Are “rel” attributes, and linktypes in general, just document to document?
The vast majority of the rel values defined in HTML4 are from a document to a document. rel=”stylesheet” is a bit of an exception, as it from an HTML document to a style sheet, which is more like a set of styling rules and instructions than a “document” in the classical sense.Two more notable exceptions are rel=”copyright” and rel=”bookmark” which describe the relationship from the current document to (potentially) only part of a document.The ‘rev’ attribute adds an interesting perspective on this question. Specifically, 12.3.1 of HTML4 (http://www.w3.org/TR/html4/struct/links.html#rev-link) shows an example of two links one using rel and the other using rev which mean the same thing.Thus linktypes in general may be either from a whole document or part of a document to a whole document or a part of a document. For example, the rel-tag specification introduces the rel=”tag” value, and notes that it indicates a relation from a document or major portion thereof to a document.Finally, XFN
