02003nas a2200253   4500008003900000245009500039210006900134260001200203300001400215490000700229520119300236653005301429653001501482653001101497653001901508653001501527653002601542653001101568653001101579653001801590100001501608700001501623856011101638       2005                          d00a“It was an artefact not the result”: A note on systems dynamic model development tools0 aIt was an artefact not the result A note on systems dynamic mode  c12/2005  a1543-15480 v203 a<p>Environmental modelling is done more and more by practising ecologists rather than computer scientists or mathematicians. This is because there is a broad spectrum of development tools available that allows graphical coding of complex models of dynamic systems and help to abstract from the mathematical issues of the modelled system and the related numerical problems for estimating solutions. In this contribution, we study how different modelling tools treat a test system, a highly non-linear predator&ndash;prey model, and how the numerical solutions vary. We can show that solutions (a) differ if different development tools are chosen but the same numerical procedure is selected; (b) depend on undocumented implementation details; (c) vary even for the same tool but for different versions; and (d) are generated but with no notifications on numerical problems even if these could be identified. We conclude that improved documentation of numeric methods used in the modelling software is essential to make sure that process based models formulated in terms of these modelling packages do not become &ldquo;black box&rdquo; models due to uncertainty in integration methods.</p>10aLotka-Volterra equation; Predator-prey modelling10aMATEMATICA10aMATLAB10aModel analysis10aMODELMAKER10aNumerical ODE solvers10aSimile10aSTELLA10aStiff systems1 aSeppelt, R1 aRichter, O  u//www.simulistics.com/publications/it-was-artefact-not-result-note-systems-dynamic-model-development-tools