Explain how to add a new Specification

CHANGELOG.md

@@ -5,6 +5,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 
 ## [Unreleased]
 ### Added
+- Execution of the workflow created thanks to the diagram editor ([#37](https://github.com/KazeJiyu/ekumi/pull/37))
+- User documentation ([#36](https://github.com/KazeJiyu/ekumi/pull/36))
 - Customization of new Workflow projects ([#34](https://github.com/KazeJiyu/ekumi/pull/34))
 - Simple workflow diagram editor ([#26](https://github.com/KazeJiyu/ekumi/pull/26))
 - Launch configurations for Activity ([#20](https://github.com/KazeJiyu/ekumi/pull/20))

docs/extend-ekumi/add-specification.rst

@@ -0,0 +1,56 @@
+Add a new Specification
+#############################
+
+.. important:: This section requires some knowledge about `Eclipse Extension Points <https://www.vogella.com/tutorials/EclipseExtensionPoint/article.html>`_.
+
+What is a specification?
+------------------------------
+
+A specification describes a possible representation of a workflow. The main purposes of specifications is allowing new workflow editors.
+
+How to add a new specification?
+-------------------------------------
+
+A new one can be defined by contributing to the ``fr.kazejiyu.ekumi.model.specs`` extension point.
+
+It requires one class that implements the ``ActivityAdapter`` interface.
+
+The interface is defined as follows:
+
+.. code-block:: java
+   :linenos:
+
+     public interface ActivityAdapter {
+
+        /**
+         * Returns whether the adapter can turn the given specification into an Activity.
+         *
+         * @param specification
+         * 			The specification to adapt, may be null.
+         *
+         * @return whether the adapter can turn the given specification into an Activity
+         */
+         boolean canAdapt(Object specification);
+
+        /**
+         * Creates an Activity from the given specification.
+         *
+         * @param specification
+         * 			The specification to adapt.
+         * @param datatypes
+         * 			The factory used to instantiate available datatypes.
+         * @param languages
+         * 			The factory used to instantiate available scripting languages.
+         *
+         * @return a new Activity
+         */
+         Optional<Activity> adapt(Object specification, DataTypeFactory datatypes, ScriptingLanguageFactory languages);
+
+      }
+
+An ``ActivityAdapter`` is responsible of turning your own specification model into an ``Activity`` so that the framework can execute it.
+
+How to integrate the new specification within the IDE?
+------------------------------------------------------------------------------------
+
+.. important:: Feature not implemented yet.

docs/index.rst

@@ -36,7 +36,8 @@ The behaviour of a task is defined by writting a `runner` using one of the suppo
 
 .. toctree::
    :maxdepth: 2
-   :caption: Extensibility
+   :caption: Extend EKumi
 
-   extensibility/add_scripting_language
-   extensibility/add_data_type
+   extend-ekumi/add_scripting_language
+   extend-ekumi/add_data_type
+   extend-ekumi/add-specification