Measuring Architecture Principles and Their Sets in Practice: Creating an Architecture Principle Measurement Instrument Challenged in a Case Study at the Dutch Tax Agency Topics: Architectures and Design Principles for Enterprise Repositories; Measurements, Metrics and Evaluation of EA Artefacts and Processes; Models and Frameworks In Proceedings of the 21st International Conference on Enterprise Information Systems - Volume 2: ICEIS, 534-543, 2019 , Heraklion, Crete, Greece