@namespace("eu.dnetlib.iis.documentssimilarity.schemas")
protocol IIS{

    record DocumentSimilarity {
//      document identifier
//      foreign key: Document.id ("updated document" data store)
        string documentId;
//      identifier of a similar document,
//      foreign key: Document.id ("updated document" data store)
        string otherDocumentId;
//      level of similarity: coefficient from [0, 1] range,
//      the greater the number, the more similar the documents
        union { null , float } similarity = null;
    }
}