  Software Defined Networking is currently revolutionizing computer networking
by decoupling the network control (control plane) from the forwarding functions
(data plane) enabling the network control to become directly programmable and
the underlying infrastructure to be abstracted for applications and network
services. Next to the well-known OpenFlow protocol, the XML-based NETCONF
protocol is also an important means for exchanging configuration information
from a management platform and is nowadays even part of OpenFlow. In
combination with NETCONF, YANG is the corresponding protocol that defines the
associated data structures supporting virtually all network configuration
protocols. YANG itself is a semantically rich language, which -- in order to
facilitate familiarization with the relevant subject -- is often visualized to
involve other experts or developers and to support them by their daily work
(writing applications which make use of YANG). In order to support this
process, this paper presents an novel approach to optimize and simplify YANG
data models to assist further discussions with the management and
implementations (especially of interfaces) to reduce complexity. Therefore, we
have defined a bidirectional mapping of YANG to UML and developed a tool that
renders the created UML diagrams. This combines the benefits to use the formal
language YANG with automatically maintained UML diagrams to involve other
experts or developers, closing the gap between technically improved data models
and their human readability.
