DoDAF has a meta-model underpinning the framework, defining the types of modelling elements that can be used in each view and the relationships between them. DoDAF versions 1.0 thru 1.5 used the CADM meta-model, which was defined in IDEF1X (then later in UML) with an XML Schema derived from the resulting relational database. From version 2.0, DoDAF has adopted the IDEAS Group foundation ontology as the basis for its new meta-model. This new meta-model is called "DM2"; an acronym for "DoDAF Meta-Model". Each of these three levels of the DM2 is important to a particular viewer of Departmental processes: