“…These approaches use several techniques for retrieving the best match results, by exploiting Information Retrieval (IR) techniques [18,19], and/or by adapting existing IR systems, like Elasticsearch, to the needs of RDF, for example, see [1,2,20] and others. As regards (c), there are several interactive information access systems, including browsing systems, such as [3,4,21] and also systems that can aid users that are not familiar with query languages to access the RDF knowledge base, for example, faceted search [6,7,13], interactive analytics services [22,23] and also systems for assisting the query building process, such as the system A-Qub [8]. Finally, regarding (d) Natural Language interface systems [24], where the input and output is given in natural language, and it returns short and precise answers, that is, through conversational access and Question Answering systems [25][26][27][28].…”