heterogeneities that can exist between metadata stored in distinct repositories. Besides giving a general overview of the field of metadata interoperability, we provide a categorization of existing interoperability techniques, describe their characteristics, and compare their quality by analyzing their potential for resolving various types of heterogeneities. Based on our work, domain experts and technicians get an overview and categorization of existing metadata interoperability techniques and can select the appropriate approach for their specific metadata integration scenarios. Our analysis explicitly shows that metadata mapping is the appropriate technique in integration scenarios where an agreement on a certain metadata standard is not possible.

An analysis of XML database solutions for the management of MPEG-7 media descriptions

MPEG-7 constitutes a promising standard for the description of multimedia content. It can be expected that a lot of applications based on MPEG-7 media descriptions will be set up in the near future. Therefore, means for the adequate management of large amounts of MPEG-7-compliant media descriptions are certainly desirable. Essentially, MPEG-7 media descriptions are XML documents following media description schemes defined with a variant of XML Schema. Thus, it is reasonable to investigate current database solutions for XML documents regarding their suitability for the management of these descriptions. In this paper, we motivate and present critical requirements for the management of MPEG-7 media descriptions and the resulting consequences for XML database solutions. Along these requirements, we discuss current state-of-the-art database solutions for XML documents. The analysis and comparison unveil the limitations of current database solutions with respect to the management of MPEG-7 media descriptions and point the way to the need for a new generation of XML database solutions.

A cross-media adaptation strategy for multimedia presentations

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.

Using an object-oriented approach to model multimedia data

Abstract Special requirements are identified that arise in the handling of multimedia data. Individual objects, e.g. documents, should be extendable beyond their types. Data dispersed over several databases must be integrated and handled uniformly. A clear distinction is to be drawn between the (internal) modelling and the (external) presentation of multimedia objects. Data model constructs should be provided to define various semantic relationships, such as roles, copies, and versions. A reference architecture for multimedia databases is introduced and the requirements are associated with the different components of this architecture. It is shown how object-oriented data models can be used and extended to meet the requirements set out above. In particular, the metaclass concept is proposed to provide at the meta level those features of the data model that are needed to handle multimedia applications.

Z/sub Y/X-a multimedia document model for reuse and adaptation of multimedia content

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 users local context and needs. The approach significantly impacts and supports the authoring process in terms of methodology and economic aspects.

ebXML: status, research issues, and obstacles

Technologies and approaches in the field of electronic commerce are not mature enough in order to allow for their broad successful commercial application. Neither existing, successful approaches that are very much restricted to large companies, specific branches, and business domains, nor approaches just merging new technologies like Internet, WWW, and XML allow for scaling up electronic commerce by means of arbitrarily high numbers of partners. All these approaches lack substantial reflection and integration of business semantics as the basis of any electronic commerce partnership. ebXML is a world-wide initiative that tries to address the drawbacks of existing standards and approaches and has the potential to successfully deliver solutions to these problems. We address the status of ebXML and identify open research issues to be solved in order to meet some of the obstacles on the way to a commercial application of ebXML.

ZYX - A Semantic Model for Multimedia Documents and Presentations

Existing languages, formats, and multimedia document models such as HTML, MHEG, SMIL, HyTime, SGML, and XML, do not provide the appropriate modeling primitives needed to provide adequate support for reusability, interaction, adaptation, and presentation-neutral description of the structure and content of multimedia documents as required in the Cardio-OP project. Since each of these models lacks some significant concepts and does not meet all of the requirements, we propose a new approach for the semantic modeling of multimedia content, the ZYX model, which we implemented on the basis of an object-relational database system. The approach taken allows for fine-grained representation and retrieval of structures and layout of multimedia material, for flexible on-the-fly composition of multimedia fragments in order to create individualized multimedia documents, and for the realization of adaptation and personalization of multimedia presentations depending on the user environment specified by means of user profiles.

History merging as a mechanism for concurrency control in cooperative environments

Cooperative applications need proper transactional support for coordinating joint activities, sharing of data, and semantically correct exchange of information of collaborating users. Conventional transaction models based on the ACID properties do not meet the typical requirements of cooperative applications. The CoACT model (M. Rusinkiewicz et al., 1995) is designed for supporting cooperative work in multi user environments. CoACT includes a novel algorithm implementing the semantically correct exchange of information among concurrent activities of cooperating users by means of merging histories of user activities. This technique of merging activity histories is applicable in various fields beyond CSCW systems, e.g., in the area of mobile computing to manage disconnected operation.

Object-Oriented Modeling for Hypermedia Systems using the VODAK Modelling Language (VML)

More and more documents become available in electronic form, e.g., in the publishing sector, product design and specification, documentation, medical records, etc. Real applications in industry have a serious problem of handling masses of documents. Therefore, there is a growing demand of database support in the areas of document modelling, in particular hypermedia document modelling, i.e. documents containing multimedia data. As documents represent intrinsically complex structured data object-oriented database management (OODBMS) technology with its ability to handle such kind of information offers itself as a very promising way to tackle this problem as opposed to conventional database technology which was designed to handle simple structured data. OODBMS technology, although fairly developed today, needs to be extended and adapted to meet the specific requirements of hypermedia document modelling. Within the VODAK project at GMD-IPSI we developed an open OODBMS. Its data model VML can be tailored to the needs of particular applications. In this paper we first present the key principles and main features of the open object-oriented data model VML which can be extended at the meta level. This includes utilizing the concept of metaclasses. By this, system administrators may tailor the kernel data model to the requirements of specific applications and introduce, for example, additional types of links as they can be found in hypertext models at the data-model level. Second we illustrate how this open object-oriented data model can be tailored to the needs of modelling hypermedia documents as they are used in the framework of, e.g., collaborative authoring environments. We incrementally develop a model for hypermedia documents, discuss the advantages and disadvantages as well as the various alternatives.

A Comparison of Multimedia Document Models Concerning Advanced Requirements

Existing multimedia document models like HTML, MHEG, SMIL, and HyTime lack appropriate modeling primitives that meet speci�c requirements given by advanced multimedia information system applications. In traditional multimedia applications, multimedia document models just had to cope with the modeling of the temporal, spatial, and interactive course of a multimedia presentation. However, we seriously question whether existing models fit the needs of next generation multimedia applications that bring up requirements like reusability of multimedia content in different presentations and contexts, and adaptation to user preferences. In this paper, we motivate and present new requirements stemming from advanced multimedia applications and the resulting consequences for multimedia document models. Along these requirements, we discuss HTML, HyTime, MHEG, SMIL, and ZYX, a new model that has been developed with special focus on reusability and adaptation. The analysis and comparison of the models show the limitations of existing models, point the way to the need for new exible multimedia document models, and throw light on the many implications on authoring systems, multimedia content management, and presentation.