docs/apex/APEX-MyFirstPolicyExample.rst

.. This work is licensed under a Creative Commons Attribution 4.0 International License.
.. http://creativecommons.org/licenses/by/4.0

.. _apex-myFirstExample:

HowTo: My First Policy
**********************

.. contents::
    :depth: 3

Introduction
^^^^^^^^^^^^

      .. container:: sectionbody

          .. container:: paragraph

                  Consider a scenario where a supermarket chain called
                  *HyperM* controls how it sells items in a policy-based
                  manner. Each time an item is processed by *HyperM*'s
                  point-of-sale (PoS) system an event is generated and
                  published about that item of stock being sold. This
                  event can then be used to update stock levels, etc..

          .. container:: paragraph

                  *HyperM* want to extend this approach to allow some
                  checks to be performed before the sale can be
                  completed. This can be achieved by requesting a
                  policy-controlled decision as each item is processed
                  by for sale by each PoS system. The decision process
                  is integrated with *HyperM*'s other IT systems that
                  manage stock control, sourcing and purchasing,
                  personnel systems, etc.

          .. container:: paragraph

                  In this document we will show how APEX and APEX
                  Policies can be used to achieve this, starting with a
                  simple policy, building up to more complicated policy
                  that demonstrates the features of APEX.

Data Models
^^^^^^^^^^^

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               .. container:: sect2

                  .. rubric:: Sales Input Event
                     :name: sales_input_event

                  .. container:: paragraph

                     Each time a PoS system processes a sales item an
                     event with the following format is emitted:

                  .. table:: Table 1. Sale Input Event

                     +----------------------+----------------------+-----------------------+
                     | Event                | Fields               | Description           |
                     +======================+======================+=======================+
                     | SALE_INPUT           | time, sale_ID,       | Event indicating a    |
                     |                      | amount, item_ID,     | sale of an item is    |
                     |                      | quantity,            | occurring             |
                     |                      | assistant_ID,        |                       |
                     |                      | branch_ID, notes, …​ |                       |
                     +----------------------+----------------------+-----------------------+

                  .. container:: paragraph

                     In each ``SALE_INPUT`` event the ``sale_ID`` field
                     is a unique ID generated by the PoS system. A
                     timestamp for the event is stored in the ``time``
                     field. The ``amount`` field refers to the value of
                     the item(s) to be sold (in cents). The ``item_ID``
                     field is a unique identifier for each item type,
                     and can be used to retrieve more information about
                     the item from *HyperM*'s stock control system. The
                     ``quantity`` field refers to the quantity of the
                     item to be sold. The ``assistant_ID`` field is a
                     unique identifier for the PoS operator, and can be
                     used to retrieve more information about the
                     operator from the *HyperM*'s personnel system.
                     Since *HyperM* has many branches the ``branch_ID``
                     identifies the shop. The ``notes`` field contains
                     arbitrary notes about the sale.

               .. container:: sect2

                  .. rubric:: Sales Decision Event
                     :name: sales_decision_event

                  .. container:: paragraph

                     After a ``SALE_INPUT`` event is emitted by the PoS
                     system *HyperM*'s policy-based controlled sales
                     checking system emits a Sale Authorization Event
                     indicating whether the sale is authorized or
                     denied. The PoS system can then listen for this
                     event before continuing with the sale.

                  .. table:: Table 2. Sale Authorisation Event

                     +----------------------+----------------------+-----------------------+
                     | Event                | Fields               | Description           |
                     +======================+======================+=======================+
                     | SALE_AUTH            | sale_ID, time,       | Event indicating a    |
                     |                      | authorized, amount,  | sale of an item is    |
                     |                      | item_ID, quantity,   | authorized or denied  |
                     |                      | assistant_ID,        |                       |
                     |                      | branch_ID, notes,    |                       |
                     |                      | message…​            |                       |
                     +----------------------+----------------------+-----------------------+

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                     In each ``SALE_AUTH`` event the ``sale_ID`` field
                     is copied from the ``SALE_INPUT`` event that
                     trigger the decision request. The ``SALE_AUTH``
                     event is also timestamped using the ``time`` field,
                     and a field called ``authorised`` is set to
                     ``true`` or ``false`` depending on whether the sale
                     is authorized or denied. The ``message`` field
                     carries an optional message about why a sale was
                     not authorized. The other fields from the
                     ``SALE_INPUT`` event are also included for
                     completeness.

               .. container:: sect2

                  .. rubric:: Stock Control: Items
                     :name: stock_control_items

                  .. container:: paragraph

                     *HyperM* maintains information about each item for
                     sale in a database table called ``ITEMS``.

                  .. table:: Table 3. Items Database

                     +----------------------+----------------------+-----------------------+
                     | Table                | Fields               | Description           |
                     +======================+======================+=======================+
                     | ITEMS                | item_ID,             | Database table        |
                     |                      | description,         | describing each item  |
                     |                      | cost_price, barcode, | for sale              |
                     |                      | supplier_ID,         |                       |
                     |                      | category, …​         |                       |
                     +----------------------+----------------------+-----------------------+

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                     The database table ``ITEMS`` has a row for each
                     items that *HyperM* sells. Each item is identified
                     by an ``item_ID`` value. The ``description`` field
                     stores a description of the item. The cost price of
                     the item is given in ``cost_price``. The barcode of
                     the item is encoded in ``barcode``, while the item
                     supplier is identified by ``supplier_ID``. Items
                     may also be classified into categories using the
                     ``category`` field. Useful categories might
                     include: ``soft drinks``, ``alcoholic drinks``,
                     ``cigarettes``, ``knives``, ``confectionery``,
                     ``bakery``, ``fruit&vegetables``, ``meat``, etc..

               .. container:: sect2

                  .. rubric:: Personnel System: Assistants
                     :name: personnel_system_assistants

                  .. table:: Table 4. Assistants Database

                     +----------------------+----------------------+-----------------------+
                     | Table                | Fields               | Description           |
                     +======================+======================+=======================+
                     | ASSISTANTS           | assistant_ID,        | Database table        |
                     |                      | surname, firstname,  | describing each       |
                     |                      | middlename, age,     | *HyperM* sales        |
                     |                      | grade, phone_number, | assistant             |
                     |                      | …​                   |                       |
                     +----------------------+----------------------+-----------------------+

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                     The database table ``ASSISTANTS`` has a row for
                     each sales assistant employed by *HyperM*. Each
                     assistant is identified by an ``assistant_ID``
                     value, with their name given in the ``firstname``,
                     ``middlename`` and ``surname`` fields. The
                     assistant’s age in years is given in ``age``, while
                     their phone number is contained in the
                     ``phone_number`` field. The assistant’s grade is
                     encoded in ``grade``. Useful values for ``grade``
                     might include: ``trainee``, ``operator``,
                     ``supervisor``, etc..

               .. container:: sect2

                  .. rubric:: Locations: Branches
                     :name: locations_branches

                  .. table:: Table 5. Branches Database

                     +----------------------+----------------------+-----------------------+
                     | Table                | Fields               | Description           |
                     +======================+======================+=======================+
                     | BRANCHES             | branch_ID,           | Database table        |
                     |                      | branch_Name,         | describing each       |
                     |                      | category, street,    | *HyperM* branch       |
                     |                      | city, country,       |                       |
                     |                      | postcode, …​         |                       |
                     +----------------------+----------------------+-----------------------+

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                     *HyperM* operates a number of branches. Each branch
                     is described in the ``BRANCHES`` database table.
                     Each branch is identified by a ``branch_ID``, with
                     a branch name given in ``branch_Name``. The address
                     for the branch is encoded in ``street``, ``city``,
                     ``country`` and ``postcode``. The branch category
                     is given in the ``category`` field. Useful values
                     for ``category`` might include: ``Small``,
                     ``Large``, ``Super``, ``Hyper``, etc..


Policy Step 1
^^^^^^^^^^^^^

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               .. container:: sect1

                  .. rubric:: Scenario
                     :name: scenario

                  .. container:: paragraph

                     For the first version of our policy, let’s start
                     with something simple. Let us assume that there
                     exists some restriction that alcohol products
                     cannot be sold before 11:30am. In this section we
                     will go through the necessary steps to define a
                     policy that can enforce this for *HyperM*.

                  .. container:: ulist

                     -  Alcohol cannot be sold before 11:30am...

New Policy Model
----------------

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               .. container:: sect1

                  .. rubric:: Create the an new empty Policy Model ``MyFirstPolicyModel``
                     :name: create_the_an_new_empty_policy_model_code_myfirstpolicymodel_code

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                      Since an organisation like *HyperM* may have many
                      policies covering many different domains, policies should
                      be grouped into policy sets. In order to edit or deploy a
                      policy, or policy set, the definition of the policy(ies)
                      and all required events, tasks, states, etc., are grouped
                      together into a 'Policy Model'. An organization might
                      define many Policy Models, each containing a different
                      set of policies.

                  .. container:: paragraph

                      So the first step is to create a new empty Policy Model
                      called ``MyFirstPolicyModel``. Using the APEX Policy
                      Editor, click on the 'File' menus and select 'New'. Then
                      define our new policy model called
                      ``MyFirstPolicyModel``. Use the 'Generate UUID' button to
                      create a new unique ID for the policy model, and fill in
                      a description for the policy model. Press the ``Submit``
                      button to save your changes.

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                    .. container:: content

                      |File > New to create a new Policy Model|

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                    .. container:: content

                      |Create a new Policy Model|

Events
------

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          .. container:: sect1

            .. rubric:: Create the input event ``SALE_INPUT`` and the
               output event ``SALE_AUTH``
               :name: create_the_input_event_code_sale_input_code_and_the_output_event_code_sale_auth_code

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               Using the APEX Policy Editor, click on the 'Events' tab.
               In the 'Events' pane, right click and select 'New':

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                  |Right click to create a new event|

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               Create a new event type called ``SALE_INPUT``. Use the
               'Generate UUID' button to create a new unique ID for the
               event type, and fill in a description for the event. Add
               a namespace, e.g. ``com.hyperm``. We can add hard-coded
               strings for the ``Source`` and ``Target``, e.g. ``POS``
               and ``APEX``. At this stage we will not add any parameter
               fields, we will leave this until later. Use the
               ``Submit`` button to create the event.

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                  |Fill in the necessary information for the
                  'SALE_INPUT' event and click 'Submit'|

            .. container:: paragraph

               Repeat the same steps for a new event type called
               ``SALE_AUTH``. Just use ``APEX`` as source and ``POS`` as
               target, since this is the output event coming from APEX
               going to the sales point.

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               Before we can add parameter fields to an event we must
               first define APEX Context Item Schemas that can be used
               by those fields.

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               To create new item schemas, click on the 'Context Item
               Schemas' tab. In that 'Context Item Schemas' pane, right
               click and select 'Create new ContextSchema'.

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               .. container:: content

                  |Right click to create a new Item Schema|

            .. container:: paragraph

               Create item schemas with the following characteristics,
               each with its own unique UUID:

            .. table:: Table 1. Item Schemas

               +-----------------+-----------------+-----------------+-----------------+
               | Name            | Schema Flavour  | Schema          | Description     |
               |                 |                 | Definition      |                 |
               +=================+=================+=================+=================+
               | timestamp_type  | Java            | java.lang.Long  | A type for      |
               |                 |                 |                 | ``time`` values |
               +-----------------+-----------------+-----------------+-----------------+
               | sale_ID_type    | Java            | java.lang.Long  | A type for      |
               |                 |                 |                 | ``sale_ID``     |
               |                 |                 |                 | values          |
               +-----------------+-----------------+-----------------+-----------------+
               | price_type      | Java            | java.lang.Long  | A type for      |
               |                 |                 |                 | ``amo           |
               |                 |                 |                 | unt``/``price`` |
               |                 |                 |                 | values          |
               +-----------------+-----------------+-----------------+-----------------+
               | item_ID_type    | Java            | java.lang.Long  | A type for      |
               |                 |                 |                 | ``item_ID``     |
               |                 |                 |                 | values          |
               +-----------------+-----------------+-----------------+-----------------+
               | as              | Java            | java.lang.Long  | A type for      |
               | sistant_ID_type |                 |                 | `               |
               |                 |                 |                 | `assistant_ID`` |
               |                 |                 |                 | values          |
               +-----------------+-----------------+-----------------+-----------------+
               | quantity_type   | Java            | ja              | A type for      |
               |                 |                 | va.lang.Integer | ``quantity``    |
               |                 |                 |                 | values          |
               +-----------------+-----------------+-----------------+-----------------+
               | branch_ID_type  | Java            | java.lang.Long  | A type for      |
               |                 |                 |                 | ``branch_ID``   |
               |                 |                 |                 | values          |
               +-----------------+-----------------+-----------------+-----------------+
               | notes_type      | Java            | j               | A type for      |
               |                 |                 | ava.lang.String | ``notes``       |
               |                 |                 |                 | values          |
               +-----------------+-----------------+-----------------+-----------------+
               | authorised_type | Java            | ja              | A type for      |
               |                 |                 | va.lang.Boolean | ``authorised``  |
               |                 |                 |                 | values          |
               +-----------------+-----------------+-----------------+-----------------+
               | message_type    | Java            | j               | A type for      |
               |                 |                 | ava.lang.String | ``message``     |
               |                 |                 |                 | values          |
               +-----------------+-----------------+-----------------+-----------------+

            .. container:: imageblock

               .. container:: content

                  |Create a new Item Schema|

            .. container:: paragraph

               The item schemas can now be seen on the 'Context Item
               Schemas' tab, and can be updated at any time by
               right-clicking on the item schemas on the 'Context Item
               Schemas' tab. Now we can go back to the event definitions
               for ``SALE_INPUT`` and ``SALE_AUTH`` and add some
               parameter fields.

            .. TIP::

              .. container:: paragraph

                  APEX natively supports schema definitions in ``Java`` and ``Avro``.
                  ``Java`` schema definitions are simply the name of a Java Class. There are some restrictions:

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                  - the class must be instantiatable, i.e. not an Java interface or abstract class

                  - primitive types are not supported, i.e. use ``java.lang.Integer`` instead of ``int``, etc.

                  - it must be possible to find the class, i.e. the class must be contained in the Java classpath.

              .. container:: paragraph

                  ``Avro`` schema definitions can be any valid `Avro <https://avro.apac
                  he.org/docs/current/spec.html>`__ schema. For events using fields defined with
                  Avro schemas, any incoming event containing that field must contain a value that conforms to the Avro schema.

            .. container:: paragraph

               Click on the 'Events' tab, then right click the
               ``SALE_INPUT`` row and select 'Edit Event
               :literal:`SALE_INPUT’. To add a new event parameter use the 'Add Event Parameter' button at the bottom of the screen. For the `SALE_INPUT`
               event add the following event parameters:

            .. table:: Table 2. Event Parameter Fields for the ``SALE_INPUT`` Event

               +----------------------+----------------------+-----------------------+
               | Parameter Name       | Parameter Type       | Optional              |
               +======================+======================+=======================+
               | time                 | timestamp_type       | no                    |
               +----------------------+----------------------+-----------------------+
               | sale_ID              | sale_ID_type         | no                    |
               +----------------------+----------------------+-----------------------+
               | amount               | price_type           | no                    |
               +----------------------+----------------------+-----------------------+
               | item_ID              | item_ID_type         | no                    |
               +----------------------+----------------------+-----------------------+
               | quantity             | quantity_type        | no                    |
               +----------------------+----------------------+-----------------------+
               | assistant_ID         | assistant_ID_type    | no                    |
               +----------------------+----------------------+-----------------------+
               | branch_ID            | branch_ID_type       | no                    |
               +----------------------+----------------------+-----------------------+
               | notes                | notes_type           | *yes*                 |
               +----------------------+----------------------+-----------------------+

            .. container:: paragraph

               Remember to click the 'Submit' button at the bottom of
               the event definition pane.

            .. TIP::

              .. container:: paragraph

                  Parameter fields can be *optional* in events. If a parameter is not marked as
                  *optional* then by default it is *mandatory*, so it must appear in any input event
                  passed to APEX. If an *optional* field is not set for an output event then value
                  will be set to ``null``.

            .. container:: imageblock

               .. container:: content

                  |Add new event parameters to an event|

            .. container:: paragraph

               Select the ``SALE_AUTH`` event and add the following
               event parameters:

            .. table:: Table 3. Event Parameter Fields for the ``SALE_AUTH`` Event

               +----------------------+----------------------+-----------------------+
               | Parameter Name       | Parameter Type       | no                    |
               +======================+======================+=======================+
               | sale_ID              | sale_ID_type         | no                    |
               +----------------------+----------------------+-----------------------+
               | time                 | timestamp_type       | no                    |
               +----------------------+----------------------+-----------------------+
               | authorised           | authorised_type      | no                    |
               +----------------------+----------------------+-----------------------+
               | message              | message_type         | *yes*                 |
               +----------------------+----------------------+-----------------------+
               | amount               | price_type           | no                    |
               +----------------------+----------------------+-----------------------+
               | item_ID              | item_ID_type         | no                    |
               +----------------------+----------------------+-----------------------+
               | assistant_ID         | assistant_ID_type    | no                    |
               +----------------------+----------------------+-----------------------+
               | quantity             | quantity_type        | no                    |
               +----------------------+----------------------+-----------------------+
               | branch_ID            | branch_ID_type       | no                    |
               +----------------------+----------------------+-----------------------+
               | notes                | notes_type           | *yes*                 |
               +----------------------+----------------------+-----------------------+

            .. container:: paragraph

               Remember to click the 'Submit' button at the bottom of
               the event definition pane.

            .. container:: paragraph

               The events for our policy are now defined.

New Policy
----------

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          .. container:: sect1

            .. rubric:: Create a new Policy and add the *"No Booze
               before 11:30"* check
               :name: create_a_new_policy_and_add_the_em_no_booze_before_11_30_em_check

            .. container:: paragraph

               APEX policies are defined using a state-machine model.
               Each policy comprises one or more *states* that can be
               individually executed. Where there is more than one
               *state* the states are chained together to form a
               `Directed Acyclic Graph
               (DAG) <https://en.wikipedia.org/wiki/Directed_acyclic_graph>`__
               of states. A *state* is triggered by passing it a single
               input (or 'trigger') event and once executed each state
               then emits an output event. For each *state* the logic
               for the *state* is embedded in one or more *tasks*. Each
               *task* contains specific *task logic* that is executed by
               the APEX execution environment each time the *task* is
               invoked. Where there is more than one *task* in a *state*
               then the *state* also defines some *task selection logic*
               to select an appropriate task each time the *state* is
               executed.

            .. container:: paragraph

               Therefore, to create a new policy we must first define
               one or more tasks.

            .. container:: paragraph

               To create a new Task click on the 'Tasks' tab. In the
               'Tasks' pane, right click and select 'Create new Task'.
               Create a new Task called ``MorningBoozeCheck``. Use the
               'Generate UUID' button to create a new unique ID for the
               task, and fill in a description for the task.

            .. container:: imageblock

               .. container:: content

                  |Right click to create a new task|

            .. container:: paragraph

               Tasks are configured with a set of *input fields* and a
               set of *output fields*. To add new input/output fields
               for a task use the 'Add Task Input Field' and 'Add Task
               Output Field' button. The list of input and out fields to
               add for the ``MorningBoozeCheck`` task are given below.
               The input fields are drawn from the parameters in the
               state’s input event, and the task’s output fields are
               used to populate the state’s output event. The task’s
               input and output fields must be a subset of the event
               parameters defined for the input and output events for
               any state that uses that task. (You may have noticed that
               the input and output fields for the ``MorningBoozeCheck``
               task have the exact same names and reuse the item schemas
               that we used for the parameters in the ``SALE_INPUT`` and
               ``SALE_AUTH`` events respectively).

            .. table:: Table 1. Input fields for ``MorningBoozeCheck`` task

               +-----------------------------------+-----------------------------------+
               | Parameter Name                    | Parameter Type                    |
               +===================================+===================================+
               | time                              | timestamp_type                    |
               +-----------------------------------+-----------------------------------+
               | sale_ID                           | sale_ID_type                      |
               +-----------------------------------+-----------------------------------+
               | amount                            | price_type                        |
               +-----------------------------------+-----------------------------------+
               | item_ID                           | item_ID_type                      |
               +-----------------------------------+-----------------------------------+
               | quantity                          | quantity_type                     |
               +-----------------------------------+-----------------------------------+
               | assistant_ID                      | assistant_ID_type                 |
               +-----------------------------------+-----------------------------------+
               | branch_ID                         | branch_ID_type                    |
               +-----------------------------------+-----------------------------------+
               | notes                             | notes_type                        |
               +-----------------------------------+-----------------------------------+

            .. table:: Table 2. Output fields for ``MorningBoozeCheck`` task

               +-----------------------------------+-----------------------------------+
               | Parameter Name                    | Parameter Type                    |
               +===================================+===================================+
               | sale_ID                           | sale_ID_type                      |
               +-----------------------------------+-----------------------------------+
               | time                              | timestamp_type                    |
               +-----------------------------------+-----------------------------------+
               | authorised                        | authorised_type                   |
               +-----------------------------------+-----------------------------------+
               | message                           | message_type                      |
               +-----------------------------------+-----------------------------------+
               | amount                            | price_type                        |
               +-----------------------------------+-----------------------------------+
               | item_ID                           | item_ID_type                      |
               +-----------------------------------+-----------------------------------+
               | assistant_ID                      | assistant_ID_type                 |
               +-----------------------------------+-----------------------------------+
               | quantity                          | quantity_type                     |
               +-----------------------------------+-----------------------------------+
               | branch_ID                         | branch_ID_type                    |
               +-----------------------------------+-----------------------------------+
               | notes                             | notes_type                        |
               +-----------------------------------+-----------------------------------+

            .. container:: imageblock

               .. container:: content

                  |Add input and out fields for the task|

            .. container:: paragraph

               Each task must include some 'Task Logic' that implements
               the behaviour for the task. Task logic can be defined in
               a number of different ways using a choice of languages.
               For this task we will author the logic using the
               Java-like scripting language called
               ```MVEL`` <https://en.wikipedia.org/wiki/MVEL>`__.

            .. container:: paragraph

               For simplicity use the code for the task logic here(|taskLogicMvel_link|).
               Paste the script text into the 'Task Logic' box, and use
               "MVEL" as the 'Task Logic Type / Flavour'.

            .. container:: paragraph

               This logic assumes that all items with ``item_ID``
               between 1000 and 2000 contain alcohol, which is not very
               realistic, but we will see a better approach for this
               later. It also uses the standard ``Java`` time utilities
               to check if the current time is between ``00:00:00 GMT``
               and ``11:30:00 GMT``. For a detailed guide to how to
               write your own logic in
               ```JavaScript`` <https://en.wikipedia.org/wiki/JavaScript>`__,
               ```MVEL`` <https://en.wikipedia.org/wiki/MVEL>`__ or one
               of the other supported languages please refer to APEX
               Programmers Guide.


            .. container:: imageblock

               .. container:: content

                  |Add task logic the task|

            .. container:: paragraph

               An alternative version of the same logic is available in
               JavaScript(|taskLogicJS_link|). Just use "JAVASCRIPT" as the 'Task Logic Type
               / Flavour' instead.

            .. container:: paragraph

               The task definition is now complete so click the 'Submit'
               button to save the task. The task can now be seen on the
               'Tasks' tab, and can be updated at any time by
               right-clicking on the task on the 'Task' tab. Now that we
               have created our task, we can can create a policy that
               uses that task.

            .. container:: paragraph

               To create a new Policy click on the 'Policies' tab. In
               the 'Policies' pane, right click and select 'Create new
               Policy':

            .. container:: paragraph

               Create a new Policy called ``MyFirstPolicy``. Use the
               'Generate UUID' button to create a new unique ID for the
               policy, and fill in a description for the policy. Use
               'FREEFORM' as the 'Policy Flavour'.

            .. container:: paragraph

               Each policy must have at least one state. Since this is
               'freeform' policy we can add as many states as we wish.
               Let’s start with one state. Add a new state called
               ``BoozeAuthDecide`` to this ``MyFirstPolicy`` policy
               using the 'Add new State' button after filling in the
               name of our new state.

            .. container:: imageblock

               .. container:: content

                  |Create a new policy|

            .. container:: paragraph

               Each state must uses one input event type. For this new
               state select the ``SALE_INPUT`` event as the input event.

            .. container:: paragraph

               Each policy must define a 'First State' and a 'Policy
               Trigger Event'. The 'Policy Trigger Event' is the input
               event for the policy as a whole. This event is then
               passed to the first state in the chain of states in the
               policy, therefore the 'Policy Trigger Event' will be the
               input event for the first state. Each policy can only
               have one 'First State'. For our ``MyFirstPolicy`` policy,
               select ``BoozeAuthDecide`` as the 'First State'. This
               will automatically select ``SALE_INPUT`` as the 'Policy
               Trigger Event' for our policy.

            .. container:: imageblock

               .. container:: content

                  |Create a state|

            .. container:: paragraph

               In this case we will create a reference the pre-existing
               ``MorningBoozeCheck`` task that we defined above using
               the 'Add New Task' button. Select the
               ``MorningBoozeCheck`` task, and use the name of the task
               as the 'Local Name' for the task.

            .. container:: paragraph

               in the case where a state references more than one task,
               a 'Default Task' must be selected for the state and some
               logic ('Task Selection Logic') must be specified to
               select the appropriate task at execution time. Since our
               new state ``BoozeAuthDecide`` only has one task the
               default task is automatically selected and no 'Task
               Selection Logic' is required.

            .. NOTE::

              .. container:: paragraph

                  In a 'Policy' 'State' a 'State Output Mapping' has 3 roles: 1) Select which 'State'
                  should be executed next, 2) Select the type of the state’s 'Outgoing Event', and
                  3) Populate the state’s 'Outgoing Event'. This is how states are chained together
                  to form a (`Directed Acyclic Graph (DAG) <https://en.wikipedia.org/wiki/Directed_acyclic_graph>`__)
                  of states. The final state(s) of a policy are those that do not select any 'next'
                  state. Since a 'State' can only accept a single type of event, the type of the
                  event emitted by a previous 'State' must match the incoming event type of the next
                  'State'. This is also how the last state(s) in a policy can emit events of
                  different types. The 'State Output Mapping' is also responsible for taking the
                  fields that are output by the task executed in the state and populating the
                  state’s output populating the state’s output event before it is emitted.

                  Each 'Task' referenced in 'State' must have a defined 'Output Mapping' to take the output of the task, select an 'Outgoing Event' type for the state, populate the state's outgoing event, and then select the next state to be executed (if any).

                  There are 2 basic types of output mappings:

              .. container:: olist arabic

                  #. **Direct Output Mappings** have a single value for 'Next State' and a single value for 'State Output Event'. The outgoing event for the state is automatically created, any outgoing event parameters that were present in the incoming event are copied into the outgoing event, then any task output fields that have the same name and type as parameters in the outgoing event are automatically copied into the outgoing event.
                  #. **Logic-Based State Output Mappings / Finalizers** have some logic defined that dynamically selects and creates the 'State Outgoing Event', manages the population of the outgoing event parameters (perhaps changing or adding to the outputs from the task), and then dynamically selects the next state to be executed (if any).

            .. container:: paragraph

               Each task reference must also have an associated 'Output
               State Mapping' so we need an 'Output State Mapping' for
               the ``BoozeAuthDecide`` state to use when the
               ``MorningBoozeCheck`` task is executed. The simplest type
               of output mapping is a 'Direct Output Mapping'.

            .. container:: paragraph

               Create a new 'Direct Output Mapping' for the state called
               ``MorningBoozeCheck_Output_Direct`` using the 'Add New
               Direct State Output Mapping' button. Select ``SALE_AUTH``
               as the output event and select ``None`` for the next
               state value. We can then select this output mapping for
               use when the the ``MorningBoozeCheck`` task is executed.
               Since there is only state, and only one task for that
               state, this output mapping ensures that the
               ``BoozeAuthDecide`` state is the only state executed and
               the state (and the policy) can only emit events of type
               ``SALE_AUTH``. (You may remember that the output fields
               for the ``MorningBoozeCheck`` task have the exact same
               names and reuse the item schemas that we used for the
               parameters in ``SALE_AUTH`` event. The
               ``MorningBoozeCheck_Output_Direct`` direct output mapping
               can now automatically copy the values from the
               ``MorningBoozeCheck`` task directly into outgoing
               ``SALE_AUTH`` events.)

            .. container:: imageblock

               .. container:: content

                  |Add a Task and Output Mapping|

            .. container:: paragraph

               Click the 'Submit' button to complete the definition of
               our ``MyFirstPolicy`` policy. The policy
               ``MyFirstPolicy`` can now be seen in the list of policies
               on the 'Policies' tab, and can be updated at any time by
               right-clicking on the policy on the 'Policies' tab.

            .. container:: paragraph

               The ``MyFirstPolicyModel``, including our
               ``MyFirstPolicy`` policy can now be checked for errors.
               Click on the 'Model' menu and select 'Validate'. The
               model should validate without any 'Warning' or 'Error'
               messages. If you see any 'Error' or 'Warning' messages,
               carefully read the message as a hint to find where you
               might have made a mistake when defining some aspect of
               your policy model.

            .. container:: imageblock

               .. container:: content

                  |Validate the policy model for error using the 'Model'
                  > 'Validate' menu item|

            .. container:: paragraph

               Congratulations, you have now completed your first APEX
               policy. The policy model containing our new policy can
               now be exported from the editor and saved. Click on the
               'File' menu and select 'Download' to save the policy
               model in JSON format. The exported policy model is then
               available in the directory you selected, for instance
               ``$APEX_HOME/examples/models/MyFirstPolicy/1/MyFirstPolicyModel_0.0.1.json``.
               The exported policy can now be loaded into the APEX
               Policy Engine, or can be re-loaded and edited by the APEX
               Policy Editor.

            .. container:: imageblock

               .. container:: content

                  |Download the completed policy model using the 'File'
                  > 'Download' menu item|

Test The Policy
---------------

      .. container:: sectionbody

          .. container:: sect1

            .. rubric:: Test Policy Step 1
               :name: test_policy_step_1

            .. container:: paragraph

               To start a new APEX Engine you can use the following
               |policy1_configuration|. In a full APEX installation you can find
               this configuration in
               ``$APEX_HOME/examples/config/MyFirstPolicy/1/MyFirstPolicyConfigStdin2StdoutJsonEvent.json``.
               This configuration expects incoming events to be in
               ``JSON`` format and to be passed into the APEX Engine
               from ``stdin``, and result events will be printed in
               ``JSON`` format to ``stdout``. This configuration loads
               the policy model stored in the file
               'MyFirstPolicyModel_0.0.1.json' as exported from the APEX
               Editor. Note, you may need to edit this file to provide
               the full path to wherever you stored the exported policy
               model file.

            .. container:: paragraph

               To test the policy try paste the following events into
               the console as the APEX engine executes:

            .. list-table:: Title
              :widths: 25 40 35
              :header-rows: 1

              * - Input Event (JSON)
                - Output Event (JSON)
                - comment
              * - .. literalinclude:: events/1/EventIn_NonBoozeItem_101309GMT.json
                    :language: JSON
                - .. literalinclude:: events/1/EventOut_NonBoozeItem_101309GMT.json
                    :language: JSON
                - .. container:: paragraph

                    Request to buy a non-alcoholic item (item_ID=5123) at 10:13:09 on Tuesday, 10 January 2017.
                    Sale is authorized.
              * - .. literalinclude:: events/1/EventIn_BoozeItem_084106GMT.json
                    :language: JSON
                - .. literalinclude:: events/1/EventOut_BoozeItem_084106GMT.json
                    :language: JSON
                - .. container:: paragraph

                    Request to buy alcohol item (`item_ID=1249`) at 08:41:06 on Monday, 02 January 2017.
                    Sale is not authorized.
              * - .. literalinclude:: events/1/EventIn_BoozeItem_201713GMT.json
                    :language: JSON
                - .. literalinclude:: events/1/EventOut_BoozeItem_201713GMT.json
                    :language: JSON
                - .. container:: paragraph

                    Request to buy alcohol (`item_ID=1943`) at 20:17:13 on Tuesday, 20 December 2016.
                    Sale is authorized.


CLI Editor File
---------------

      .. container:: sectionbody

          .. container:: sect1

            .. rubric:: Policy 1 in CLI Editor
               :name: policy_1_in_cli_editor

            .. container:: paragraph

               An equivalent version of the ``MyFirstPolicyModel``
               policy model can again be generated using the APEX CLI
               editor. A sample APEX CLI script is shown below:

               .. container:: ulist

                     -  |policy1ModelMvel_link|
                     -  |policy1ModelJs_link|


Policy Step 2
^^^^^^^^^^^^^

      .. container:: sectionbody

               .. container:: sect1

                  .. rubric:: Scenario
                     :name: scenario_policy2

                  .. container:: paragraph

                     *HyperM* have just opened a new branch in a
                     different country, but that country has different
                     rules about when alcohol can be sold! In this
                     section we will go through the necessary steps to
                     extend our policy to enforce this for *HyperM*.

                  .. container:: ulist

                     -  In some branches alcohol cannot be sold before
                        1pm, and not at all on Sundays.

                  .. container:: paragraph

                     Although there are a number of ways to accomplish
                     this the easiest approach for us is to define
                     another task and then select which task is
                     appropriate at runtime depending on the branch
                     identifier in the incoming event.

Extend Policy Model
-------------------

      .. container:: sectionbody

         .. container:: sect2

            .. rubric:: Extend the Policy with the new Scenario
               :name: extend_the_policy_with_the_new_scenario

            .. container:: paragraph

               To create a new Task click on the 'Tasks' tab. In the
               'Tasks' pane, right click and select 'Create new Task':

            .. container:: paragraph

               Create a new Task called ``MorningBoozeCheckAlt1``. Use
               the 'Generate UUID' button to create a new unique ID for
               the task, and fill in a description for the task. Select
               the same input and output fields that we used earlier
               when we defined the ``MorningBoozeCheck`` task earlier.

            .. table:: Table 1. Input fields for ``MorningBoozeCheckAlt1`` task

               +-----------------------------------+-----------------------------------+
               | Parameter Name                    | Parameter Type                    |
               +===================================+===================================+
               | time                              | timestamp_type                    |
               +-----------------------------------+-----------------------------------+
               | sale_ID                           | sale_ID_type                      |
               +-----------------------------------+-----------------------------------+
               | amount                            | price_type                        |
               +-----------------------------------+-----------------------------------+
               | item_ID                           | item_ID_type                      |
               +-----------------------------------+-----------------------------------+
               | quantity                          | quantity_type                     |
               +-----------------------------------+-----------------------------------+
               | assistant_ID                      | assistant_ID_type                 |
               +-----------------------------------+-----------------------------------+
               | branch_ID                         | branch_ID_type                    |
               +-----------------------------------+-----------------------------------+
               | notes                             | notes_type                        |
               +-----------------------------------+-----------------------------------+

            .. table:: Table 2. Output fields for ``MorningBoozeCheckAlt1`` task

               +-----------------------------------+-----------------------------------+
               | Parameter Name                    | Parameter Type                    |
               +===================================+===================================+
               | sale_ID                           | sale_ID_type                      |
               +-----------------------------------+-----------------------------------+
               | time                              | timestamp_type                    |
               +-----------------------------------+-----------------------------------+
               | authorised                        | authorised_type                   |
               +-----------------------------------+-----------------------------------+
               | message                           | message_type                      |
               +-----------------------------------+-----------------------------------+
               | amount                            | price_type                        |
               +-----------------------------------+-----------------------------------+
               | item_ID                           | item_ID_type                      |
               +-----------------------------------+-----------------------------------+
               | assistant_ID                      | assistant_ID_type                 |
               +-----------------------------------+-----------------------------------+
               | quantity                          | quantity_type                     |
               +-----------------------------------+-----------------------------------+
               | branch_ID                         | branch_ID_type                    |
               +-----------------------------------+-----------------------------------+
               | notes                             | notes_type                        |
               +-----------------------------------+-----------------------------------+

            .. container:: paragraph

               This task also requires some 'Task Logic' to implement
               the new behaviour for this task.

            .. container:: paragraph

               For simplicity use the following code for the task logic (|policy2_taskLogic_link|).
               It again assumes that all items with ``item_ID`` between
               1000 and 2000 contain alcohol. We again use the standard
               ``Java`` time utilities to check if the current time is
               between ``00:00:00 CET`` and ``13:00:00 CET`` or if it is
               ``Sunday``.

            .. container:: paragraph

               For this task we will again author the logic using the
               ```MVEL`` <https://en.wikipedia.org/wiki/MVEL>`__
               scripting language. Sample task logic code (specified in
               ```MVEL`` <https://en.wikipedia.org/wiki/MVEL>`__) is
               given below. For a detailed guide to how to write your
               own logic in
               ```JavaScript`` <https://en.wikipedia.org/wiki/JavaScript>`__,
               ```MVEL`` <https://en.wikipedia.org/wiki/MVEL>`__ or one
               of the other supported languages please refer to APEX
               Programmers Guide.

              .. container:: imageblock

                .. container:: content

                  |Create a new alternative task
                  \`MorningBoozeCheckAlt1\`|

            .. container:: paragraph

               The task definition is now complete so click the 'Submit'
               button to save the task. Now that we have created our
               task, we can can add this task to the single pre-existing
               state (``BoozeAuthDecide``) in our policy.

            .. container:: paragraph

               To edit the ``BoozeAuthDecide`` state in our policy click
               on the 'Policies' tab. In the 'Policies' pane, right
               click on our ``MyFirstPolicy`` policy and select 'Edit'.
               Navigate to the ``BoozeAuthDecide`` state in the 'states'
               section at the bottom of the policy definition pane.

              .. container:: imageblock

               .. container:: content

                  |Right click to edit a policy|

            .. container:: paragraph

               To add our new task ``MorningBoozeCheckAlt1``, scroll
               down to the ``BoozeAuthDecide`` state in the 'States'
               section. In the 'State Tasks' section for
               ``BoozeAuthDecide`` use the 'Add new task' button. Select
               our new ``MorningBoozeCheckAlt1`` task, and use the name
               of the task as the 'Local Name' for the task. The
               ``MorningBoozeCheckAlt1`` task can reuse the same
               ``MorningBoozeCheck_Output_Direct`` 'Direct State Output
               Mapping' that we used for the ``MorningBoozeCheck`` task.
               (Recall that the role of the 'State Output Mapping' is to
               select the output event for the state, and select the
               next state to be executed. These both remain the same as
               before.)

            .. container:: paragraph

               Since our state has more than one task we must define
               some logic to determine which task should be used each
               time the state is executed. This *task selection logic*
               is defined in the state definition. For our
               ``BoozeAuthDecide`` state we want the choice of which
               task to use to be based on the ``branch_ID`` from which
               the ``SALE_INPUT`` event originated. For simplicity sake
               let us assume that branches with ``branch_ID`` between
               ``0`` and ``999`` should use the ``MorningBoozeCheck``
               task, and the branches with with ``branch_ID`` between
               ``1000`` and ``1999`` should use the
               ``MorningBoozeCheckAlt1`` task.

            .. container:: paragraph

               This time, for variety, we will author the task selection
               logic using the
               ```JavaScript`` <https://en.wikipedia.org/wiki/JavaScript>`__
               scripting language. Sample task selection logic code
               is given here (|policy2_taskSelectionLogic_link|). Paste the script text into the 'Task
               Selection Logic' box, and use "JAVASCRIPT" as the 'Task
               Selection Logic Type / Flavour'. It is necessary to mark
               one of the tasks as the 'Default Task' so that the task
               selection logic always has a fallback default option in
               cases where a particular task cannot be selected. In this
               case the ``MorningBoozeCheck`` task can be the default
               task.


              .. container:: imageblock

               .. container:: content

                  |State definition with 2 Tasks and Task Selection
                  Logic|

            .. container:: paragraph

               When complete don’t forget to click the 'Submit' button
               at the bottom of 'Policies' pane for our
               ``MyFirstPolicy`` policy after updating the
               ``BoozeAuthDecide`` state.

            .. container:: paragraph

               Congratulations, you have now completed the second step
               towards your first APEX policy. The policy model
               containing our new policy can again be validated and
               exported from the editor and saved as shown in Step 1.

            .. container:: paragraph

               The exported policy model is then available in the
               directory you selected, as **MyFirstPolicyModel_0.0.1.json**.
               The exported policy can now be loaded into the APEX
               Policy Engine, or can be re-loaded and edited by the APEX
               Policy Editor.

Test The Policy
---------------

      .. container:: sectionbody

         .. container:: sect2

            .. rubric:: Test Policy Step 2
               :name: test_policy_step_2

            .. container:: paragraph

               To start a new APEX Engine you can use the following
               |policy2_configuration_link|. In a full APEX installation you can find
               this configuration in
               ``$APEX_HOME/examples/config/MyFirstPolicy/2/MyFirstPolicyConfigStdin2StdoutJsonEvent.json``.
               Note, this has changed from the configuration file in
               Step 1 to enable the ``JAVASCRIPT`` executor for our new
               'Task Selection Logic'.

            .. container:: paragraph

               To test the policy try paste the following events into
               the console as the APEX engine executes. Note, all tests
               from Step 1 will still work perfectly since none of those
               events originate from a branch with ``branch_ID`` between
               ``1000`` and ``2000``. The 'Task Selection Logic' will
               therefore pick the ``MorningBoozeCheck`` task as
               expected, and will therefore give the same results.

            .. list-table:: Table 1. Inputs and Outputs when testing *My First Policy*
              :widths: 25 40 35
              :header-rows: 1

              * - Input Event (JSON)
                - Output Event (JSON)
                - comment
              * - .. literalinclude:: events/1/EventIn_BoozeItem_084106GMT.json
                    :language: JSON
                - .. literalinclude:: events/1/EventOut_BoozeItem_084106GMT.json
                    :language: JSON
                - .. container:: paragraph

                    Request to buy alcohol item (`item_ID=1249`) at 08:41:06 GMT on Monday, 02 January 2017.
                    Sale is not authorized. Uses the `MorningBoozeCheck` task.

              * - .. literalinclude:: events/2/EventIn_BoozeItem_101433CET_thurs.json
                    :language: JSON
                - .. literalinclude:: events/2/EventOut_BoozeItem_101433CET_thurs.json
                    :language: JSON
                - .. container:: paragraph

                    Request to buy alcohol (`item_ID=1047`) at 10:14:33 on Thursday, 22 December 2016.
                    Sale is not authorized. Uses the `MorningBoozeCheckAlt1` task.

              * - .. literalinclude:: events/2/EventIn_BoozeItem_171937CET_sun.json
                    :language: JSON
                - .. literalinclude:: events/2/EventOut_BoozeItem_171937CET_sun.json
                    :language: JSON
                - .. container:: paragraph

                    Request to buy alcohol (`item_ID=1443`) at 17:19:37 on Sunday, 18 December 2016.
                    Sale is not authorized. Uses the `MorningBoozeCheckAlt1` task.

              * - .. literalinclude:: events/2/EventIn_NonBoozeItem_111309CET_mon.json
                    :language: JSON
                - .. literalinclude:: events/2/EventOut_NonBoozeItem_111309CET_mon.json
                    :language: JSON
                - .. container:: paragraph

                    Request to buy non-alcoholic item (`item_ID=5321`) at 11:13:09 on Monday, 2 January 2017.
                    Sale is authorized. Uses the `MorningBoozeCheckAlt1` task.

CLI Editor File
---------------

      .. container:: sectionbody

         .. container:: sect2

            .. rubric:: Policy 2 in CLI Editor
               :name: policy_2_in_cli_editor

            .. container:: paragraph

               An equivalent version of the ``MyFirstPolicyModel``
               policy model can again be generated using the APEX CLI
               editor. A sample APEX CLI script is shown below:

              .. container:: ulist

                     -  |policy2_Model_link|


   .. container::
      :name: footer-text

      2.3.0-SNAPSHOT
      Last updated 2020-04-03 16:04:24 IST

.. |File > New to create a new Policy Model| image:: images/mfp/MyFirstPolicy_P1_newPolicyModel1.png
.. |Create a new Policy Model| image:: images/mfp/MyFirstPolicy_P1_newPolicyModel2.png
.. |Right click to create a new event| image:: images/mfp/MyFirstPolicy_P1_newEvent1.png
.. |Fill in the necessary information for the 'SALE_INPUT' event and click 'Submit'| image:: images/mfp/MyFirstPolicy_P1_newEvent2.png
.. |Right click to create a new Item Schema| image:: images/mfp/MyFirstPolicy_P1_newItemSchema1.png
.. |Create a new Item Schema| image:: images/mfp/MyFirstPolicy_P1_newItemSchema2.png
.. |Add new event parameters to an event| image:: images/mfp/MyFirstPolicy_P1_newEvent3.png
.. |Right click to create a new task| image:: images/mfp/MyFirstPolicy_P1_newTask1.png
.. |Add input and out fields for the task| image:: images/mfp/MyFirstPolicy_P1_newTask2.png
.. |Add task logic the task| image:: images/mfp/MyFirstPolicy_P1_newTask3.png
.. |Create a new policy| image:: images/mfp/MyFirstPolicy_P1_newPolicy1.png
.. |Create a state| image:: images/mfp/MyFirstPolicy_P1_newState1.png
.. |Add a Task and Output Mapping| image:: images/mfp/MyFirstPolicy_P1_newState2.png
.. |Validate the policy model for error using the 'Model' > 'Validate' menu item| image:: images/mfp/MyFirstPolicy_P1_validatePolicyModel.png
.. |Download the completed policy model using the 'File' > 'Download' menu item| image:: images/mfp/MyFirstPolicy_P1_exportPolicyModel1.png
.. |Create a new alternative task `MorningBoozeCheckAlt1`| image:: images/mfp/MyFirstPolicy_P2_newTask1.png
.. |Right click to edit a policy| image:: images/mfp/MyFirstPolicy_P2_editPolicy1.png
.. |State definition with 2 Tasks and Task Selection Logic| image:: images/mfp/MyFirstPolicy_P2_editState1.png
.. |taskLogicMvel_link| raw:: html

  <a href="https://github.com/onap/policy-apex-pdp/tree/master/examples/examples-myfirstpolicy/src/main/resources/examples/models/MyFirstPolicy/1/MorningBoozeCheck.mvel" target="_blank">Task Logic: MorningBoozeCheck.mvel</a>
.. |taskLogicJs_link| raw:: html

  <a href="https://github.com/onap/policy-apex-pdp/tree/master/examples/examples-myfirstpolicy/src/main/resources/examples/models/MyFirstPolicy/1/MorningBoozeCheck.js" target="_blank">Task Logic: MorningBoozeCheck.js</a>
.. |policy1_configuration| raw:: html

  <a href="https://github.com/onap/policy-apex-pdp/tree/master/examples/examples-myfirstpolicy/src/main/resources/examples/config/MyFirstPolicy/1/MyFirstPolicyConfigStdin2StdoutJsonEvent.json" target="_blank">configuration</a>
.. |policy1ModelMvel_link| raw:: html

  <a href="https://github.com/onap/policy-apex-pdp/tree/master/examples/examples-myfirstpolicy/src/main/resources/examples/models/MyFirstPolicy/1/MyFirstPolicyModelMvel_0.0.1.apex" target="_blank">APEX CLI Editor code for Policy 1 using .Mvel Task Logic</a>
.. |policy1ModelJs_link| raw:: html

  <a href="https://github.com/onap/policy-apex-pdp/tree/master/examples/examples-myfirstpolicy/src/main/resources/examples/models/MyFirstPolicy/1/MyFirstPolicyModelJavascript_0.0.1.apex" target="_blank">APEX CLI Editor code for Policy 1 using .Js Task Logic</a>
.. |policy2_taskLogic_link| raw:: html

  <a href="https://github.com/onap/policy-apex-pdp/tree/master/examples/examples-myfirstpolicy/src/main/resources/examples/models/MyFirstPolicy/2/MorningBoozeCheckAlt1.mvel" target="_blank">`MorningBoozeCheckAlt1` task logic (`MVEL`)</a>
.. |policy2_taskSelectionLogic_link| raw:: html

  <a href="https://github.com/onap/policy-apex-pdp/tree/master/examples/examples-myfirstpolicy/src/main/resources/examples/models/MyFirstPolicy/2/MyFirstPolicy_BoozeAuthDecideTSL.js" target="_blank">`BoozeAuthDecide` task selection logic (`JavaScript`)</a>
.. |policy2_configuration_link| raw:: html

  <a href="https://github.com/onap/policy-apex-pdp/tree/master/examples/examples-myfirstpolicy/src/main/resources/examples/config/MyFirstPolicy/2/MyFirstPolicyConfigStdin2StdoutJsonEvent.json" target="_blank">configuration</a>
.. |policy2_Model_link| raw:: html

  <a href="https://github.com/onap/policy-apex-pdp/tree/master/examples/examples-myfirstpolicy/src/main/resources/examples/models/MyFirstPolicy/2/MyFirstPolicyModel_0.0.1.apex" target="_blank">APEX CLI Editor code for Policy 2</a>