template not operator support

Change-Id: Ifbeb468eb7eb79fbf950690b69d78095ed7051e1

specs/pike/template-not-operator-support.rst

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+..
+ This work is licensed under a Creative Commons Attribution 3.0 Unported
+ License.
+
+ http://creativecommons.org/licenses/by/3.0/legalcode
+
+=============================
+Template not operator Support
+=============================
+
+We would like the templates language to support the "not" operator in addition
+to "and" and "or" operators.
+
+Problem description
+===================
+
+Today the templates language support the "and" and "or" operators, but this is
+not enough.
+Many scenarios can't be described by those two operators, and thus we would
+like to add a support for the "not" operator.
+
+Proposed change
+===============
+
+Remark: positive vertex = vertex that has an edge with "is_deleted"=False property.
+        negative vertex = the opposite of positive vertex. Meaning that the
+                          vertex has only edges with "is_deleted"=True property.
+
+The following changes needs to be done to support the "not" operator.
+
+1. In the template validation. Check that the "Not" operator can appear only
+   in the following way:
+
+   "Not" operator can appear before edges.
+
+2. Scenario Evaluator:
+
+   check if "not" operator appears on an element, and add a property named
+   "negative_condition" on it, and updated it's "is_delete" property to True.
+
+3. Networkx Algorithm:
+
+   In the subgraph_matching method. If the match is not a "negative condition"
+   then perform regular subgraph_matching.
+   Otherwise, if the match is a "negative condition" then perform
+   subgraph_matching on a negative edges.
+
+
+Performance/Scalability Impacts
+-------------------------------
+
+The performance of the subgraph matching algorithm is a bit slower due to
+the steps above.
+
+
+Other deployer impact
+---------------------
+
+None
+
+Developer impact
+----------------
+
+None
+
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Primary assignee:
+    alexey_weyl <alexey.weyl@nokia.com>
+
+Work Items
+----------
+
+None
+
+Future lifecycle
+================
+
+None
+
+Dependencies
+============
+
+None
+
+Testing
+=======
+
+Added tests that are checking different uses of the "not" operator.
+
+Documentation Impact
+====================
+
+Added documentation in Vitrage:
+    https://github.com/openstack/vitrage/blob/master/doc/source/not_operator_support.rst
+
+References
+==========
+
+None