Open Stack

Hi folks:

    I face a problem when I insert a rule into Congress. I want to find out
all of the volumes that are not available status, so I draft a rule like
this:

    error(id) :- cinder:volumes(id=id), not cinder:volumes(id=id,
status="available")

    But when I create the rule, a error is raised:

(openstack) congress policy rule create chenrui_p "error(id) :-
cinder:volumes(id=id),not cinder:volumes(id=id, status=\"available\")"
ERROR: openstack Syntax error for rule::Errors: Could not reorder rule
error(id) :- cinder:volumes(id, _x_0_1, _x_0_2, _x_0_3, _x_0_4, _x_0_5,
_x_0_6, _x_0_7, _x_0_8), not cinder:volumes(id, _x_1_1, _x_1_2,
"available", _x_1_4, _x_1_5, _x_1_6, _x_1_7, _x_1_8).  Unsafe lits: not
cinder:volumes(id, _x_1_1, _x_1_2, "available", _x_1_4, _x_1_5, _x_1_6,
_x_1_7, _x_1_8) (vars set(['_x_1_2', '_x_1_1', '_x_1_6', '_x_1_7',
'_x_1_4', '_x_1_5', '_x_1_8'])) (HTTP 400) (Request-ID:
req-1f4432d6-f869-472b-aa7d-4cf78dd96fa1)

    I check the Congress policy docs [1], looks like that the rule don't
break any syntax restrictions.

    If I modify the rule like this, it works:

(openstack) congress policy rule create chenrui_p "error(x) :-
cinder:volumes(x, _x_0_1, _x_0_2, _x_0_3, _x_0_4, _x_0_5, _x_0_6, _x_0_7,
_x_0_8),not cinder:volumes(x, _x_0_1, _x_0_2, \"available\",_x_0_4, _x_0_5,
_x_0_6, _x_0_7, _x_0_8)"
+---------+------------------------------------------------------------------------------------------------+
| Field   | Value
                               |
+---------+------------------------------------------------------------------------------------------------+
| comment | None
                                |
| id      | ad121e09-ba0a-45d6-bd18-487d975d5bf5
                                |
| name    | None
                                |
| rule    | error(x) :-
                               |
|         |     cinder:volumes(x, _x_0_1, _x_0_2, _x_0_3, _x_0_4, _x_0_5,
_x_0_6, _x_0_7, _x_0_8),         |
|         |     not cinder:volumes(x, _x_0_1, _x_0_2, "available", _x_0_4,
_x_0_5, _x_0_6, _x_0_7, _x_0_8) |
+---------+------------------------------------------------------------------------------------------------+

    I'm not sure this is a bug or I miss something from docs, so I need
some feedback from mail list.
Feel free to discuss about it.


[1]:
http://congress.readthedocs.org/en/latest/policy.html#datalog-syntax-restrictions


Best Regards.
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