Merge pull request #89 from keptn/fix/6106/added_example_of_AND_for_SLO

chore: added example of criteria AND in SLO  (keptn/keptn/#6106)

service_level_objective.md

@@ -91,9 +91,25 @@ objectives:
   key_sli: true
 ```
 
-Further assume, that in the previous evaluation error_rate was 5%. The upper limit for pass is 5.5% (5 + 10%). The following list shows the evaluation results for all possible error_rate values.
-*   pass: <= 5.5%
-*   fail: > 5.5%
+Further assume, that in the previous evaluation the metric response_time_p95 was 5. The upper limit for pass is 5.5 (5 + 10%). The evaluation results for all possible values would be:
+*   pass: <= 5.5
+*   fail: > 5.5
+
+Listed criteria are combined using a logical AND, so if we consider the pass criteria in our example both  "<=+10%" and  "<600" needs to be satisfied.
+To list multiple criteria  (logical OR) it is enough to list them in different criteria element, for instance the following would enforce for response time not to be higher than 10% compared to the previous value or to be greater than 600:
+
+```yaml
+objectives:
+- sli: response_time_p95
+  displayName: "Response Time P95"
+  pass:
+  - criteria:
+    - "<=+10%"
+  - criteria:  
+    - "<600"
+  weight: 2
+  key_sli: true
+```
 
 ## Scoring