Efficient modelling necessitates standards for model documentation and exchange.

In this paper, problems related to simulation model documentation and model exchange between users are discussed. Complex simulation models have gained popularity in the environmental field, but require extensive documentation to allow independent implementation. The existence of different simulation platforms puts high demands on the quality of the original documentation. Recent experiences from cross-platform implementations with the ASM2d and ADM1 models reveal that error-free model documentation is difficult to obtain, and as a consequence, considerable time is spent on searching for documentation and implementation errors of various sources. As such, the list of errors and coding pitfalls provided for ASM2d and ADM1 in this paper is vital information for any future implementation of both models. The time needed to obtain an error-free model implementation can be significantly reduced if a standard language for model documentation and exchange is adopted. The extensible markup language (XML) and languages based on this format may provide a remedy to the problem of platform independent model documentation and exchange. In this paper the possibility to apply this to environmental models is discussed, whereas the practical model implementation examples corroborate the necessity for a standardised approach.