The main elements of abstract models are classes providing an abstraction of the specialties of real environments. This contrasts the components of environmental models, which deal with objects directly mappable to the real world. The dependencies between the classes are specified on the same level of abstraction. It is easy to see that environmental models actually are instantiations of abstract models--of their objects as well as their dependencies.
Simple Abstract Service Dependency Graph
The model shown in figure looks similar to the previous one. However--as each node now depicts a class--both web clients are covered by a single ``web client'' element. Following object oriented principles, the nodes' and edges' attributes are now replaced by definitions for allowed, resp. needed attributes.