Here are the REST services (all return xml or json).

Entity User Post Comment
create PUT /api/user/create?name=NAME&pwd=PASSWORD&mail=EMAIL PUT /api/post/create?title=TITLE&content=CONTENT&userId=USER_ID PUT /api/comment/create?author=NAME&content=CONTENT&postId=POST_ID
update POST /api/user/update/USER_ID?name=NAME&pwd=PASSWOR&mail=MAIL POST /api/post/update/POST_ID?userId=USER_ID&title=TITLE&content=CONTENT POST /api/comment/update/COMMENT_ID?author=NAME&content=CONTENT
delete DELETE /api/user/USER_ID DELETE /api/post/POST_ID DELETE /api/comment/COMMENT_ID
list GET /api/user/list GET /api/post/list GET /api/comment/list/POST_ID