@namespace("eu.dnetlib.iis.websiteusage.schemas")
protocol IIS{
    
    record DataSetWebsiteUsageSimilarities {
//      coefficient from [0, 1] range,
//      the greater the number, the more similar the datasets w.r.t
//      being visited together
        union { null , float } covisitedSimilarity = null;
//      some other similarity metrics, to be specified by NKUA
    }

}