This paper proposes XConnector, a language for the creation of complex hypermedia relations with causal or constraint semantics. XConnector allows the definition of relations independently of which resources are related. Another feature is the specification of relation libraries, providing reuse in relationship definition. The main goal is to improve linking languages or the linking modules of hypermedia authoring languages in order to provide multimedia synchronization capabilities using links. Following this direction, an extension to W3C XLink is proposed, incorporating XConnector facilities.