Present HTML only supports typed links from whole documents to whole documents with the <link>
tag. For example, the tag <link rel="Contents" href="top.html">
specifies that the document "top.html" is a table of contents for the work that includes the document you are currently reading, and the tag <link rel="Next" href="chap3.html">
specifies that "chap3.html" is the next document in logical sequence after the one you are reading.
Typed links, while not really a part of Internet/HTML based hypertext systems were a common feature in pre-Internet hypertext systems such as Xanadu, NoteCards?, HyperWriter?, IBIS/gIBIS and others. While typed links can be very useful, the lack of a standardized set of link attributes such as "Supports Position"/"Refutes Position" as well as the difficulty of applying the attributes has always hindered the use typed links beyond prototyping purposes.