Ventity is new software for System Dynamics and simulation of complex systems.

Download a copy here.

The really big change from most simulation languages is that we’ve replaced arrays with collections of entities, identified by attributes. This makes for a more natural and data-friendly problem description. Detail becomes a property of entities, not equations, which makes it a lot easier to coordinate and change.

Entities are modular, so they’re easier to reuse and share among teams. Entities can be created and deleted dynamically, so there’s no need to simulate a lot of zeroes for things that haven’t happened yet. Similarly, a list of entity relationships can represent a sparse matrix, so there’s no need to clutter your model with zeroes for project phases that aren’t prerequisites or relationships that don’t exist among people. All this happens in a development environment with modern, interactive charts and windowing.

Key features include:


  • Consumer products: build a marketing mix model for a portfolio of products across multiple regional markets, distribution channels, brands and package sizes. Not all of the brands are present in each market, and package options differ for each brand. In traditional SD, it takes a lot of data work to standardize things to work with arrays. With entities, it’s easy – we create a Product entity identified by an SKU, with Market, Channel, Brand and Package attributes, and we simply don’t bother to create combinations that don’t exist. Later, when new products launch, we can add them to the model on the fly.
  • Health care:  understand the diffusion of information about treatments through the social network of doctors. Doctors don’t know every other doctor, but they’re sparsely related through common practices, specialties and patient referrals. We can explore this as a full agent model, or a semi-aggregate model, in which information is well-mixed within organizations.
  • Energy: model a building portfolio with construction and retrofits, preserving the age distribution of buildings without suffering the limitations of coflows and discrete delays.
  • Environment: build an integrated assessment model that can change the granularity of emissions from state to country to region to globe at the flip of a switch.
  • Logistics: simulate a supply chain, specifying the links among levels with data.

Vensim or Ventity?

Ventity doesn’t replace Vensim; they’re complementary. Each has strengths for particular types of problems. Both platforms can do classic System Dynamics and light discrete event simulation. We continue to develop them in parallel.

Choose Ventity for … Choose Vensim for …
  • dynamic structure change, like the introduction of new firms to a market
  • easy cohort modeling without age dispersion
  • sparse matrices, like project prerequisites and social networks
  • team model building, with entities managed by different users
  • natural fit to relational and tidy data with ad hoc attributes
  • reuse of entities in new models, or models with new data
  • simulation against real calendar time
  • autocomplete and drag-and-drop
  • ABM with complex agents, no programming needed
  • running multiple scenarios with a single click
  • free PLE for education
  • a huge installed base of teaching materials, papers, books and models
  • extreme speed
  • causal loop diagramming
  • builtin functions for delays, conveyors and queues
  • problems that naturally fit combinatorial arrays
  • redistribution with Venapp, Sable or the .DLL
  • advanced algorithms
    • sensitivity simulation
    • random multistart optimization
    • Markov Chain Monte Carlo
    • Kalman Filtering

Further Reading

There’s a Ventity poster and more detailed white paper in the SD conference proceedings: