François Scharffe

The Alignment API 4.0

Alignments represent correspondences between entities of two ontologies. They are produced from the ontologies by ontology matchers. In order for matchers to exchange alignments and for applications to manipulate matchers and alignments, a minimal agreement is necessary. The Alignment API provides abstractions for the notions of network of ontologies, alignments and correspondences as well as building blocks for manipulating them such as matchers, evaluators, renderers and parsers. We recall the building blocks of this API and present here the version 4 of the Alignment API through some of its new features: ontology proxys, the expressive alignment language EDOAL and evaluation primitives.

Data Linking for the Semantic Web

By specifying that published datasets must link to other existing datasets, the 4th linked data principle ensures a Web of data and not just a set of unconnected data islands. The authors propose in this paper the term data linking to name the problem of finding equivalent resources on the Web of linked data. In order to perform data linking, many techniques were developed, finding their roots in statistics, database, natural language processing and graph theory. The authors begin this paper by providing background information and terminological clarifications related to data linking. Then a comprehensive survey over the various techniques available for data linking is provided. These techniques are classified along the three criteria of granularity, type of evidence, and source of the evidence. Finally, the authors survey eleven recent tools performing data linking and we classify them according to the surveyed techniques.

Correspondence Patterns for Ontology Alignment

We introduce in this paper correspondence patternsas templates to model ontology alignments. Correspondence patterns capture regularities recurring when aligning ontologies. They come in complement of ontology matching algorithms and graphical mapping tools, and facilitate the task of the engineer building the alignment between a pair of ontologies. We develop an ontology mediation framework based on three ontology correspondence abstraction levels. We particularly detail the most abstract level: correspondence patterns.

Processing Ontology Alignments with SPARQL

Solving problems raised by heterogeneous ontologies can be achieved by matching the ontologies and processing the resulting alignments. This is typical of data mediation in which the data must be translated from one knowledge source to another. We propose to solve the data translation problem, i.e. the processing part, using the SPARQL query language. Indeed, such a language is particularly adequate for extracting data from one ontology and, through its CONSTRUCT statement, for generating new data. We present examples of such transformations, but we also present a set of example correspondences illustrating the needs for particular representation constructs, such as aggregates, value generating built-in functions and paths, which are missing from SPARQL. Hence, we advocate the use of two SPARQL extensions providing these missing features.

Ontology alignment design patterns

Interoperability between heterogeneous ontological descriptions can be performed through ontology mediation techniques. At the heart of ontology mediation lies the alignment: a specification of correspondences between ontology entities. Ontology matching can bring some automation but are limited to finding simple correspondences. Design patterns have proven themselves useful to capture experience in design problems. In this article, we introduce ontology alignment patterns as reusable templates of recurring correspondences. Based on a detailed analysis of frequent ontology mismatches, we develop a library of common patterns. Ontology alignment patterns can be used to refine correspondences, either by the alignment designer or via pattern detection algorithms. We distinguish three levels of abstraction for ontology alignment representation, going from executable transformation rules, to concrete correspondences between two ontologies, to ontology alignment patterns at the third level. We express patterns using an ontology alignment representation language, making them ready to use in practical mediation tasks. We extract mismatches from vocabularies associated with data sets published as linked open data, and we evaluate the ability of correspondence patterns to provide proper alignments for these mismatches. Finally, we describe an application of ontology alignment patterns for an ontology transformation service.

Keys and pseudo-keys detection for web datasets cleansing and interlinking

This paper introduces a method for analyzing web datasets based on key dependencies. The classical notion of a key in relational databases is adapted to RDF datasets. In order to better deal with web data of variable quality, the definition of a pseudo-key is presented. An RDF vocabulary for representing keys is also provided. An algorithm to discover keys and pseudo-keys is described. Experimental results show that even for a big dataset such as DBpedia, the runtime of the algorithm is still reasonable. Two applications are further discussed: (i) detection of errors in RDF datasets, and (ii) datasets interlinking.

Towards design patterns for ontology alignment

Aligning ontologies is a crucial and tedious task. Matching algorithms and tools provide support to facilitate the task of the user in defining correspondences between ontologies entities. However, automatic matching is actually limited to the detection of simple one to one correspondences to be further refined by the user. We propose in this paper the use of correspondence patterns as a tool to assist the design of ontology alignments. Based on existing research on patterns in the fields of software and ontology engineering, we propose a pattern template as an helper to develop a correspondence patterns library. We give ways towards the representation of patterns using an appropriate correspondence representation formalism: the Alignment Ontology.

Publishing and linking transport data on the web: extended version

Without Linked Data, transport data is limited to applications exclusively around transport. In this paper, we present a workflow for publishing and linking transport data on the Web. So we will be able to develop transport applications and to add other features which will be created from other datasets. This will be possible because transport data will be linked to these datasets. We apply this workflow to two datasets: NEPTUNE, a French standard describing a transport line, and Passim, a directory containing relevant information on transport services, in every French city.

Defining Key Semantics for the RDF Datasets: Experiments and Evaluations

Many techniques were recently proposed to automate the linkage of RDF datasets. Predicate selection is the step of the linkage process that consists in selecting the smallest set of relevant predicates needed to enable instance comparison. We call keys this set of predicates that is analogous to the notion of keys in relational databases. We explain formally the different assumptions behind two existing key semantics. We then evaluate experimentally the keys by studying how discovered keys could help dataset interlinking or cleaning. We discuss the experimental results and show that the two different semantics lead to comparable results on the studied datasets.

Negotiating the web science curriculum through shared educational artefacts

The far-reaching impact of the Web on society is widely recognised. The interdisciplinary study of this impact has crystallised in the field of study known as Web Science. However, defining an agreed, shared understanding of what constitutes web science requires complex negotiation and translations of understandings across component disciplines, national cultures and educational traditions. Some individual institutions have already established particular curricula, and discussions in the Web Science Curriculum Workshop series have marked the territory to some extent. This paper reports on a process being adopted across a consortium of partners to systematically create a shared understanding of what constitutes web science. It records and critiques the processes instantiated to agree a common curriculum, and presents a framework for future discussion and development.