Michiel Hildebrand

/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.

Semantic annotation and search of cultural-heritage collections: The MultimediaN E-Culture demonstrator

In this article we describe a Semantic Web application for semantic annotation and search in large virtual collections of cultural-heritage objects, indexed with multiple vocabularies. During the annotation phase we harvest, enrich and align collection metadata and vocabularies. The semantic-search facilities support keyword-based queries of the graph (currently 20M triples), resulting in semantically grouped result clusters, all representing potential semantic matches of the original query. We show two sample search scenarios. The annotation and search software is open source and is already being used by third parties. All software is based on established Web standards, in particular HTML/XML, CSS, RDF/OWL, SPARQL and JavaScript.

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.

Supporting subject matter annotation using heterogeneous thesauri

We performed a user experiment in which museum professionals used vocabularies from the Web for annotating the subject matter of museum objects. In this paper, we study the requirements on the underlying RDF dataset, search algorithms and user interface design in a real world setting. We identify the advantages of reusing vocabularies from the Web and discuss how and to what extent the disadvantages can be overcome. The study is performed at the Print Room of the Rijksmuseum Amsterdam, where currently a large collection of prints, photographs and drawings is being catalogued. We report on the analysis of the current practice of professional cataloguers, the iterative design of an annotation tool and a qualitative evaluation of this tool with a user experiment in a realistic annotation environment. We discuss our findings in terms of their impact on the RDF data, the semantic search functionality and the user interface.

Organizing Suggestions in Autocompletion Interfaces

We describe two user studies that investigate organization strategies of autocompletion in a known-item search task: searching for terms taken from a thesaurus. In Study 1, we explored ways of grouping term suggestions from two different thesauri (TGN and WordNet) and found that different thesauri may require different organization strategies. Users found Group organization more appropriate for location names from TGN, while Alphabetical works better for object names from WordNet. In Study 2, we compared three different organization strategies (Alphabetical , Group and Composite ) for location name search tasks. The results indicate that for TGN autocompletion interfaces help improve the quality of keywords, Group and Composite organization help users search faster, and is perceived easier to understand and to use than Alphabetical .

ClioPatria: A SWI-Prolog infrastructure for the Semantic Web

ClioPatria is a comprehensive semantic web development framework based on SWI-Prolog. SWI-Prolog provides an efficient C-based main-memory RDF store that is designed to cooperate naturally and efficiently with Prolog, realizing a flexible RDF-based environment for rule based programming. ClioPatria extends this core with a SPARQL and LOD server, an extensible web frontend to manage the server, browse the data, query the data using SPARQL and Prolog and a Git-based plugin manager. The ability to query RDF using Prolog provides query composition and smooth integration with application logic. ClioPatria is primarily positioned as a prototyping platform for exploring novel ways of reasoning with RDF data. It has been used in several research projects in order to perform tasks such as data integration and enrichment and semantic search.

Augmenting TV Newscasts via Entity Expansion

We present an approach that leverages on the knowledge present on the Web for identifying and enriching relevant items inside a News video and displaying them in a timely and user friendly fashion. This second screen prototype (i) collects and offers information about persons, locations, organizations and concepts occurring in the newscast, and (ii) combines them for enriching the underlying story along five main dimensions: expert’s opinions, timeline, in depth, in other sources, and geo-localized comments from other viewers. Starting from preliminary insights coming from the named entities spotted on the subtitles, we expand this initial context to a broader event representation by relying in the knowledge of other Web documents talking about the same fact. An online demo of the proposed solution is available at http://www.linkedtv.project.cwi.nl/news/.

Interactive Exploration of Heterogeneous Cultural Heritage Collections

In this research we investigate to what extent explicit semantics can be used to support end users with the exploration of a large heterogeneous collection. In particular we consider cultural heritage, a knowledge-rich domain in which collections are typically described by multiple thesauri. Many institutions have made or are making (parts of) their collections available online. The cultural heritage community has the ambition to make these isolated collections and thesauri interoperable and allow users to explore cultural heritage in a richer environment.

Exploring Audiovisual Archives Through Aligned Thesauri

As audiovisual archives are digitizing their collections and making these collections available online, the need arises to also establish connections between different collections and to allow for cross-collection search and browsing. Structured vocabularies, made available as Linked Data, can be used as connecting points by aligning thesauri from different institutions. In this paper, we present a case study where partial collections of two audiovisual archives are connected by aligning their thesauri. We report on the conversion of one of the thesauri to SKOS and on the subsequent application of an interactive alignment tool “CultuurLINK”. Finally, we introduce an cross-collection browser which uses the produced alignment to allow users to explore connections between the two collections.

Time-based tags for fiction movies: comparing experts to novices using a video labeling game

The cultural heritage sector has embraced social tagging as a way to increase both access to online content and to engage users with their digital collections. In this article, we build on two current lines of research. (a) We use Waisda?, an existing labeling game, to add time‐based annotations to content. (b) In this context, we investigate the role of experts in human‐based computation (nichesourcing). We report on a small‐scale experiment in which we applied Waisda? to content from film archives. We study the differences in the type of time‐based tags between experts and novices for film clips in a crowdsourcing setting. The findings show high similarity in the number and type of tags (mostly factual). In the less frequent tags, however, experts used more domain‐specific terms. We conclude that competitive games are not suited to elicit real expert‐level descriptions. We also confirm that providing guidelines, based on conceptual frameworks that are more suited to moving images in a time‐based fashion, could result in increasing the quality of the tags, thus allowing for creating more tag‐based innovative services for online audiovisual heritage.