interTwin co-designs and implements the prototype of an interdisciplinary Digital Twin Engine (DTE). The developed DTE will be an open source platform that includes software components for modelling and simulation to integrate application-specific Digital Twins. InterTwin WP6 will provide the core DTE modules to be integrated by WP7 and to be executed on infrastructure and components delivered by WP5. The current document consists of a report on the high-level description of WP6 components and the related design based on the C4 model. Additionally, this deliverable includes the set of requirements derived from the analysis of the use cases.