Other derivative frameworks based on DoDAF include the NATO Architecture Framework (NAF) and Ministry of Defence Architecture Framework. Like other EA approaches, for example The Open Group Architecture Framework (TOGAF), DoDAF is organized around a shared repository to hold work products. The repository is defined by the common database schema Core Architecture Data Model 2.0 and the DoD Architecture Registry System (DARS). A key feature of DoDAF is interoperability, which is organized as a series of levels, called Levels of Information System Interoperability (LISI). The developing system must not only meet its internal data needs but also those of the operational framework into which it is set.