Excerpt from Comparing Three Approaches to Transformational Programming<br><br>Programming is a complex task; large programs are difficult to produce, and once produced they are often unreliable and expensive to maintain or improve. The software crisis remains an important issue in software engineering. A large amount of research has been going on to overcome this crisis: On one hand, a considerable portion of the work has focused on formalizing and automating the software development process; on the other hand, prototyping has been promoted as a method of obtaining information about a problem before implementing it in a production language.<br><br>Traditionally, programs have been verified experimentally by choosing a number of input test cases, running the program, and evaluating the results. -the problem with this approach is that it can never formally prove the correctness of the program. There might always be cases not captured by the test data. Prototyping attempts to catch errors at an early a stage of the program development.<br><br>Formal verification, on the other hand, is an analytic process that defines in mathematical terms what it means for a program to be correct, given a mathematical definition of the program ming language used, and a formal specification of the problem being solved. However, the formal verification of large programs has turned out to be impractical.<br><br>By contrast, the transformational approach (see [pss3] for an excellent survey) is a synthetic or constructive one. A program is derived from a problem specification by successive application of correctness-preserving transformations that lead to a correct implementation of the problem. A key point is the reusability of transformation rules; once a rule is proven correct, it can be used again if applicable to the particular situation. Libraries of known transformations can be established; as the libraries grow, the number of new proofs required in the development of a. Program decreases.<br><br>About the Publisher<br><br>Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com<br><br>This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.