Before an architecture for a software system (or package) --- that is:
a definition of concepts and facilities of the software system (resp.\
package) to be developed --- can be given, one first establishes
proper requirements expected of that software, that is: we base
software development on requirements specifications.  These
requirements are captured from understanding first the domain in which
the software is to serve and then from understanding the expectations
of the new software as an operational part of the thus extended
domain. Thus understanding the domain seems to be a very first order
of `business'! In this paper we present an example of the collection
of (informal) procedures and (formal) techniques that are being
applied in understanding the Railway System domain --- as part of a
large scale technology transfer project joint with various software
development and computer centers of the Chinese Railways in
researching and developing proper software eventually for all aspects
of railway operation in China.