HTTP DELETE com.mycompany.myapp.Order|123/items
Request
body:
{
value: ...
}
Request headers:
- If-Match: (value of timestamp)
- where timestamp is as obtained from object representation
Request validation only 
custom header "X-ValidateOnly": "true"
Response if the object was removed from collection
modifies the collection
returns: 200 "OK"
Response if the object was not in collection
returns: 200 "OK"
Response if the object could not be removed from collection
returns: some sort of 4xx error
- Response 'Warning' header: error message
- ??? additionally, updated representation that has a message ???
Response if owning object or collection cannot be found
returns: 404
Response if the owning object has changed
returns: 409 "conflict"
header: "Last-Modified"