Updated Architecture Chapter 1
Updated TOSCA policy primer to include image.
Updated Architecture doc to fix links.
Updated chapter 1 of architecture doc.
Fixed hierarchy problem with chapter levels in architecture doc.
Issue-ID: POLICY-1676
Change-Id: I25868082465508d214b4bf1559e5aa8ce84fb069
Signed-off-by: liamfallon <liam.fallon@est.tech>
diff --git a/docs/architecture/architecture.rst b/docs/architecture/architecture.rst
index e0b4048..b1c66d1 100644
--- a/docs/architecture/architecture.rst
+++ b/docs/architecture/architecture.rst
@@ -4,7 +4,7 @@
Architecture
-------------
+############
Abstract
@@ -17,15 +17,15 @@
of various types using the framework.
.. contents::
- :depth: 4
+ :depth: 6
-1. Overview
+1. Overview
===========
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 <https://www.onap.org/wp-content/uploads/sites/20/2017/12/ONAP_CaseSolution_Architecture_120817_FNL.pdf>`__.
+system <https://www.onap.org/wp-content/uploads/sites/20/2018/11/ONAP_CaseSolution_Architecture_112918FNL.pdf>`__.
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.
@@ -123,7 +123,7 @@
The diagram below shows the architecture of the ONAP Policy Framework at
its highest level.
-.. image:: highest.png
+.. image:: images/highest.png
The *PolicyDevelopment* component implements the functionality for
development of policy types and policies. *PolicyAdministration* is
@@ -136,10 +136,10 @@
*PolicyExecution* is the set of PDPs running in the ONAP system and is
responsible for making policy decisions and for managing the
administrative state of the PDPs as directed
-by \ *PolicyAdministration.*
+by \ *PolicyAdministration.*
*PolicyDevelopment* creates policy artifacts and supporting information
-in the policy database. \ *PolicyAdministration* reads those artifacts
+in the policy database. \ *PolicyAdministration* reads those artifacts
and the supporting information from the policy database whilst deploying
policy artifacts. Once the policy artifacts are deployed,
*PolicyAdministration* handles the run-time management of the PDPs on
@@ -152,7 +152,7 @@
inspired by `RFC-2753 <https://tools.ietf.org/html/rfc2753>`__ and
`RFC-3198 <https://tools.ietf.org/html/rfc3198>`__.
-.. image:: detailed.png
+.. image:: images/detailed.png
*PolicyDevelopment* provides a
`CRUD <https://en.wikipedia.org/wiki/Create,_read,_update_and_delete>`__
@@ -192,7 +192,7 @@
*PolicyExecution* is the set of running PDPs that are executing
policies, logically partitioned into PDP groups and subgroups.
-.. image:: execution.png
+.. image:: images/execution.png
The figure above shows how *PolicyExecution* looks at run time with PDPs
running in Kubernetes. A *PDPGroup* is a purely logical construct that
@@ -202,7 +202,7 @@
`Deployment <https://kubernetes.io/docs/concepts/workloads/controllers/deployment/>`__.
PDPs are defined as Kubernetes
`Pods <https://kubernetes.io/docs/concepts/workloads/pods/pod/>`__. At
-run time, the actual number of PDPs in each *PDPSubGroup* is specified
+run time, the actual number of PDPs in each *PDPSubGroup* is specified
in the configuration of the *Deployment* of that *PDPSubGroup* in
Kubernetes. This structuring of PDPs is required because, in order to
simplify deployment and scaling of PDPs in Kubernetes, we gather all the
@@ -236,12 +236,12 @@
model and is used by *PolicyDevelopment*, *PolicyDeployment,* and
*PolicyExecution.*
-.. image:: objectmodel1.png
+.. image:: images/objectmodel1.png
The UML class diagram above shows the portion of the Policy Framework
Object Model that applies to *PolicyDeployment* and *PolicyExecution.*
-.. image:: objectmodel2.png
+.. image:: images/objectmodel2.png
The UML class diagram above shows the portion of the Policy Framework
Object Model that applies to *PolicyDevelopment* and *PolicyDeployment.*
@@ -262,7 +262,7 @@
implementation development is done by an experienced developer.
2.2.1 Policy Type Design
-~~~~~~~~~~~~~~~~~~~~~~~~
+^^^^^^^^^^^^^^^^^^^^^^^^
Policy Type Design is the task of creating policy types that capture the
generic and vendor independent aspects of a policy for a particular
@@ -271,7 +271,7 @@
concrete policies.
All policy types must implement the ONAP Policy Framework *PolicyType*
-interface. This interface allows \ *PolicyDevelopment* to manage policy
+interface. This interface allows \ *PolicyDevelopment* to manage policy
types and to generate policies from these policy types in a uniform way
regardless of the domain that the policy type is addressing or the PDP
technology that will execute the policy. The interface is used by
@@ -279,12 +279,12 @@
the structure, type, and definition of the model information that must
be supplied to the policy type to generate a concrete policy.
-A \ *PolicyTypeImpl* is developed for a certain type of PDP (for example
+A \ *PolicyTypeImpl* is developed for a certain type of PDP (for example
XACML oriented for decision policies or Drools rules oriented for ECA
policies). The design environment and tool chain for a policy type is
specific for the type of policy being designed.
-The \ *PolicyTypeImpl* implementation (or raw policy) is the
+The \ *PolicyTypeImpl* implementation (or raw policy) is the
specification of the specific rules or tasks, the flow of the policy,
its internal states and data structures and other relevant information.
A *PolicyTyp*\ e\ *Impl* is specific to a PDP technology, that is XACML,
@@ -299,19 +299,19 @@
implementations, to determine the model information, rules, or tasks
that they require, to specialize policy flow, and to generate policies
from policy types. This API is used by the ONAP Policy Framework and
-other components such as \ *PolicyDistribution* to create policies from
+other components such as \ *PolicyDistribution* to create policies from
policy types.
Consider a policy type created for managing faults on vCPE equipment in
a vendor independent way. The policy type captures the generic logic
required to manage the faults and specifies the vendor specific
information that must be supplied to the type for specific vendor vCPE
-VFs. The actual vCPE policy that is used for managing particular vCPE
+VFs. The actual vCPE policy that is used for managing particular vCPE
equipment is created by setting the parameters specified in the policy
type together with the specific modeled information, rules and tasks in
the policy type implementation for that vendor model of vCPE.
-2.2.1 Generating Policy Types
+2.2.2 Generating Policy Types
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
It is possible to generate policy types using MDD (Model Driven
@@ -333,8 +333,8 @@
The GUI implementation in another ONAP component such as SDC DCAE-DS
uses the *API_User* API to create and edit ONAP policy types.
-2.2.1.2 Programming Policy Type Implementations
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+2.2.1.1 Programming Policy Type Implementations
+"""""""""""""""""""""""""""""""""""""""""""""""
For skilled developers, the most straightforward way to create a policy
type is to program it. Programming a policy type might simply mean
@@ -347,31 +347,31 @@
under source control in git. This Eclipse project is structured
correctly for creating implementations for a specific type of PDP. It
includes the correct POM files for generating the policy type
-implementation and has editors and perspectives that aid programmers in
+implementation and has editors and perspectives that aid programmers in
their work
2.2.2 Policy Design
-~~~~~~~~~~~~~~~~~~~
+^^^^^^^^^^^^^^^^^^^
The *PolicyCreation* function of *PolicyDevelopment* creates policies
-from a policy type. The information expressed during policy type design
+from a policy type. The information expressed during policy type design
is used to parameterize a policy type to create an executable policy. A
service designer and/or operations team can use tooling that reads the
TOSCA Policy Type specifications to express and capture a policy at its
highest abstraction level. Alternatively, the parameter for the policy
can be expressed in a raw JSON or YAML file and posted over the policy
-design API described on the `Model driven Control Loop
+design API described on the `Model driven Control Loop
Design <file://localhost/display/DW/Model+driven+Control+Loop+Design>`__
page.
-A number of mechanisms for policy creation are supported in ONAP. The
+A number of mechanisms for policy creation are supported in ONAP. The
process in *PolicyDevelopment* for creating a policy is the same for all
mechanisms. The most general mechanism for creating a policy is using
the RESTful *Policy Design API*, which provides a full interface to the
policy creation support of *PolicyDevelopment*. This API may be
-exercised directly using utilities such as *curl*. \ *PolicyDevelopment*
+exercised directly using utilities such as *curl*. \ *PolicyDevelopment*
provides a command line tool that is a loose wrapper around the API. It
-also provides a general purpose Policy GUI in the ONAP Portal for policy
+also provides a general purpose Policy GUI in the ONAP Portal for policy
creation, which again is a general purpose wrapper around the policy
creation API. The Policy GUI can interpret any TOSCA Model ingested and
flexibly presents a GUI for a user to create policies from. The
@@ -388,7 +388,7 @@
modification supported by the ONAP Policy Framework.
2.2.2.1 Policy Design in the ONAP Policy Framework
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+""""""""""""""""""""""""""""""""""""""""""""""""""
Policy creation in *PolicyDevelopment* follows the general sequence
shown in the sequence diagram below. An *API_USER* is any component that
@@ -398,26 +398,26 @@
A *PolicyDevAPIUser* first gets a reference to and the metadata for the
Policy type for the policy they want to work on from
-*PolicyDevelopment*. \ *PolicyDevelopment* reads the metadata and
+*PolicyDevelopment*. \ *PolicyDevelopment* reads the metadata and
artifact for the policy type from the database. The *API_User* then asks
-for a reference and the metadata for the policy. \ *PolicyDevelopment*
+for a reference and the metadata for the policy. \ *PolicyDevelopment*
looks up the policy in the database. If the policy already
-exists, \ *PolicyDevelopment* reads the artifact and returns the
-reference of the existing policy to the \ *PolicyDevAPIUser* with the
+exists, \ *PolicyDevelopment* reads the artifact and returns the
+reference of the existing policy to the \ *PolicyDevAPIUser* with the
metadata for the existing policy. If the policy does not
-exist, \ *PolicyDevelopment* creates and new reference and metadata and
-returns that to the \ *API_User*.
+exist, \ *PolicyDevelopment* creates and new reference and metadata and
+returns that to the \ *API_User*.
-The \ *PolicyDevAPIUser* may now proceed with a policy specification
+The \ *PolicyDevAPIUser* may now proceed with a policy specification
session, where the parameters are set for the policy using the policy
-type specification. Once the \ *PolicyDevAPIUser* is happy that the
+type specification. Once the \ *PolicyDevAPIUser* is happy that the
policy is completely and correctly specified, it
-requests \ *PolicyDevelopment* to create the
-policy. \ *PolicyDevelopment* creates the policy, stores the created
+requests \ *PolicyDevelopment* to create the
+policy. \ *PolicyDevelopment* creates the policy, stores the created
policy artifact and its metadata in the database.
2.2.2.2 Model Driven VF (Virtual Function) Policy Design via VNF SDK Packaging
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
VF vendors express policies such as SLA, Licenses, hardware placement,
run-time metric suggestions, etc. These details are captured within the
@@ -434,7 +434,7 @@
read from a CSAR received from SDC.
*PolicyDesign* uses the *PolicyDistribution* component for managing
-SDC-triggered policy creation and update requests. *PolicyDistribution*
+SDC-triggered policy creation and update requests. *PolicyDistribution*
is an *API_User*, it uses the Policy Design API for policy creation and
update. It reads the information it needs to populate the policy type
from a TOSCA specification in a CSAR received from SDC and then uses
@@ -445,16 +445,16 @@
Distribution Software
Architecture <file://localhost/display/DW/Policy+Platform+-+SDC+Service+Distribution+Software+Architecture>`__
-In Step 4 above, the \ *PolicyDesign* must download the CSAR file. If
+In Step 4 above, the \ *PolicyDesign* must download the CSAR file. If
the policy is to be composed from the TOSCA definition, it must also
parse the TOSCA definition.
-In Step 9 above, the \ *PolicyDesign* must send back/publish status
+In Step 9 above, the \ *PolicyDesign* must send back/publish status
events to SDC such as DOWNLOAD_OK, DOWNLOAD_ERROR, DEPLOY_OK,
DEPLOY_ERROR, NOTIFIED.
-2.2.2.4 Scripted Model Driven Policy Design
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+2.2.2.3 Scripted Model Driven Policy Design
+"""""""""""""""""""""""""""""""""""""""""""
Service policies such as optimization and placement policies can be
specified as a TOSCA Policy at design time. These policies use a TOSCA
@@ -469,7 +469,7 @@
the Policy API to create the policy.
2.2.3 Policy Design Process
-~~~~~~~~~~~~~~~~~~~~~~~~~~~
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
All policy types must be certified as being fit for deployment prior to
run time deployment. In the case of design-time via the SDC application,
@@ -520,7 +520,7 @@
are explained.
2.3.1 Policy Framework Services
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The ONAP Policy Framework follows the architectural approach for micro
services recommended by the `ONAP Architecture
@@ -529,7 +529,7 @@
The ONAP Policy Framework defines `Kubernetes
Services <https://kubernetes.io/docs/concepts/services-networking/service/>`__
to manage the life cycle of Policy Framework executable components at
-runtime. A Kubernetes service allows, among other parameters, the
+runtime. A Kubernetes service allows, among other parameters, the
number of instances (pods in Kubernetes terminology) that should be
deployed for a particular service to be specified and a common endpoint
for that service to be defined. Once the service is started in
@@ -572,7 +572,7 @@
for each domain for which there are policies.
2.3.2 The Policy Framework Information Structure
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The following diagram captures the relationship between Policy Framework
concepts at run time.
@@ -591,31 +591,31 @@
The diagram above gives an indicative structure of the run time topology
information in the Policy Framework database. Note that
-the \ *PDP_SUBGROUP_STATE* and \ *PDP_STATE* fields hold state
+the \ *PDP_SUBGROUP_STATE* and \ *PDP_STATE* fields hold state
information for life cycle management of PDP groups and PDPs.
2.3.3 Startup, Shutdown and Restart
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This section describes the interactions between Policy Framework
components themselves and with other ONAP components at startup,
shutdown and restart.
2.3.3.1 PAP Startup and Shutdown
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+""""""""""""""""""""""""""""""""
The sequence diagram below shows the actions of the PAP at startup.
The PAP is the run time point of coordination for the ONAP Policy
Framework. When it is started, it initializes itself using data from the
-database. It then waits for periodic PDP status updates and for
+database. It then waits for periodic PDP status updates and for
administration requests.
PAP shutdown is trivial. On receipt or a shutdown request, the PAP
completes or aborts any ongoing operations and shuts down gracefully.
2.3.3.2 PDP Startup and Shutdown
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+""""""""""""""""""""""""""""""""
The sequence diagram below shows the actions of the PDP at startup. See
also Section 4 of the `Policy Design and API Flow for Model Driven
@@ -623,7 +623,7 @@
Loop <file://localhost/display/DW/Policy+Design+and+API+Flow+for+Model+Driven+Control+Loop>`__
page for the API used to implement this sequence.
-At startup, the PDP initializes itself. At this point it is in PASSIVE
+At startup, the PDP initializes itself. At this point it is in PASSIVE
mode. The PDP begins sending periodic Status messages to the PAP.
The first Status message initializes the process of loading the correct
@@ -633,7 +633,7 @@
ongoing policy executions and shuts down gracefully.
2.3.4 Policy Execution
-~~~~~~~~~~~~~~~~~~~~~~
+^^^^^^^^^^^^^^^^^^^^^^
Policy execution is the execution of a policy in a PDP. Policy
enforcement occurs in the component that receives a policy decision.
@@ -661,7 +661,7 @@
================== ===========================================================================================================================================================================================================================================================================================================================
2.3.5 Policy Lifecycle Management
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Policy lifecycle management manages the deployment and life cycle of
policies in PDP groups at run time. Policy sets can be deploy at run
@@ -669,7 +669,7 @@
state for minor/patch version upgrades and rollbacks.
2.3.5.1 Load/Update Policies on PDP
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+"""""""""""""""""""""""""""""""""""
The sequence diagram below shows how policies are loaded or updated on a
PDP.
@@ -696,7 +696,7 @@
beings to execute policies in the specified mode (see section 2.3.4).
2.3.5.2 Policy Rollout
-^^^^^^^^^^^^^^^^^^^^^^
+""""""""""""""""""""""
A policy set steps through a number of life cycle modes when it is
rolled out.
@@ -723,7 +723,7 @@
TEST, or even PASSIVE mode at any time if problems arise.
2.3.5.3 Policy Upgrade and Rollback
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+"""""""""""""""""""""""""""""""""""
There are a number of approaches for managing policy upgrade and
rollback.
@@ -736,7 +736,7 @@
set into ACTIVE mode immediately. The advantage of this approach is that
the approach is straightforward. The obvious disadvantage is that the
PDP group is not executing on the target environment while the new
-policy set is in PASSIVE, TEST, and SAFE mode.
+policy set is in PASSIVE, TEST, and SAFE mode.
A second manner to tackle upgrade and rollback is to use a spare-wheel
approach. An special upgrade PDP group service is set up as a K8S
@@ -756,7 +756,7 @@
the complexity of implementation in PDPs significantly.
2.3.6 Policy Monitoring
-~~~~~~~~~~~~~~~~~~~~~~~
+^^^^^^^^^^^^^^^^^^^^^^^
PDPs provide a periodic report of their status to the PAP. All PDPs
report using a standard reporting format that is extended to provide
@@ -777,7 +777,7 @@
===================== ===============================================================================
2.3.7 PEP Registration and Enforcement Guidelines
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
In ONAP there are several applications outside the Policy Framework that
enforce policy decisions based on models provided to the Policy
@@ -809,7 +809,7 @@
PDP Group A group of PDPs that execute the same set of policies
Policy Development The development environment for policies
Policy Type A generic prototype definition of a type of policy in TOSCA, see the `TOSCA Policy Primer <file://localhost/display/DW/TOSCA+Policy+Primer>`__
-Policy An executable policy defined in TOSCA and created using a Policy Type, see the `TOSCA Policy Primer <file://localhost/display/DW/TOSCA+Policy+Primer>`__
+Policy An executable policy defined in TOSCA and created using a Policy Type, see the `TOSCA Policy Primer <file://localhost/display/DW/TOSCA+Policy+Primer>`__
Policy Set A set of policies that are deployed on a PDP group. One and only one Policy Set is deployed on a PDP group
================================= =========================================================================================================================================================
diff --git a/docs/architecture/images/ToscaPolicyStructure.png b/docs/architecture/images/ToscaPolicyStructure.png
new file mode 100644
index 0000000..f1e6cb4
--- /dev/null
+++ b/docs/architecture/images/ToscaPolicyStructure.png
Binary files differ
diff --git a/docs/architecture/detailed.png b/docs/architecture/images/detailed.png
similarity index 100%
rename from docs/architecture/detailed.png
rename to docs/architecture/images/detailed.png
Binary files differ
diff --git a/docs/architecture/execution.png b/docs/architecture/images/execution.png
similarity index 100%
rename from docs/architecture/execution.png
rename to docs/architecture/images/execution.png
Binary files differ
diff --git a/docs/architecture/highest.png b/docs/architecture/images/highest.png
similarity index 100%
rename from docs/architecture/highest.png
rename to docs/architecture/images/highest.png
Binary files differ
diff --git a/docs/architecture/objectmodel1.png b/docs/architecture/images/objectmodel1.png
similarity index 100%
rename from docs/architecture/objectmodel1.png
rename to docs/architecture/images/objectmodel1.png
Binary files differ
diff --git a/docs/architecture/objectmodel2.png b/docs/architecture/images/objectmodel2.png
similarity index 100%
rename from docs/architecture/objectmodel2.png
rename to docs/architecture/images/objectmodel2.png
Binary files differ
diff --git a/docs/architecture/tosca-policy-primer.rst b/docs/architecture/tosca-policy-primer.rst
new file mode 100644
index 0000000..686d356
--- /dev/null
+++ b/docs/architecture/tosca-policy-primer.rst
@@ -0,0 +1,79 @@
+.. This work is licensed under a
+.. Creative Commons Attribution 4.0 International License.
+.. http://creativecommons.org/licenses/by/4.0
+
+.. _tosca-label:
+
+TOSCA Policy Primer
+-------------------
+
+.. contents::
+ :depth: 2
+
+This page gives a short overview of how Policy is modelled in the
+`TOSCA Simple Profile in YAML <http://docs.oasis-open.org/tosca/TOSCA-Simple-Profile-YAML/v1.1/TOSCA-Simple-Profile-YAML-v1.1.pdf>`__.
+
+TOSCA defines three concepts for Policy: Policy Type, Policy, and Trigger.
+
+.. image:: images/ToscaPolicyStructure.png
+ :width: 800
+
+Policy Type
+~~~~~~~~~~~
+
+A Policy Type is used to specify the types of policies that may be used in a service. The parameter definitions
+for a policy of this type, the entity types to which it applies, and what triggers policies of this type may be
+specified.
+
+
+The types of policies that are used in a service are defined in the policy_types section of the TOSCA service template
+as a Policy Type. More formally, TOSCA defines a Policy Type as an artifact that "defines a type of requirement that
+affects or governs an application or service’s topology at some stage of its life cycle, but is not explicitly part of
+the topology itself". In the definition of a Policy Type in TOSCA, you specify:
+
+* its properties, which define the type of configuration parameters that the policy takes
+* its targets, which define the node types and/or groups to which the policy type applies
+* its triggers, which specify the conditions in which policies of this type are fired
+
+Policy
+~~~~~~
+
+A Policy is used to specify the actual instances of policies that are used in a service. The parameter values of the
+policy and the actual entities to which it applies may be specified.
+
+The policies that are used in a service are defined in the policies section of the TOSCA topology template as a Policy.
+More formally, TOSCA defines a Policy as an artifact that "defines a policy that can be associated with a TOSCA
+topology or top-level entity definition". In the definition of a Policy in TOSCA, you specify:
+
+* its properties, which define the values of the configuration parameters that the policy takes
+* its targets, which define the node types and/or group types to which the policy type applies
+
+Note that policy triggers are specified on the Policy Type definition and are not specified on the Policy itself.
+
+Trigger
+~~~~~~~
+
+A Trigger defines an event, condition, and action that is used to initiate execution of a policy associated with it.
+The definition of the Trigger allows specification of the type of events to trigger on, the filters on those events,
+conditions and constraints for trigger firing, the action to perform on triggering, and various other parameters.
+
+The triggers that are used in a service are defined as reusable modules in the TOSCA service template as a Trigger.
+More formally, TOSCA defines a Trigger as an artifact that "defines the event, condition and action that is used to
+“trigger” a policy it is associated with". In the definition of a Trigger in TOSCA, you specify:
+
+* its event_type, which defines the name of the event that fires the policy
+* its schedule, which defines the time interval in which the trigger is active
+* its target_filter, which defines specific filters for firing such as specific characteristics of the nodes or
+relations for which the trigger should or should not fire
+* its condition, which defines extra conditions on the incoming event for firing the trigger
+* its constraint, which defines extra conditions on the incoming event for not firing the trigger
+* its period, which defines the period to use for evaluating conditions and constraints
+* its evaluations, which defines the number of evaluations that must be performed over the period to assert the
+condition or constraint exists
+* its method, the method to use for evaluation of conditions and constraints
+* its action, the workflow or operation to invoke when the trigger fires
+
+Note that how a Trigger actually works with a Policy is not clear from the specification.
+
+End of Document
+
