The new HyTime construct, nlink, will enable full compatibility between HTML links, TEI links, and HyTime links. This means that there is no reason not to use TEI's simple and elegant format for external links, which are already supported by systems vendors and can easily be made HyTime conformant. A contextual link occurs in a document and links the context where it occurs to some other information. An independent link be located near the linked data, and it may not. It may not even occur in the same document as either of the anchors that it links.
Independent links impose a heavier burden on a viewing application than contextual links do.
A contextual link only needs to be interpreted at the time it is displayed, while independent links need to be saved until one of their endpoints is displayed, at which point the link must be made available to the user. The TEI has not yet defined these identifiers, but CHIO is free to define its own for use within the museum community, if the TEI has not done so by the time implementation starts. As an example of what is involved in adding HyTime compliance to the TEI tags, the following example shows declarations for xptr and link elements that would enable HyTime processing of the link, as well as TEI processing. TEI attributes and element declarations have been omitted. The xptr element does not need to declare any of its attributes for determining the location designated, since the HyTime engine, once it knows that the element is a TEI pointer, will passs all the information about the element to a TEI processor, that will be responsible for resolving the pointer and returning the result back to HyTime.