Hi! I have an problem with the REST API of Object resources

I want to create an object to XWikiGroups.So I follow this http://www.xwiki.org/xwiki/bin/view/Documentation/UserGuide/Features/XWikiRESTfulAPI#HObjectresources ,

to Create an Object of “XWiki.XWikiGroups”, but I am failed for the class property of “value”. See it , I got none value .
Thanks for any help!

I guess you need to add a ‘property#member=XWiki.UserToAdd’
where “XWiki.UserToAdd” is the name of the user that will be member of this group.

I am not sure where the “value” comes from, or why it is necessary.