XML Signatures: Behind the Curtain - The Geek Part (Page 5 of 9 )
Note that in the examples that follow, it's OK to substitute in your mind the URL of some monopolistic software vendor in place of the W3C addresses. It'll make it seem more real. The following discussion borrows heavily from the candidate specifications, since they are vendor-neutral.
The first useful property of an XML signature is that it can be applied to any sort of digital content (sometimes called a data object), including XML. An XML signature may be applied to the content of one or more resources. Enveloped signatures are performed over data within the same XML document as the signature, so a detached signature is over data that is external to the signature's element itself. More specifically, the current XML signature specification defines an XML signature element type and an XML signature application; conformance requirements for each are specified in the document by way of schema definitions and prose, respectively.