Based on the spreadsheet (Additional file 2) that resulted from the literature review, an RDF schema was developed and annotated using standard metadata vocabularies and specialized ontologies (Figure ). Table shows the ontologies used in developing the RDF along with their prefixes. The transformation from the spreadsheet to RDF was performed using the RDF Mapping Language (RML). RML is a scalable, general mapping language designed to map heterogeneous data structures onto RDF models . The process starts with creating a text document that contains rules on how each element in the spreadsheet can be mapped to a corresponding semantic expression. That is done by defining a subject map specifying the IRI structure for the subject and a set of predicate-object pairs to create the triples semantifying each cell value in the spreadsheet. The mapping document can be created using either RML rules directly or by using YARRRML as an intermediate representation which is then converted to RML using the YARRRML Parser . YARRRML is a human-readable text-based format derived from YAML, allowing researchers to extend and maintain the mapping documents with less effort. It also requires less experience in semantic web formats to deal with, and thus it was chosen to express the mapping rules. Using both the spreadsheet and the mapping document, the RMLMapper (36) tool was used to produce a set of triples, which were then loaded into a triple store for exploring and querying.