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Visualizations can improve the modeling process as they are specifically designed for human information processing, possibly leading to more accurate constraints, and in turn higher quality knowledge graphs. However, it is currently unknown how such visualizations support users when viewing RDF constraints as no scientific evidence for the visualizations\u2019 effectiveness is provided. Furthermore, some of the existing tools are likely suboptimal, as they lack support for edit\u00a0operations or common constraints types. To establish a\u00a0baseline, we have defined visual notations to represent RDF constraints and implemented them in UnSHACLed, a\u00a0tool that is independent of a\u00a0concrete RDF constraint language. In this paper, we (i)\u00a0present two visual notations that support all SHACL core constraints, built upon the commonly used visualizations VOWL and UML, (ii)\u00a0analyze both notations based on cognitive effective design principles, (iii)\u00a0perform a comparative user study between both visual notations, and (iv)\u00a0present our open source tool UnSHACLed incorporating our efforts. Users were presented RDF constraints in both visual notations and had to answer questions based on visualization task taxonomies. Although no statistical significant difference in mean error rates was observed, all study participants preferred ShapeVOWL in a self assessment to answer RDF constraint-related questions. Furthermore, ShapeVOWL adheres to more cognitive effective design principles according to our performed comparison. Study participants argued that the increased visual features of ShapeVOWL made it easier to spot constraints, but a list of constraints\u00a0\u2013 as in ShapeUML\u00a0\u2013 is easier to read. However, also that more deviations from the strict UML specification and introduction of more visual features can improve ShapeUML. From these findings we conclude that ShapeVOWL has a higher potential to represent RDF constraints more effective compared to ShapeUML. But also that the clear and efficient text encoding of ShapeUML can be improved with visual features. A\u00a0one-size-fits-all approach to RDF constraint visualization and editing will be insufficient. Therefore, to support different audiences and use cases, user interfaces of RDF constraint editors need to support different visual notations.<\/jats:p>","DOI":"10.3233\/sw-210450","type":"journal-article","created":{"date-parts":[[2021,11,23]],"date-time":"2021-11-23T18:40:30Z","timestamp":1637692830000},"page":"757-792","source":"Crossref","is-referenced-by-count":2,"title":["Visual notations for viewing RDF constraints with UnSHACLed"],"prefix":"10.1177","volume":"13","author":[{"given":"Sven","family":"Lieber","sequence":"first","affiliation":[{"name":"IDLab, Department of Electronics and Information Systems, Ghent University\u2013Imec, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ben","family":"De\u00a0Meester","sequence":"additional","affiliation":[{"name":"IDLab, Department of Electronics and Information Systems, Ghent University\u2013Imec, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Pieter","family":"Heyvaert","sequence":"additional","affiliation":[{"name":"IDLab, Department of Electronics and Information Systems, Ghent University\u2013Imec, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Femke","family":"Br\u00fcckmann","sequence":"additional","affiliation":[{"name":"IDLab, Department of Electronics and Information Systems, Ghent University\u2013Imec, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ruben","family":"Wambacq","sequence":"additional","affiliation":[{"name":"IDLab, Department of Electronics and Information Systems, Ghent University\u2013Imec, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Erik","family":"Mannens","sequence":"additional","affiliation":[{"name":"IDLab, Department of Electronics and Information Systems, Ghent University\u2013Imec, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ruben","family":"Verborgh","sequence":"additional","affiliation":[{"name":"IDLab, Department of Electronics and Information Systems, Ghent University\u2013Imec, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Anastasia","family":"Dimou","sequence":"additional","affiliation":[{"name":"IDLab, Department of Electronics and Information Systems, Ghent University\u2013Imec, Belgium"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"179","reference":[{"key":"10.3233\/SW-210450_ref1","doi-asserted-by":"publisher","DOI":"10.1007\/978-3-319-76348-4_84"},{"key":"10.3233\/SW-210450_ref2","doi-asserted-by":"publisher","DOI":"10.1109\/INFVIS.2005.1532136"},{"key":"10.3233\/SW-210450_ref3","doi-asserted-by":"publisher","DOI":"10.1007\/978-3-319-65551-2_10"},{"key":"10.3233\/SW-210450_ref4","unstructured":"J.\u00a0Bertin, Semiology of Graphics: Diagrams Networks, Maps, Technical Report, University of Wisconsin Press, 1983."},{"key":"10.3233\/SW-210450_ref6","unstructured":"I.\u00a0Boneva, J.\u00a0Dusart, D.\u00a0Fern\u00e1ndez Alvarez and J.E.L.\u00a0Gayo, Shape designer for ShEx and SHACL constraints, in: Proceedings of the ISWC 2019 Satellite Tracks (Poster & Demonstrations, Industry, and Outrageous Ideas), Vol.\u00a02456, CEUR-WS.org, 2019, pp.\u00a0269\u2013272, https:\/\/hal.archives-ouvertes.fr\/hal-02268667."},{"key":"10.3233\/SW-210450_ref7","unstructured":"T.\u00a0Bosch, A.\u00a0Nolle, E.\u00a0Acar and K.\u00a0Eckert, RDF Validation Requirements\u00a0\u2013 Evaluation and Logical Underpinning, 2015, http:\/\/arxiv.org\/abs\/1501.03933."},{"issue":"3","key":"10.3233\/SW-210450_ref8","doi-asserted-by":"publisher","first-page":"365","DOI":"10.1007\/s13218-020-00657-8","article-title":"crowd: A visual tool for involving stakeholders into ontology engineering tasks, KI","volume":"34","author":"Braun","year":"2020","journal-title":"K\u00fcnstliche Intelligenz"},{"issue":"12","key":"10.3233\/SW-210450_ref9","doi-asserted-by":"publisher","first-page":"2376","DOI":"10.1109\/TVCG.2013.124","article-title":"A multi-level typology of abstract visualization tasks","volume":"19","author":"Brehmer","year":"2013","journal-title":"IEEE Transactions on Visualization and Computer Graphics"},{"key":"10.3233\/SW-210450_ref10","doi-asserted-by":"publisher","DOI":"10.1007\/978-3-030-49461-2_29"},{"key":"10.3233\/SW-210450_ref11","unstructured":"S.\u00a0Cranefield and M.\u00a0Purvis, UML as an Ontology Modelling Language, in: Intelligent Information Integration, 1999."},{"key":"10.3233\/SW-210450_ref12","unstructured":"J.W.\u00a0Creswell, Research Design: Qualitative, Quantitative, and Mixed Methods Approaches, 3rd edn, Sage Publications Ltd., 2008. 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