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

*Python AVM Library* is a library for working with `Astronomy Visualization Metadata <http://www.virtualastronomy.org>`_ in the XMP format.


Python AVM Library has been developed by:

 * `ESA/Hubble - European Space Agency <http://www.spacetelescope.org>`_ 
 * `ESO - European Southern Observatory <http://www.eso.org>`_

Feature Overview
----------------
The Python AVM Library is a light wrapper around the Python XMP Toolkit,
providing easy manipulation, extraction, and retrival of Astronomy Visualization
Metadata.


What is AVM?
------------
The astronomical education and public outreach (EPO) community plays a key
role in conveying the results of scientific research to the general public.
A key product of EPO development is a variety of non-scientific public image 
resources, both derived from scientific observations and created as artistic 
visualizations of scientific results. This refers to general image formats 
such as JPEG, TIFF, PNG, GIF, not scientific FITS datasets. Such resources 
are currently scattered across the internet in a variety of galleries and 
archives, but are not searchable in any coherent or unified way.

Just as Virtual Observatory (VO) standards open up all data archives to a 
common query engine, the EPO community will benefit greatly from a similar 
mechanism for image search and retrieval. Existing metadata standards for 
the Virtual Observatory are tailored to the management of research datasets 
and only cover EPO resources (like publication quality imagery) at the 
"collection" level and are thus insufficient for the needs of the EPO community.

The primary focus of the AVM is on print-ready and screen ready astronomical 
imagery, which has been rendered from telescopic observations (also known as 
"pretty pictures"). Such images can combine data acquired at different 
wavebands and from different observatories. While the primary intent is to cover 
data-derived astronomical images, there are broader uses as well. Specifically, 
the most general subset of this schema is also appropriate for describing artwork 
and illustrations of astronomical subject matter. This is covered in some detail 
in later sections.

The intended users of astronomical imagery cover a broad variety of fields: educators, 
students, journalists, enthusiasts, and scientists. The core set of required tags 
define the key elements needed in a practical database for identification of desired 
resources.  For example, one might choose to search for images of the Crab Nebula 
that include both X-ray and visible light elements, or for any images within 2 degrees 
of a specified location on the sky that include at least some data from the Spitzer 
Space Telescope.

Future plans include "multimedia modules" and "planetarium modules" into the AVM standard.