  One of the scientific objectives of the Ooty Wide Field Array(OWFA) is to
observe the redshifted HI emission from z ~ 3.35. Although predictions spell
out optimistic outcomes in reasonable integration times, these studies were
based purely on analytical assumptions, without accounting for limiting
systematics. A software model for OWFA has been developed with a view to
understanding the instrument-induced systematics, by describing a complete
software model for the instrument. This model has been implemented through a
suite of programs, together called Prowess, which has been conceived with a
dual role of an emulator as well as observatory data analysis software. The
programming philosophy followed in building Prowess enables any user to define
an own set of functions and add new functionality. This paper describes a
co-ordinate system suitable for OWFA in which the baselines are defined. The
foregrounds are simulated from their angular power spectra. The visibilities
are then computed from the foregrounds. These visibilities are then used for
further processing, such as calibration and power spectrum estimation. The
package allows for rich visualisation features in multiple output formats in an
interactive fashion, giving the user an intuitive feel for the data. Prowess
has been extensively used for numerical predictions of the foregrounds for the
OWFA HI experiment.
