xia2 is an expert system to perform X-ray diffraction data processing on your behalf, using your software with little or no input from you. It will correctly handle multi-pass, multi-wavelength data sets as described later but it is not a data processing package. Specifically, if you use xia2 in published work please include the references for the programs it has used, which are printed at the end of the output. The system was initially written to support remote access to synchrotron facilities, however it may prove useful to anyone using MX, for example:

• assisting new or novice users,
• giving a second opinion to experts,
• assisting busy users to allow them to focus on problem cases, or
• providing reproducible processing.

The last of these may be most useful for users in a pharmaceutical setting, or people wishing to test or benchmark equipment, for example beamline scientists. In all cases however the usage of the program is the same.