Training system requirements managers have a unique challenge in the form of documenting the qualitative and quantitative requirements of hardware and software systems whose principal purpose is the support of training outcomes for the people that use them. In the United States Department of Defense and similar organizations, capability requirements policies and processes, i.e. the Joint Capabilities Integration and Development System (JCIDS), are oriented on weapon systems. By default, training systems are considered ancillary components of the associated weapon systems. For various reasons, though, some training systems must be developed as independent capabilities rather than footnotes to larger systems. JDICS-type documents consist of two fundamental components: capability requirements, which describe “what” a system must be able to do, and performance attributes, which prescribe threshold and objective (hard minimum and reasonable maximum) measures of “how well” the capability requirements should be met. It turns out that determining performance attributes for training systems can be extremely challenging; typical weapon system attributes such as speed, range, engagement distance, weight, and survivability are essentially meaningless for training systems. The core attribute of a training system is the extent to which it enables training against a set of standards, but those standards can—and must—change as the operating environment evolves. Processes such as JCIDS are not agile enough to respond to changes to the training standards. This paper offers some approaches to determining quantifiable performance attributes for training systems in a JCIDS-type context. It also describes a methodology for adapting requirements at a pace that maintains relevance to the operating environment. Although JCIDS is the main focus, consideration is given to related processes such as Front End Analysis and Training Effectiveness Evaluation. This paper provides tools that will help training system capability developers succeed, even within processes designed for weapon systems.