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

    record DocumentsWithWebsiteUsageSimilarities {
//      foreign key: Document.id ("document" data store)
        string documentId;
//      foreign key: Document.id ("document" data store)
        string otherDocumentId;
        union { null , float } covisitedSimilarity = null;
    }
    
}