To realise the benefits of maritime autonomous technologies at scale, new measures of confidence are required for technologies where critical decisions are not being made by humans, and where safety must be maintained through operations The draft IMO MASS code represents a significant sign of progress, yet its high level nature means it is subject to interpretation. In response to these challenges and needs; the Maritime Autonomy Assurance Testbed (MAAT) programme is being set up to deliver an internationally relevant assurance capability for Maritime Autonomy, supported by pro-innovation standards. Based in Plymouth, MAAT first MASS sensor / environmental test range is now live and gathering data to support test programmes. This presentation will show how compliance can be assessed against concrete evidence, which includes generating traceable evidence back to structured requirements using common taxonomies, which can be interpreted by machines and multiple stakeholders. This will take a look at the development of the ISO standards on ODD and OE taxonomies, mandated through the IMO MASS code, and will summarise the relationship and distinction between these artifacts and CONOPS.