We outline basic aspects of a method for developing systems.  The
method concerns a sequentially ordered set of development stages.  For
each stage we describe principles and techniques. The major stages
include: problem delineation, domain theory, requirements capture and
software development. Each stage may consist of several partially
ordered related steps. Typical software development steps include the
(externally observable) software architecture, the (internally
structuring) program organisation, zero, one or more software design
steps and the [final] code step.  Development work within stages and
steps are recorded in descriptions. Such documents contain both
informal parts: synopsis, narrative and terminology, and formal parts.
The latter are expressed in a number of relatable design calculi.  \\
An emphasis of the method is its applicability to very large scale
infra\-structure systems. An infrastructure system is seen as a base
and a set of extensions. Each base + extension defines the terms of a
sub-language --- the professional language spoken by employees of an
appropriate subpart of the infrastructure.  \\ The method is
formulated around a concept of Problem Frames introduced by Michael
Jackson.