Simile is a visual environment for developing continuous-systems models in biology, ecology and environmental science. In common with a number of other modelling environments, the user constructs a node-and-arc diagram describing a set of differential-algebraic equations, using a notation of stocks, flows and influences (termed 'System Dynamics'). Simile is, however, unusual in being object-based: part of the model diagram can be enclosed in an envelope to define a class of object. A class can have multiple instances, which can be created and destroyed dynamically. Class envelopes can be nested to represent composition, and reflexive and non-reflexive associations between classes are supported.
There are clear areas of convergence between object-based concepts in Simile, UML class diagrams, and other aspects of conventional object-oriented methods. However, there are also certain differences, reflecting the pattern of Simile development, the particular needs of System Dynamics modelling, and the way that we produce a runnable implementation of a model through program generation. The aim of the seminar is to open up a dialogue on the object design and implementation choices made in Simile, in relation to conventional object-oriented methods.