  We present a data format for the output of general N-body simulations,
allowing the presence of individual time steps. By specifying a standard,
different N-body integrators and different visualization and analysis programs
can all share the simulation data, independent of the type of programs used to
produce the data. Our Particle Stream Data Format, PSDF, is specified in YAML,
based on the same approach as XML but with a simpler syntax. Together with a
specification of PSDF, we provide background and motivation, as well as
specific examples in a variety of computer languages. We also offer a web site
from which these examples can be retrieved, in order to make it easy to augment
existing codes in order to give them the option to produce PSDF output.
