Alternative Approaches - Non-XLink Solutions

XArc Gabe Beged-Dov originally created XArc in response to discussions on the XLink/XPointer (xlxp-dev) mailing list. XArc was a radical simplification, providing a from/to locator approach. It's been integrated with XLink to some extent.
RDF The W3C's Resource Description Format (RDF) is widely regarded as the hardest piece of XML. Nonetheless, it's simple foundations on directed graphs and freer rules for describing properties make it as capable, perhaps more capable, than XLink for describing complex relationships. For the most part, though, it's stuck in metadata.