Jacco van Ossenbruggen

/facet: a browser for heterogeneous semantic web repositories

Facet browsing has become popular as a user friendly interface to data repositories. The Semantic Web raises new challenges due to the heterogeneous character of the data. First, users should be able to select and navigate through facets of resources of any type and to make selections based on properties of other, semantically related, types. Second, where traditional facet browsers require manual configuration of the software, a semantic web browser should be able to handle any RDFS dataset without any additional configuration. Third, hierarchical data on the semantic web is not designed for browsing: complementary techniques, such as search, should be available to overcome this problem. We address these requirements in our browser, /facet. Additionally, the interface allows the inclusion of facet-specific display options that go beyond the hierarchical navigation that characterizes current facet browsing. /facet is a tool for Semantic Web developers as an instant interface to their complete dataset. The automatic facet configuration generated by the system can then be further refined to configure it as a tool for end users. The implementation is based on current Web standards and open source software. The new functionality is motivated using a scenario from the cultural heritage domain.

Towards second and third generation web-based multimedia

First generation Web-content encodes information in handwritten (HTML) Web pages. Second generation Web content generates HTML pages on demand, e.g. by filling in templates with content retrieved dynamically from a database or transformation of structured documents using style sheets (e.g. XSLT). Third generation Web pages will make use of rich markup (e.g. XML) along with metadata (e.g. RDF) schemes to make the content not only machine readable but also machine processable - a necessary pre-requisite to the emphSemantic Web. While text-based content on the Web is already rapidly approaching the third generation, multimedia content is still trying to catch up with second generation techniques. Multimedia document processing has a number of fundamentally different requirements from text which make it more difficult to incorporate within the document processing chain. In particular, multimedia transformation uses different document and presentation abstractions, its formatting rules cannot be based on text-flow, it requires feedback from the formatting back-end and is hard to describe in the functional style of current style languages. We state the requirements for second generation processing of multimedia and describe how these have been incorporated in our prototype multimedia document transformation environment, emphCuypers. The system overcomes a number of the restrictions of the text-flow based tool sets by integrating a number of conceptually distinct processing steps in a single runtime execution environment. We describe the need for these different processing steps and describe them in turn (semantic structure, communicative device, qualitative constraints, quantitative constraints, final form presentation), and illustrate our approach by means of an example. We conclude by discussing the models and techniques required for the creation of third generation multimedia content.

MultimediaN e-culture demonstrator

The main objective of the MultimediaN E-Culture project is to demonstrate how novel semantic-web and presentation technologies can be deployed to provide better indexing and search support within large virtual collections of cultural-heritage resources. The architecture is fully based on open web standards, in particular XML, SVG, RDF/OWL and SPARQL. One basic hypothesis underlying this work is that the use of explicit background knowledge in the form of ontologies/vocabularies/thesauri is in particular useful in information retrieval in knowledge-rich domains.

Towards ontology-driven discourse: from semantic graphs to multimedia presentations

Traditionally, research in applying Semantic Web technology to multimedia information systems has focused on using annotations and ontologies to improve the retrieval process. This paper concentrates on improving the presentation of the retrieval results. First, our approach uses ontological domain knowledge to select and organize the content relevant to the topic the user is interested in. Domain ontologies are valuable in the presentation generation process, because effective presentations are those that succeed in conveying the relevant domain semantics to the user. Explicit discourse and narrative knowledge allows selection of appropriate presentation genres and creation of narrative structures, which are used for conveying these domain relations. In addition, knowledge of graphic design and media characteristics is essential to transform abstract presentation structures in real multimedia presentations. Design knowledge determines how the semantics and presentation structure are expressed in the multimedia presentation. In traditional Web environments, this type of design knowledge remains implicit, hidden in style sheets and other document transformation code. Our second use of Semantic Web technology is to model design knowledge explicitly, and to let it drive the transformations needed to turn annotated media items into structured presentations.

Generating presentation constraints from rhetorical structure

Hypermedia structured in terms of the higher-level intent of its author can be adapted to a wider variety of final presentations. Many multimedia systems encode such high-level intent as constraints on either time, spatial layout or navigation. Once specified, these constraints are translated into specific presentations whose timelines, screen displays and navigational structure satisfy these constraints. This ensures that the desired spatial, temporal and navigation properties are maintained no matter how the presentation is adapted to varying circumstances. Rhetorical structure defines author intent at a still higher level. Authoring at this level requires that rhetorics can be translated to final presentations that properly reflect them. This paper explores how rhetorical structure can be translated into constraints, which are then translated into final presentations. This enables authoring in terms of rhetorics and provides the assurance that the rhetorics will remain properly conveyed in all presentation adaptation.

Making RDF presentable: integrated global and local semantic Web browsing

This paper discusses generating document structure from annotated media repositories in a domain-independent manner. This approaches the vision of a universal RDF browser. We start by applying the search-and-browse paradigm established for the WWW to RDF presentation. Furthermore, this paper adds to this paradigm the clustering-based derivation of document structure from search returns, providing simple but domain-independent hypermedia generation from RDF stores. While such generated presentations hardly meet the standards of those written by humans, they provide quick access to media repositories when the required document has not yet been written. The resulting system allows a user to specify a topic for which it generates a hypermedia document providing guided navigation through virtually any RDF repository. The impact for content providers is that as soon as one adds new media items and their annotations to a repository, they become immediately available for automatic integration into subsequently requested presentations.

Structural distinctions between hypermedia storage and presentation

In order to facilitate adaptability of hypermedia documents a distinction is often made between the underlying conceptual structure of a document and the structure of its presentation. This distinction enables greater variety in how a presentation can be adapted to best convey these underlying concepts in a given situation. What is often confusing for those applying this distinction is that although both levels of structure often share similar components: transformation form the storage of a document to its presentation sometimes occurs directly between these similar components and sometimes does not. These similarities typically fall in the categories of space, time and relationships between document portions. This paper identifies some primary similarities between the structure of hypermedia storage and presentation. It also explores how the transformation from storage to presentation often does not follow these similarities. This discussion is illustrated with the Fiets hypermedia application, which addresses the issues of storage, presentation and transformation using public domain formats and tools. The intention is to help authors who separate storage from presentation to better understand this distinction.

Towards a multimedia formatting vocabulary

Time-based, media-centric Web presentations can be described declaratively in the XML world through the development of languages such as SMIL. It is difficult, however, to fully integrate them in a complete document transformation processing chain. In order to achieve the desired processing of data-driven, time-based, media-centric presentations, the text-flow based formatting vocabularies used by style languages such as XSL, CSS and DSSSL need to be extended. The paper presents a selection of use cases which are used to derive a list of requirements for a multimedia style and transformation formatting vocabulary. The boundaries of applicability of existing text-based formatting models for media-centric transformations are analyzed. The paper then discusses the advantages and disadvantages of a fully-fledged time-based multimedia formatting model. Finally, the discussion is illustrated by describing the key properties of the example multimedia formatting vocabulary currently implemented in the back-end of our Cuypers multimedia transformation engine.

Digital hermeneutics: Agora and the online understanding of cultural heritage

Cultural heritage institutions are currently rethinking access to their collections to allow the public to interpret and contribute to their collections. In this work, we present the Agora project, an interdisciplinary project in which Web technology and theory of interpretation meet. This we call digital hermeneutics. The Agora project facilitates the understanding of historical events and improves the access to integrated online history collections. In this contribution, we focus on defining and modeling prototypical object-event and event-event relationships that support the interpretation of objects in cultural heritage collections. We present a use case in which we model historical events as well as relations between objects and events for a set of paintings from the Rijksmuseum Amsterdam collection. Our use case shows how Web technology and theory of interpretation meet in the present, and what technological hurdles still need to be taken to fully support digital hermeneutics.

A framework for generating adaptable hypermedia documents

Being able to author a hypermedia document once for presentation under a wide variety of potential circumstances requires that it be stored in a manner that is adaptable to these circumstances. Since the nature of these circumstances is not always known at authoring time, specifying how a document adapts to them must be a process that can be performed separately from its original authoring. These distinctions include the porting of the document to different platforms and formats and the adapting of the document’s presentation to suit the needs of the user and of the current state of the presentation environment. In this paper we discuss extensions to our CMIF hypermedia authoring and presentation environment that provide adaptability through this distinction between authoring and presentation specification. This extension includes the use of HyTime for document representation and of DSSSL for presentation specification. We also discuss the Berlage architecture, our extension to HyTime that specifies the encoding of certain hypermedia concepts useful for presentation specification.