Methods and apparatus, including computer program products, for defining and using a service meta model operate on a meta model that includes an object node class, an association class, and an object class. The object node class includes a key identifier and represents data types. The association class is associated with the object node class and represents an association between instances of the object node class. The object class is associated with an object composition. The object composition is defined by a data structure of instances of the object node class and associations between the instances of the object node class represented by the association class.