Evolution of Enterprise Systems Architectures:

Process orientation in general and business process management in particular
are parts of a larger development that has been affecting the design of
information systems since its beginning: the evolution of enterprise systems
architectures.
Enterprise systems architectures are mainly composed of information systems.
These systems can be distinguished from software systems in the area
of embedded computing that control physical devices such as mobile phones,
cars, or airplanes. Business process management mainly deals with information
systems in the context of enterprise systems architectures.
The guiding principle of this evolution is separation of concerns, a principle
identified by Edsger Dijkstra and characterized by �focusing one�s attention
upon some aspect.� It is one of the key principles in handling the complexity
of computer systems.
While this principle has many applications in theoretical and applied computer
science, in the context of software systems design�and therefore also in
information systems design�it means identifying sets of related functionality
and packaging them in a subsystem with clearly identified responsibilities and
interfaces. Using this approach, complex and powerful software systems can
be engineered. Separation of concerns also facilitates reuse at a level of coarse
granularity, because well-specified functional units provided by subsystems
can be used by different applications.
Separation of concerns also facilitates response to change and is therefore
an important mechanism to support flexibility of software systems, because
individual subsystems can be modified or even exchanged with another subsystem
providing the same functionality without changing other parts of the
system�provided the interfaces remain stable.
Since local changes do not affect the overall system, a second guiding principle
of computer science is realized: information hiding, originally introduced
by David Parnas. Reasons for changes can be manifold: new requirements in
an ever-changing dynamic market environment, changes in technology, and
changes in legal regulations that need to be reflected in software systems.

While effective response to change is an important goal of any software system,
it is of particular relevance to business process management systems, as
will be detailed below.
Before addressing the evolution of enterprise systems architectures, the
understanding of software architectures as used in this book is described. In
general, software architectures play a central role in handling the complexity
of software systems.