It primarily supports continuous simulation (system dynamics), with some discrete event and agent-based modelling capabilities.
Vensim provides a graphical modeling interface with stock and flow and causal loop diagrams, on top of a text-based system of equations in a declarative programming language.
It includes a patented method for interactive tracing of behavior through causal links in model structure (the patent expired in 2012),[1][2][3] as well as a language extension for automating quality control experiments on models called Reality Check.
There are multiple paths for cross sectional and time-series data import and export, including text files, spreadsheets and ODBC.
Models may be calibrated against data using optimization, Kalman Filtering[6] or Markov chain Monte Carlo methods.