This document covers the **release 12.07** of the NodeSoftware.

Links to HTML-versions:

* Last release: http://readthedocs.org/docs/vamdc-nodesoftware/en/release/
* Latest development: http://readthedocs.org/docs/vamdc-nodesoftware/en/latest/

Links to PDF-versions:

* Last release: http://media.readthedocs.org/pdf/vamdc-nodesoftware/release/vamdc-nodesoftware.pdf 
* Latest development: http://media.readthedocs.org/pdf/vamdc-nodesoftware/latest/vamdc-nodesoftware.pdf


.. _intro:

Introduction
=============

About VAMDC
-------------

The Virtual Atomic and Molecular Data Center is a EU FP7 research 
infrastructure project and you can read all about it on http://vamdc.eu/


VAMDC nodes
-------------

A "node" within VAMDC is a data service that offers its data using the
standards and protocols defined by the VAMDC. They are web services with a
simple API, the specification of which can be found in the documentation for
the VAMDC standards: http://vamdc.org/documents/standards/ 

The scope of this document is to serve as documentation for the 
reference implementation of such a service. The goal of this 
implementation is to serve as publishing tools for new data services, 
i.e. it is meant to be easily deployed at multiple nodes.


A versatile implementation of VAMDC standards
---------------------------------------------

Principle design decisions that were made to arrive at
this software package include

* *Open source*. No software licences need to be bought and the used 
  software can be adapted if needed.
* The data must exist in a *relational database*. If this is not the
  case yet, a tool for creating it is provided. 
* *Flexibility in the data structure*.
  The service should be able to be plugged on top of existing databases
  and therefore needs to cope with almost arbitrary internal data formats.
* *Re-usable code*. The implementation of the VAMDC standards and protocols
  themselves should not depend on the requirements of a specific node.

Since the last two points contradict each other in practice, there needs 
to be an intermediate layer of abstraction that hides the node-specific 
details like the database layout from the parts of code that are shared 
between nodes.

Our implementation of the VAMDC node software is therefore based on a 
framework called `Django <http://www.djangoproject.com/>`_ (which in 
turn is based on the programming language `Python 
<http://www.python.org>`_) that provides both the database abstraction 
layer and high level tools for implementing web services.

The ingredients for a VAMDC node based on this software package and its 
operation look schematically like this:

.. image:: nodelayout.png
   :width: 700 px
   :alt: Structural layout of a VAMDC node