This is a very short chapter, too.
This is a an ordinary DocBook link to the first chapter.
This is a new inline link to the first chapter.
And this is an XLink to the first chapter. XLink links are not checked during validation, while xml:id/linkend links are checked for ID/IDREF consistency. One place where the XLink-based, fragment identifier scheme is useful is when XInclude is being used, since XML ID/IDREF links cannot span XInclude boundaries. You can use whichever approach better suits your needs.