.. _architecture:

Architecture
============

An EDG installation that has been extended with ``EDG-AF`` consists of:

1. The EDG server running in Tomcat or another servlet container
2. One or more ``EDG-AF`` apps running outside the EDG server
3. The EDG App Framework: code that connects ``EDG-AF`` apps with the EDG server

The design is inspired by `Shopify apps <https://shopify.dev/concepts/apps>`_.

**1. EDG server**

The EDG server is deployed in the `usual way <https://doc.topquadrant.com/7.0/administrator-guide/>`_, as a Java web application (.war) in a servlet container such as Tomcat. 
EDG-AF does not require any special configuration of the EDG server.

EDG-AF apps manipulate the EDG server programmatically via the latter's public APIs.
These are enabled by default, but the means of accessing them differs depending on the authentication system. 
See the `EDG developer documentation documentation <https://doc.topquadrant.com/7.0/integrating-external-systems-with-edg/>`_ and the EDG client documentation for information on programmatic access to the EDG APIs.

**2. EDG-AF Apps**

An ``EDG-AF`` app is a web application that answers HTTP requests on certain paths. Only one path is required of all applications:

    GET /configuration

which returns a JSON object describing the features an ``EDG-AF`` app supports (e.g., importers, jobs). See the :ref:`api` reference for the expected shape of this object.

Depending on the configuration, additional paths may be requested. For example, if ``GET /configuration`` returns an importer configuration with ``"id": "example"``, then::

    GET /importer/example

should serve an HTML page with form inputs for the importer.

**3. The EDG App Framework**

EDG-AF apps are installed into an EDG Ecosystem by:

#. Requesting ``/configuration`` to find out the features an ``EDG-AF`` app supports
#. Generating an EDG project (.zip file) that connects to the ``EDG-AF`` app from EDG
#. Uploading the EDG project to EDG

The EDG project generated during the installation process makes use of integration points provided by the EDG core product for the ``EDG-AF`` app.
For example, when an ``EDG-AF`` app includes an importer the installation process will generate RDF that defines an ``ImportPlugin`` as well as an SWP page for the importer. 
The SWP page will contain an embedded ``<iframe>`` that connects to the ``EDG-AF`` web application.