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

    import idl "DocumentClasses.avdl";

    record DocumentToDocumentClasses {
//      foreign key: Document.id ("document" data store)
        string documentId;
//      Information about the classes given document belongs to
//      There might be many parallel classification systems given document might belong to 
//      (e.g. classification w.r.t. importance of the document, classification w.r.t. popularity).
        union { null , DocumentClasses } classes = null;
    }
}