@namespace("eu.dnetlib.iis.documentssimilarity.schemas")
protocol IIS{
    import idl "../importer/Person.avdl";

    record DocumentMetadata {
        string id;
        union { null , string } title = null;
        union { null , string } abstract = null;
        union { null , array<string> } keywords = null;
        union { null , array<eu.dnetlib.iis.importer.schemas.Person> } authors = null;
    }
}