Juma: an Editor that Uses a Block Metaphor to Facilitate the Creation and Editing of R2RML Mappings Ademar Crotti Junior, Christophe Debruyne, Declan O’Sullivan ADAPT Centre, Trinity College Dublin, Dublin 2, Ireland {crottija,debruync,declan.osullivan}@scss.tcd.ie Abstract. R2RML is the W3C standard mapping language used to define cus- tomized mappings from relational databases into RDF. One issue that hampers its adoption is the effort needed in the creation of such mappings, as they are stored as RDF documents. To address this problem, several tools that represent mappings as graphs have been proposed in the literature. In this paper, we de- scribe a visual representation based on a block metaphor for creating and edit- ing such mappings that is fully compliant with the R2RML specification. Pre- liminary findings from users using the tool indicate that the visual representa- tion was helpful in the creation of R2RML mappings with good usability re- sults. In future work, we intend to conduct more experiments focusing on dif- ferent types of users and to abstract the visual representation from the R2RML mapping language so that it supports the serialization of other uplift mapping languages. Keywords. R2RML; Visual Representation; Data Mapping. 1 Introduction A significant part of the Linked Data web is achieved by converting non-RDF re- sources into RDF. This conversion process is typically called uplift. For relational databases, one can rely on the W3C Recommendation R2RML 1 for creating mappings from relational databases into RDF datasets. Though useful, some problems with its adoption can be observed. Firstly, R2RML mappings are stored as RDF. We argue that writing any RDF graph by hand can be troublesome and prone to errors. Second- ly, the R2RML mapping language has a steep learning curve, where the creation of mappings is time consuming, and syntactically heavy in various cases [9]. Initiatives have emerged to address these problems and make the technology more accessible such as visual graph representations for engaging with mappings [6, 7] and others that will be discussed in Section 2. In this paper, we describe a visual representation for mappings called Juma. Our representation is based on the block (or jigsaw) metaphor that has become popular with visual programming languages – where it is called the block paradigm – such as Scratch 2 . This metaphor allows one to focus on the logic instead of the language’s 1 https://www.w3.org/TR/r2rml/ 2 https://scratch.mit.edu/, last accessed March 2017