Guest editorial to the special section on model transformation

Modeling is a key element in reducing the complexity of the development and maintenance of software systems. Software engineering paradigms like model-driven engineering (MDE) consider models as the primary elements in the software construction process. In this setting, model transformations are essential for elevating models from documentation elements to first-class artifacts of the development. Model transformation includesmodel-to-text transformation to generate code from models, text-to-model transformations to parse textual representations tomodel representations,model extraction to derive higher-level models from legacy code, and model-to-model transformations to normalize, weave, optimize, simulate, and refactor models, as well as to translate between modeling languages. Model transformation encompasses a variety of technical spaces, including modelware, grammarware, and XMLware, a variety of transformation representations, including graphs, trees, and DAGs, and a variety of transformation paradigms, including rule-based graph transformation, term rewriting, and implementations in general-purpose programming languages. The study of model transformation includes foundations, semantics, structuring mechanisms, and properties (such as