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44 PART ONE THE PRODUCT AND THE PROCESS

therefore enable the software engineer to discover and correct errors that might
go undetected.
Although it is not destined to become a mainstream approach, the formal meth-
ods model offers the promise of defect-free software. Yet, the following concerns
about its applicability in a business environment have been voiced:
1. The development of formal models is currently quite time consuming and
expensive.
2. Because few software developers have the necessary background to apply
formal methods, extensive training is required.
3. It is difficult to use the models as a communication mechanism for techni-
cally unsophisticated customers.
These concerns notwithstanding, it is likely that the formal methods approach will
gain adherents among software developers who must build safety-critical software
(e.g., developers of aircraft avionics and medical devices) and among developers that
would suffer severe economic hardship should software errors occur.

2.10 FOURTH GENERATION TECHNIQUES

The term fourth generation techniques (4GT) encompasses a broad array of soft-
ware tools that have one thing in common: each enables the software engineer
to specify some characteristic of software at a high level. The tool then automat-
ically generates source code based on the developer's specification. There is lit-
tle debate that the higher the level at which software can be specified to a machine,
the faster a program can be built. The 4GT paradigm for software engineering
focuses on the ability to specify software using specialized language forms or a
graphic notation that describes the problem to be solved in terms that the cus-
tomer can understand.
Currently, a software development environment that supports the 4GT paradigm
includes some or all of the following tools: nonprocedural languages for database
query, report generation, data manipulation, screen interaction and definition, code
generation; high-level graphics capability; spreadsheet capability, and automated
generation of HTML and similar languages used for Web-site creation using advanced
software tools. Initially, many of the tools noted previously were available only for
very specific application domains, but today 4GT environments have been extended
to address most software application categories.
Like other paradigms, 4GT begins with a requirements gathering step. Ideally, the
customer would describe requirements and these would be directly translated into
an operational prototype. But this is unworkable. The customer may be unsure of
what is required, may be ambiguous in specifying facts that are known, and may be
unable or unwilling to specify information in a manner that a 4GT tool can consume.