An aspect of the invention includes transforming a source model to a target model. A source model is received and a transformation specification that includes a set of rules is accessed. Each rule includes a pattern description and a production component. The pattern description includes a pattern in the source model and the production component includes an algorithm for generating an output in the target model from the pattern. For each expression in the source model, the expression is decomposed into sub-expressions, matching rules in the transformation specification for the expression and the sub-expressions are detected, one of the matching rules having the most specific pattern description is selected, and the production component of the selected rule is executed to generate the output in the target model. The target model is created from the generated output.