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Let's take a look what are dependencies between them:
As you can see on scheme to 
To deploy* closed loop Clamp uses DCEA_INVENTORY_BLUEPRINT.
Each node that is deployed has to have specified it's policy type.
From Analytic Microservice perspective policy type is a scheme of how it's configuration should look like.
If node doesn't have specified policy type Clamp assumes it's default one onap.policy.monitoring.cdap.tca.hi.lo.app
Policy types described inside policies.yml can have sub-nodes. Those sub-nodes are data types. They're described inside artifact data.yml.
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Dublin constraint is that both data.yml and policies.yml are hardcoded and can't be changed/extended in runtime.
Script policy_create.py is able to create new policy type and data type that could be add to policies.yml and data.yml.
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- node_types - containing root node and policy.nodes.my_custom_policy_type. This node is actually a policy_type. In future it should derive from onap.policies.Monitoring instead of policy.nodes.Root
- data_types - specifying data types (and sub-data types) used in node_type (policy_type)
Note: The default output_policy.yaml generated requires manual update before it can be used in rest of CL flow design. Follow steps documented here - Onboarding steps for DCAE MS through SDC/Policy/CLAMP (Dublin)#PolicyTypeCreation(Developmentphase) to make updates