.. include:: ../../../router.1.0/srcDoc/vars.rst

.. _section-Arm:

Application Resource Model
**************************

|RTI_SERVICE|\s are described through a *hierarchical application resource
model*. In this model, an application is composed of a set of *Resources*, each
representing a particular component within the application. *Resources* have
a parent-child relationship. :numref:`FigureArmGeneralView` shows a general view
of this concept.

.. figure:: ../../../router.1.0/srcDoc/static/ArmGeneralView.svg
    :figwidth: 80 %
    :name: FigureArmGeneralView
    :align: center

    Application modeled as a set of related Resources

Each application specifies its resource model by indicating the available
resources and their relationship. A *Resource* is determined by its class and
a concrete object instance. It can belong to one of the following categories:

- **Simple**–Represents a single object.
- **Collection**–Represents a set of objects of the same class.

A Resource may be composed of one or more Resources. In this relationship,
the *parent* Resource is composed of one ore more *child* Resources.


.. _section-Arm-ExampleDds:

Example: Simple Resource Model of a |CONNEXT_HEADING| Application
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""

:numref:`FigureArmExampleDds` depicts a UML class diagram to provide a generic
resource model for |CONNEXT| applications.

.. figure:: ../../../router.1.0/srcDoc/static/ArmExampleDds.svg
    :figwidth: 85 %
    :name: FigureArmExampleDds
    :align: center

    Connext DDS application resource model

In this diagram, the composition relationship is used to denote the
parents and children in the hierarchy. The direct relationship
denotes a dependency between resources that is not parent-child.

.. _section-Arm-ResourceId:

Resource Identifiers
====================

A resource identifier is a string of characters that uniquely address a
concrete resource object within an application. It is expressed as a
hierarchical sequence of identifiers separated by  ``/``, including all the
parent resources and the target resource itself:

.. math::

    {/resource\_id_1/resource\_id_2} ... {/resource\_id_N}

where each individual identifier references a concrete resource object
*by its name*. The object name is either:

a) Fixed and specified by the resource model of the parent Resource class.
b) Given by the user of the application. This is the case where the parent
   resource is a collection in which the user can insert objects,
   providing a name for each of them.

The individual identifier can refer to one of the two kinds of resources,
simple and collection resources. For example:


.. list-table::
    :header-rows: 0

    * - /collection_id\ :sub:`1`\/resource_id\ :sub:`1`\/resource_id\ :sub:`2`\


If the identifier refers to a collection resource, the following
child identifier must refer to a simple resource. Both simple and collection
resources can be parents (or children). In the previous example,
resource_id\ :sub:`1`\  is a simple resource child of collection_id\ :sub:`1`\;
it is also the parent of resource_id\ :sub:`2`\.

The hierarchy of identifiers is known as the *full resource identifier path*,
where each resource on the left represents a parent resource. The *full resource
identifier path* is composed of collection and simple resources. Each child
resource identifier is known as the *relative resource* to the parent.

The resource identifier format follows these conventions:

- The first character is ``/``, which represents the root resource and parent
  of all the available resources across the applications.
- A collection identifier is defined in lower ``snake_case``, and it is always
  specified by the resource class.
- A simple resource identifier is defined in ``camelCase`` (lower and upper)
  and may be specified by both the resource class or the user.

Example: Resource Identifiers of a Generic |CONNEXT_HEADING| Application
""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""

Consider the |CONNEXT| application resource model in
:numref:`section-Arm-ExampleDds`. The following resource identifier addresses a
concrete |DP| named "MyParticipant" in a given application:

.. code-block:: html

    /domain_participants/MyParticipant

In this case, "domain_participants" is the identifier of a collection resource
that represents a set of |DPs| in the application and its value is fixed and
specified by the application. In contrast, "MyParticipant" is the identifier
of a simple resource that represents a particular |DP| and its value is given
by the user of the application at |DP| creation time.

The following resource identifier addresses the implicit |PUB| of a concrete
|DP| in a given application:

.. code-block:: html

    /domain_participants/MyParticipant/implicit_publisher

where "implicit_publisher" is the identifier of a simple resource that represents
the always-present implicit *Publisher* and its value is fixed and specified
by the |DP| resource class.