Application descriptor reference
================================

Purpose
-------

The Application descriptor file is an XML document that describes an Application workflow (see :doc:`Application workflow </design/workflow>`). With it you can define in a structured way, the steps needed by your application to:

* provide a service interface (based on the OGC WPS standard);
* discover and download input data;
* process data, producing intermediate and final results;
* trigger remote web processing services;
* publish result files.

Descriptor type
---------------

The application descriptor is an XML file available in $_CIOP_APPLICATION_PATH/application.xml 

.. note:: the value $_CIOP_APPLICATION_PATH is /application

Descriptor structure
--------------------

The application descriptor structure consists of two separate sections:

#. jobTemplates
#. workflow

The **first part** defines the job templates that are then instantiated as workflow steps of the Directed Acyclic Graph.

Each job template contains:

* the path to the streaming executable
* parameters and optionally their allowed and default values
* properties (e.g. maximum number of tasks, processing timeout, etc.)

The **second part** contains the workflow steps, here called "nodes".

Each node can contain:

* the source for the inputs (e.g. a previous node, a catalogue series, a local file or a list of values)  
* their parameter values to override the default parameters (defined in the job template above)