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Tutorial given at the Second Indo-American Conference on Knowledge Graphs and Semantic Web: KGSWC-2021 https://kgswc.org/winter-school-virtual/

In this paper we describe the architecture of a Research Management System based on Semantic technologies. The system is composed from two main modules: ontological infrastructure and research management system which are communicated through an RDF triple store that integrates all the information. The data model is defined in terms of Shape Expressions which are synchronized with Java entities that define the data model. The shapes also act as core layer that can be used to describe the main entities that will be employed and to validate their ontological definitions with test data. In this way, we propose a testdriven development approach for ontological engineering that improves the quality of both the ontologies defined and the data. The semantic architecture is based on a reactive approach which combines both a clean architecture and a stream-based pattern. This paper describes the architecture of the system and the main quality attributes and design decisions that have been taken into account.

Wikidata, the free knowledge base in the Wikimedia movement, is used by various Wikimedia projects and third parties to provide machine-readable information and data. Its data quality is managed and monitored by its community using several quality control mechanisms, recently including formal schemas in the Shape Expressions language. However, larger schemas can be tedious to write, making automatic inference of schemas from a set of exemplary Items an attractive prospect. This thesis investigates this option by updating and adapting the RDF2Graph program to infer schemas from a set of Wikidata Items, and providing a web-based tool which makes this process available to the Wikidata community. Though the resulting schemas are usually not fit for direct validation, they can still be useful as a form of describing the layout of an area of Wikidata’s data model, a way to notice potential issues in the source data, or a basis for a manually curated schema., master-thesis-final.tar.gz is a tarball of the thesis' source code, from which it should be possible to build the thesis by running `make`; master-thesis-Lucas-Werkmeister.pdf is the PDF built directly by PDFLaTeX; and master-thesis-Lucas-Werkmeister-signed.pdf is a signed version of master-thesis-Lucas-Werkmeister.pdf, signed with the PortableSigner software using the author's certificate from the KIT CA.

International audience; ShEx (Shape Expressions) is a language for expressing constraints on RDF graphs. In this work we optimize the evaluation of conjunctive SPARQL queries, on RDF graphs, by taking advantage of ShEx constraints. Our optimization is based on computing and assigning ranks to query triple patterns , dictating their order of execution. We first define a set of well formed ShEx schemas, that possess interesting characteristics for SPARQL query optimization. We then define our optimization method by exploiting information extracted from a ShEx schema. We finally report on evaluation results performed showing the advantages of applying our optimization on the top of an existing state-of-the-art query evaluation system.

Slides for a presentation to the Force2017 Software Citation Implementation Working Group describing software and file format data in Wikidata and data validation using ShEx.

International audience; ShEx (Shape Expressions) is a language for expressing constraints on RDF graphs. In this work, we optimise the evaluation of conjunctive SPARQL queries, on RDF graphs, by taking advantage of ShEx constraints. Our optimisation is based on computing and assigning ranks to query triple patterns, dictating their order of execution. We first define a set of well-formed ShEx schemas, that possess interesting characteristics for SPARQL query optimisation. We then define our optimisation method by exploiting information extracted from a ShEx schema. We finally report on evaluation results performed showing the advantages of applying our optimisation on the top of an existing state-of-the-art query evaluation system.