as a satellite, launcher, an oil rig or a building. Open Concurrent Design Server (OCDS) The Open Concurrent Design Server is a software package developed under a European Space Agency contract. It was the first attempt of an ECSS-E-TM-10-25A implementation. The software was never used in production and its further development was cancelled. The Open Concurrent Design Tool (OCDT) is the successor of the OCDS Open Concurrent Design Tool (OCDT) OCDT is a client / server software package developed under a European Space Agency contract to enable efficient multi-disciplinary concurrent engineering of space systems in the early life cycle phases. The OCDT client is an add-in for Microsoft Excel® 2010/2013, that is integrated with Excel® to perform simple analysis and simulation. Other client tools for engineering analysis and simulation can also be integrated, through the use of OCDT adapters. The OCDT server consists of a front-end web-services processor (using a REST API) and a back-end PostgreSQL database system for the persistent storage of OCDT shareable data. The server is able to support concurrent teams of more than 20 users and synchronising their engineering model content twice a minute or faster. Typically each user would represent a different domain of expertise (discipline). The package is distributed under an ESA community open source software licence available for use and further development to users that qualify as a member of the OCDT Community. OCDT is being used in the ESA CDF The OCDT implements both Annex A (the formal UML model) and Annex C (the Webservices API). RHEA Group Concurrent Design Platform™ (CDP4) The Concurrent Design Platform (CDP™) of the RHEA Group is the main engineering tool to support multidisciplinary teams to perform Concurrent Design of complex systems. The CDP4, an evolution of the CDP3, is an ECSS-E-TM-10-25 Annex A and Annex C compliant implementation, as such it is 100% compatible with the ESA OCDT. The CDP4 is a client / server software solution implemented using C# and a Postgresql RDBMS. The CDP4 Webservices (the server component) can be hosted both on Linux using Mono and Microsoft Windows®. The CDP4-IME is the desktop application that is compatible with Microsoft Windows® 7/10. A Microsoft Excel® 2010/2013 Add-in integrates many of the functionalities of the CDP4 in Microsoft Excel® and is accessible through a dedicated Ribbon and Custom Task Panes. The CDP4 implements both Annex A (the formal UML model) and Annex C (the Webservices