Help needed with some errors and checking a docbook5 with xmllint

Hi, need help checking a docbook5 xml file.

When I run 

´´´    
xsltproc --xinclude --output Test.html /home/mepi/Downloads/docbook-xsl-1.79.2/xhtml/
docbook.xsl MyBook.xml 


I get following Error:

´´´
MyBook.xml:60: namespace error : Namespace prefix xl for href on link is not defined 
       If not, see <link xl:href="http://www.gnu.org/licenses/"> <emphasis>the 
                                                                ^ MyBook.xml:69: namespace error : Namespace prefix 
xl for href on link is not defined        <link xl:href="http://creativecommons.org/about/
licenses/"> <emphasis>th ´´´
         
*What do I wrong?*
                                                        ^

When I try to check my File MyBook.xml with xmllint,

´´´
xmllint --relaxng /usr/share/xml/docbook5/schema/rng/5.1/docbook.rng MyBook.xml


I get following messages:

´´´
MyBook.xml:18: element info: Relax-NG validity error : Element book has extra content: 
info 
MyBook.xml:13: element book: Relax-NG validity error : Expecting element abstract, got 
book 

MyBook.xml:13: element book: Relax-NG validity error : Did not expect element book there 

MyBook.xml:13: element book: Relax-NG validity error : Expecting element audiodata, got 
book 

MyBook.xml:13: element book: Relax-NG validity error : Expecting element example, got 
book 

MyBook.xml fails to validate´´´

*What does the messages above mean?*

The MyBook.xml file looks like:

´´´
 1  <?xml version="1.0" encoding="utf-8"?>
 2  
 3  <!DOCTYPE book [
 4		<!ENTITY % MyEntitys_ent SYSTEM "MyEntitys.ent">
 5		%MyEntitys_ent;
 6  ]>
 7
 8  <book
 9     version="5.0"
10     xmlns="http://docbook.org/ns/docbook" 
11     xmlns:xi="http://www.w3.org/2001/XInclude" 
12      xmlns:xlink="http://www.w3.org/1999/xlink" 
13      xml:lang="en"> 
14
15
16   <title>My Book</title>
17 
18    <info>
19
20      <legalnotice>
21
22        <para>
23          My Text
24        </para>
25
26      </legalnotice>
27
28      <copyright>
29        <year>2010-2012</year>
30        <holder>Mr. X and me</holder>
31      </copyright>
32
33    </info>
...
60      see <link xl:href="http://www.gnu.org/licenses/"> <emphasis>the GNU
61      homepage</emphasis></link>.
...211  </book>
´´´

Thanks
Pierre