| In the past few years, object-oriented techniques have finally made the passage
from the programming-in-the-small island to the mainland of programming-inthe-
large. Accompanying this transition has been a change in the role and
perception of software methods: in addition to their well-established use in the
earliest stages of a project—requirements analysis and system specification—
they are increasingly viewed as providing the intellectual support needed across
the entire software construction process, through design and implementation to
maintenance and reengineering. The object-oriented approach is best suited to
achieve this seamlessness of the software development process, without which it
would not be possible to meet the quality and productivity challenges that
confront the software industry.
This book shows how a consistent set of object-oriented abstractions can be
applied throughout the process, based on three major ideas: seamlessness,
reversibility, and contracting.
Seamlessness, as in the first word of the title, follows from the observation
that the similarities between the tasks to be carried out at the various steps of a
project far outweigh their inevitable differences, making it possible to obtain a
continuous process that facilitates communication between the various actors
involved, ensures a direct mapping between a problem and its software solution,
and results in a high level of quality for the final product.
Reversibility means that the seamless procedure must work in both directions:
if one modifies a system that has already reached the implementation phase—a
frequent case in practice—it must be possible to reflect the modification back to
the higher levels of design, specification, and analysis. Without such
reversibility the products of these earlier stages would soon become obsolete,
raising disturbing questions about their very role in the software process. Since
current object-oriented methods are still dominated by hybrid approaches—that
is to say, encumber the application of object-oriented principles with techniques
drawn from non-object-oriented analysis methods and with constructs drawn
from non-object-oriented languages—reversibility has so far been almost absent
from the concerns of the object-oriented literature. |
