1 of 15 C:\Documents and Settings\bruce\My Documents\Papers\manifesto for open software\Licences-Journal-web.doc Created 2007-02-13 Modified 2007-02-13 Printed 2007-02-13 Towards a manifesto for open simulation J. Gary Polhill Macaulay Institute, Craigiebuckler, Aberdeen. AB14 0PR. United Kingdom. g.polhill@macaulay.ac.uk Bruce Edmonds Centre for Policy Modelling, Manchester Metropolitan University, Aytoun Building, Aytoun Street. M1 3GH. United Kingdom. bruce@edmonds.name Abstract The difficulties associated with adequately describing agent-based social simulation software in scientific journals necessitate the establishment of norms for making the software more accessible. We consider here norms for documentation and licensing that outline a manifesto for open simulation, which we hope the community will sign up to. Licensing in particular has a number of thorny issues associated with it: the default under the Berne Convention turns software into a black box, raising a question over whether it can form a legitimate part of the domain of scientific discourse, or for that matter, of open and accountable government. Researchers must therefore take action to ensure their software is not released under an inappropriate licence. We recommend that a manifesto be produced based on the proposals in this paper, and call upon researchers to (a) sign up to that manifesto; (b) implement its proposals; (c) comment on licences when reviewing articles and proposals; (d) encourage others to do the same. Keywords: Agent-Based Social Simulation, Replication, Software Licences, Documentation, Archiving. 1. Introduction Even the best social simulations are complex objects whose meaning and import are difficult to discern. One may read a description of a simulation and get a vague idea of its properties but, like mathematics, one only thoroughly understands a simulation when one has pulled it apart and played with it. Despite this fact, simulations have become part of the scientific discourse and are starting to enter the more general, public, discourse. In public domains simulations are often communicated without deep hands-on understanding, relying instead upon the skill and integrity of the community who created them. In this sense they are like mathematical models, simultaneously opaque to most and relied upon by many. However, unlike mathematical models, they facilitate attractive and accessible animations of their results—making them seem more transparent than they are and persuasive to a degree quite separate from their validity. For these reasons it is important that simulations are openly accessible to others so that they can be checked, compared and improved upon. In this way they can be passed-on and developed by a series of independent researchers resulting in objects that are reliable and thoroughly understood (as far as this is completely possible). Indeed the simulations can be said to be evolved by the community of simulators. The easier it is to download, reimplement, compare, alter and try out the simulations, the more productive this process will be and the better its results. Some of these issues are discussed by more general calls to the social simulation community looking at open content issues (Schweik, Evans and Grove 2005) and understanding what simulations do (Alessa, Laituri and Barton 2006). In a democratic society where simulations are used as an input to the formulation of policy there is a further reason why the simulations should be open. A simulation is not value-free but