Is it possible to add "" or in the head?

Hi there, in my very early days of html a lot of authors and I used those elements in the head to build up the structure of the whole site. Search engines were able to understand and follow them. The goal was, to show the structure from the authors view and to help UAs to show up the structure. Further it was user-friendly, too.

<link rel="start">
<link rel="index">
<link rel="contents">
<link rel="chapter">
<link rel="next">
<link rel="prev">

So my question(s) is: how to add them (or are they unnecessary nowadays?)