see §4.2.7 of rfc 4287 spec. Note that the href, hreflang and lengtlength attributes of rfc 4287 have been moved to the content class and a content relation from the Link to a Content class has been made. The href is translated onto the awol:src relation of the Content class. A link is a reified relation between an entry an a content, for the purpose of adding some metadata such as a title. If it is a reified statement, it is a special type of such a statement, one that implies always the reified statement itself (see N3 rule)