I call the rest API using this url
https:{server}/activities/service/atom2/service
the content
<entry xmlns="http://www.w3.org/2005/Atom" xmlns:snx="http://www.ibm.com/xmlns/prod/sn"><title>Overview</title>
<category scheme="http://www.ibm.com/xmlns/prod/sn/type" term="activity" />
<content>Here they are</content>
<category term="Vandals" />
<snx:duedate>2012-01-31T05:00:00Z</snx:duedate>
</entry>
bodycontenttype =application/atom+xml
contenttype = text/xml