Model-driven software engineering is a well-known concept in computer science, but scarcely applied in chemical engineering. This contribution presents a first implementation of model-driven development of customized code for simulation and optimization based on equation-oriented models in process science. Transferring the model-driven approach to chemical engineering allows for transformations or discretizations before automated code generation. The customization of this concept poses additional challenges regarding flexibility and tailoring for the user's needs. We propose the so-called "User-defined Language Specificators (UDLS)", based on free standards (MathML, XML), to combine the benefits of automated code generation with the flexibility of customization, therefore still avoiding error-prone manual model implementation. The case studies show the successful application of this approach for equation-based flowsheet simulation (using CAPE-OPEN interfaces) as well as optimization. (C) 2018 Elsevier Ltd. All rights reserved.