LinkTypes Attribute Type

The LinkTypes Attribute Type is a data type defined by XHTML Modularisation 1.1, declared in the DTD as XML 1.0 type NMTOKENS.
Reference: *W3C - XHTML Modularisation 1.1 - Attribute Types

Specific Attributes with Type LinkTypes

1. rel:
   This is declared on the elements: link, a
2. rev:
   This is declared on the elements: link, a

Common Attributes with Type LinkTypes

There are no Common Attributes with type LinkTypes.

Attribute Value for Type LinkTypes

A space-separated list of one or more link types

A link type is a string describing the relationship between two documents (or other resources). Link types are case-insensitive. The W3C's list of recognised LinkTypes is shown below (ref: *Defining Abstract Modules - Attribute Types):

alternate

an alternative version of a document
e.g. if used in association with the hreflang attribute, it specifies a translated version
or if used with the media attribute, it specifies a version to be used with the medium/media stated

stylesheet

indicates an external style sheet
may be used in conjunction with the 'alternate' link type to specify alternative style sheets for a document

start

indicates the first document in a set of documents

next

refers to the next document in a series of documents
this next document may possibly be pre-loaded in order to decrease the apparent load time

prev

refers to the previous document in a series of documents

contents

indicates a document containing a Table of Contents

index

indicates a document containing an Index for the current document

glossary

indicates a document containing a Glossary for the current document

copyright

a copyright statement applying to the current document

chapter

a chapter within a set of documents

section

a section within a set of documents

subsection

a subsection within a set of documents

appendix

an appendix to a set of documents

help

a help document

bookmark

a bookmark within a document
This is a link to a particular point within a long document (which may contain several bookmarks).
The bookmark may be labelled using the title attribute.

Other link types are routinely used by some user agents (for example, *Opera additionally recognises "home", "search", "up", "first", "last" and "author", which it uses in its "Navigation bar"). However, the XHTML specification states that any link types which are not in the recognised list above should be described in a metadata profile and linked to the document using the profile attribute of the head element.

The XHTML/HTML specification is remarkably vague about what constitutes such a metadata profile and their use is not widespread - for example: even though the "home" link type is used regularly throughout the *Opera site, there is no profile attribute specified on the head element to describe its meaning. I guess the meaning of "home" is pretty obvious, but I do think that it is a good idea in principle to include profile information.

The lack of a defined structure for such profiles has led to candidate formats being proposed from outside the W3C - notably, Tantek Çelik's *XHTML Meta Data Profiles (XMDP). Since I am using Opera-compatible link types on this site and could not source a profile from Opera itself, I have created my own XMDP to describe the extra types; the description for meta "copyright" is also included, since all meta properties (and schemes) should also be described in a profile (ref, for HTML: *HTML 4.01 - Meta Data).