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3. Component Description

The ONAP Policy Framework is a comprehensive policy design, deployment, and execution environment. The Policy Framework is the decision making component in an ONAP system. It allows you to specify, deploy, and execute the governance of the features and functions in your ONAP system, be they closed loop, orchestration, or more traditional open loop use case implementations. The Policy Framework is the component that is the source of truth for all policy decisions

Please see the TOSCA Policy Primer page for an introduction to TOSCA policy concepts. See the Policy Design and API flow page for a description of the component interactions.

TOSCA defines a PolicyType, the definition of a type of policy that can be applied to a service. It also defines a Policy, the definition of an instance of a PolicyType. In the Policy Framework, we must handle and manage these TOSCA definitions and tie them to real implementations of policies that can run on PDPs.

Each TOSCA PolicyType must have a corresponding PolicyTypeImpl in the Policy Framework. The TOSCA PolicyType definition can be used to create a TOSCA Policydefinition, either directly by the Policy Framework, by CLAMP, or by some other system. Once the Policy artifact exists, it can be used together with the PolicyTypeImpl artifact to create a PolicyImpl artifact. A PolicyImpl artifact is an executable policy implementation that can run on a PDP.

The TOSCA PolicyType artifact defines the external characteristics of the policy; defining its properties, the types of entities it acts on, and its triggers.  A PolicyTypeImpl artifact is an XACML, Drools, or APEX implementation of that policy definition. PolicyType and PolicyTypeImpl artifacts may be preloaded, may be loaded manually, or may be created using the Lifecycle API. Alternatively, PolicyType definitions may be loaded over the Lifecycle API for preloaded PolicyTypeImpl artifacts. A TOSCA PolicyType artifact can be used by clients (such as CLAMP or CLI tools) to create, parse, serialize, and/or deserialize an actual Policy.

The TOSCA Policy artifact is used internally by the Policy Framework, or is input by CLAMP or other systems. This artifact specifies the values of the properties for the policy and specifies the specific entities the policy acts on. Policy Design uses the TOSCA Policy artifact and the PolicyTypeImpl artifact to create an executable PolicyImpl artifact. 

Internally, Policy has three main functional areas: Policy Development; Policy Administration; Policy Decision Execution.

Policy Development abstracts persistence and supports the creation of policies/policy types.

Policy Administration also abstracts persistence (from a different user roles). It's main purposes are to ensure that policies are allocated correctly and to manage the life-cycle of policies.

Policy Decision Execution is where policy decisions are made, i.e. where the policy logic executes. Three languages are used to describe policies in ONAP: XACML; Drools; APEX. Policy designers may select the language that is most appropriate to their use case. The policies are interpreted and executed by a language specific PDP. Where necessary additional PDP may be added, thus allowing for new policy languages.

Policy Enforcement is not handled by the Policy Framework. Enforcement is handled by either the originator of a decision query, or by a reaction to a policy trigger.

4. Known System Limitations

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