authentication, message integrity, and non-repudiation. In addition to signature information, an XML Signature can also contain information describing the key used to sign the content. XLink Processing and Conformance Processing Dependencies: XLink processing depends on [XML], [XML Names], [XML Base], and [IETF RFC 2396] Markup Conformance: An XML element conforms to XLink if: it has a type attribute from the XLink namespace whose value is one of "simple", "extended", "locator", "arc", "resource", "title", or "none", and it adheres to the conformance constraints imposed by the chosen XLink element type, as prescribed in this specification. This specification imposes no particular constraints on DTDs; conformance applies only to elements and attributes. Application Conformance: An XLink application is any software module that interprets well-formed XML documents containing XLink elements and attributes, or XML information sets [XIS] containing information items and properties corresponding to XLink elements and attributes. Such an application is conforming if: it observes the mandatory conditions for applications ("must") set forth in this specification, and for any optional conditions ("should" and "may") it chooses to observe, it observes them in the way prescribed, and it performs markup conformance testing according to all the conformance constraints appearing in this specification. XLink Markup Design Link markup needs to be recognized reliably by XLink applications in order to be traversed and handled properly. XLink uses the mechanism described in the Namespaces in XML Recommendation [XML Names] to accomplish recognition of the constructs in the XLink vocabulary.