namespace thr = "http://purl.org/syndication/thread/1.0"

include "atom.rnc" {
    start = in-reply-to | total
}
in-reply-to =
    element thr:in-reply-to { atomCommonAttributes, ref, href?, source?, type?, undefinedContent }
ref = attribute ref {  atomUri  }
href = attribute href { atomUri }
type = attribute type { atomMediaType }
source = attribute source { atomUri }
total = element thr:total { xsd:nonNegativeInteger }