Antoine Isaac

An empirical study of instance-based ontology matching

Instance-based ontology mapping is a promising family of solutions to a class of ontology alignment problems. It crucially depends on measuring the similarity between sets of annotated instances. In this paper we study how the choice of co-occurrence measures affects the performance of instance-based mapping. To this end, we have implemented a number of different statistical co-occurrence measures. We have prepared an extensive test case using vocabularies of thousands of terms, millions of instances, and hundreds of thousands of co-annotated items. We have obtained a human Gold Standard judgement for part of the mapping-space. We then study how the different co-occurrence measures and a number of algorithmic variations perform on our benchmark dataset as compared against the Gold Standard. Our systematic study shows excellent results of instance-based matching in general, where the more simple measures often outperform more sophisticated statistical co-occurrence measures.

Europeana Linked Open Data --data.europeana.eu

Europeana is a single access point to millions of books, paintings, films, museum objects and archival records that have been digitized throughout Europe. The data.europeana.eu Linked Open Data pilot dataset contains open metadata on approximately 2.4 million texts, images, videos and sounds gathered by Europeana. All metadata are released under Creative Commons CC0 and therefore dedicated to the public domain. The metadata follow the Europeana Data Model and clients can access data either by dereferencing URIs, downloading data dumps, or executing SPARQL queries against the dataset. They can also follow the links to external linked data sources, such as the Swedish cultural heritage aggregator SOCH, GeoNames, the GEMET thesaurus, or DBPedia.

LCSH, SKOS and linked data

A technique for converting Library of Congress Subject Headings MARCXML to Simple Knowledge Organization System (SKOS) RDF is described. Strengths of the SKOS vocabulary are highlighted, as well as possible points for extension, and the integration of other semantic web vocabularies such as Dublin Core. An application for making the vocabulary available as linked-data on the Web is also described.

Ontology paper: Key choices in the design of Simple Knowledge Organization System (SKOS)

A technique for converting Library of Congress Subject Headings MARCXML to Simple Knowledge Organization System (SKOS) RDF is described. Strengths of the SKOS vocabulary are highlighted, as well as possible points for extension, and the integration of other semantic web vocabularies such as Dublin Core. An application for making the vocabulary available as linked-data on the Web is also described.

Semantic web techniques for multiple views on heterogeneous collections: a case study

Integrated digital access to multiple collections is a prominent issue for many Cultural Heritage institutions. The metadata describing diverse collections must be interoperable, which requires aligning the controlled vocabularies that are used to annotate objects from these collections. In this paper, we present an experiment where we match the vocabularies of two collections by applying the Knowledge Representation techniques established in recent Semantic Web research. We discuss the steps that are required for such matching, namely formalising the initial resources using Semantic Web languages, and running ontology mapping tools on the resulting representations. In addition, we present a prototype that enables the user to browse the two collections using the obtained alignment while still providing her with the original vocabulary structures.

Finding quality issues in SKOS vocabularies

The Simple Knowledge Organization System (SKOS) is a standard model for controlled vocabularies on the Web. However, SKOS vocabularies often differ in terms of quality, which reduces their applicability across system boundaries. Here we investigate how we can support taxonomists in improving SKOS vocabularies by pointing out quality issues that go beyond the integrity constraints defined in the SKOS specification. We identified potential quantifiable quality issues and formalized them into computable quality checking functions that can find affected resources in a given SKOS vocabulary. We implemented these functions in the qSKOS quality assessment tool, analyzed 15 existing vocabularies, and found possible quality issues in all of them.

Matching multi-lingual subject vocabularies

Most libraries and other cultural heritage institutions use controlled knowledge organisation systems, such as thesauri, to describe their collections. Unfortunately, as most of these institutions use different such systems, unified access to heterogeneous collections is difficult. Things are even worse in an international context when concepts have labels in different languages. In order to overcome the multilingual interoperability problem between European Libraries, extensive work has been done to manually map concepts from different knowledge organisation systems, which is a tedious and expensive process. Within the TELplus project, we developed and evaluated methods to automatically discover these mappings, using different ontology matching techniques. In experiments on major French, English and German subject heading lists Rameau, LCSH and SWD, we show that we can automatically produce mappings of surprisingly good quality, even when using relatively naive translation and matching methods.

Evaluating Thesaurus Alignments for Semantic Interoperability in the Library Domain

Thesaurus alignments play an important role in realizing efficient access to heterogeneous cultural-heritage data. Current technology, however, provides only limited value for such access because it fails to bridge the gap between theoretical study and practical application requirements. This article explores common real-world library problems and identifies solutions that focus on the application-embedded study, development, and evaluation of matching technology.

Integrated access to cultural heritage resources through representation and alignment of controlled vocabularies

Purpose – To show how semantic web techniques can help address semantic interoperability issues in the broad cultural heritage domain, allowing users an integrated and seamless access to heterogeneous collections.Design/methodology/approach – This paper presents the heterogeneity problems to be solved. It introduces semantic web techniques that can help in solving them, focusing on the representation of controlled vocabularies and their semantic alignment. It gives pointers to some previous projects and experiments that have tried to address the problems discussed.Findings – Semantic web research provides practical technical and methodological approaches to tackle the different issues. Two contributions of interest are the simple knowledge organisation system model and automatic vocabulary alignment methods and tools. These contributions were demonstrated to be usable for enabling semantic search and navigation across collections.Research limitations/implications – The research aims at designing different...

Two variations on ontology alignment evaluation: methodological issues

Evaluation of ontology alignments is in practice done in two ways: (1) assessing individual correspondences and (2) comparing the alignment to a reference alignment. However, this type of evaluation does not guarantee that an application which uses the alignment will perform well. In this paper, we contribute to the current ontology alignment evaluation practices by proposing two alternative evaluation methods that take into account some characteristics of a usage scenario without doing a full-fledged end-to-end evaluation. We compare different evaluation approaches in three case studies, focussing on methodological issues. Each case study considers an alignment between a different pair of ontologies, ranging from rich and well-structured to small and poorly structured. This enables us to conclude on the use of different evaluation approaches in different settings.