A Capability Case is a way to express aspects of a solution through stories of real (or envisioned) use within a business context. In requirements work, Capability Cases allow a shared vision of a solution to be developed by business people, technical people and other stakeholders. Upstream from Use Cases they support the conversation about "what the system should be" as opposed to "how the system will work". (NU)
Capability Cases are a way of "conceptualizing a system". Identifying capabilities early provides a means to talking about the major pieces of functionality of the system. High level use cases are still important to contextualizing the process of nominating and creating Capability Cases. Detailed use cases can only be done when the nature of the system has been determined. (NV)
Capability Cases serve as catalysts to "spark" the thinking on what is possible through technology and at the same time ground the creative work in the reality of what the business is experiencing. Capability cases help to bridge the gap between business at IT. More on capability cases can be found at http://www.topquadrant.com/TopDrawer/TQcapabilitycases.htm. (NW)
Some collections of capability cases can be found at http://www.topquadrant.com/TopDrawer_Gallery/TQgallery_home.htm (NX)