The figure shows three types of data processing that are available in the beta release of the ARCS software. The Raw Data are depicted towards the upper left of the figure. The results at different stages of data processing can be viewed with components such as Grace, Matplotlib and Gnuplot. Bindings are provided so users with licensed copies of Matlab and IDL can integrate them in an analysis network. The three essential types of data processing provided by the ARCS software are:

• The top row of data operations, labeled "Reduction," is the traditional path for transforming time-of-flight histograms into the scattering intensity S(Q,E). This functionality is provided for powder and isotropic scatterers. Some additional tools are provided without full integration into the pyre framework.

• The vertical path labeled "Simulation" indicates another way to do data analysis. A full simulation of the instrument and the sample will follow each individual neutron from moderator to detector, and the counts on the detector can be compared to experiments. A simulation application can be constructed from a template in the "simulation" package. Currently most neutron components for such simulations are based on those from the McStas package from Riso, distributed under a GPL license. Most McStas components have been adapted to the pyre framework. In addition, a "sample" component is available. The sample component can contain a number of different scatterers and scattering kernels such as incoherent inelastic scattering, and/or coherent inelastic scattering.

• Some limited functionality is provided for the vertical path labeled "Modeling." Forward codes for lattice dynamics and Heisenberg dynamics are provided. Optimization algorithms are still under development and are not part of the present release.

All ARCS software runs under the pyre framework version 0.8, which is included in the beta release. Pyre gives an interpretive environment that offers a quick way to change an analysis network without recompilation. The large applications in the beta relase are pyre scripts of smaller software components, typically written in Python or C++ with Python bindings. The documentation shows the composition of applications such as "reduction," and some examples of modifications are given. It is expected that most users would want to swap out the visualization packages, for example.

Documentation at lower levels of detail, such as UML class diagrams, is provided on the DANSE MediaWiki. The present site should help you navigate through this more detailed information. README files are also available, and we have given some examples for experimentation.

The ARCS software project is an open source effort, and the software is released primarily under the MIT/X11 license, a variant of the BSD license, with some components under the GPL license. This beta release of the ARCS software is intended primarily for internal evalulation by participants in the ARCS and DANSE projects, and by SNS personnel. Others are welcome to experiment with it. We welcome your feedback, but we are unable to provide systematic support.