Information Technology Reference
In-Depth Information
The DFX family of tools collect and present facts about both the design entity
and its production processes, analyze all relationships between them, measure the
critical-to-quality (CTQs) of performance as depicted by the software architecture,
generate alternatives by combining strengths and avoiding vulnerabilities, provide a
redesign recommendation for improvement, provide if-then scenarios, and do all that
with many iterations.
The objective of this chapter is to introduce the vital few of the software DFX
family. The software DFSS team should take advantage of, and strive to design into,
the existing capabilities of suppliers, internal plants, and assembly lines. It is cost-
effective, at least for the near-term. The idea is to create software sufficiently robust
to achieve Six Sigma performance from current capability.
The key “design for” activities to be tackled by the team are:
1. Use DFX as early as possible in the software DFSS process.
2. Start with software design for reliability (DFR).
3. Based on the findings of (2), determine what DFX to use next. This is a function
of DFSS team competence. Time and resources need to be provided to carry
out the “design for” activities. The major challenge is implementation.
A danger lurks in the DFX methodologies that can curtail or limit the pursuit
of excellence. Time and resource constraints can tempt software DFSS teams to
accept the unacceptable on the premise that the shortfall can be corrected in one of
the subsequent steps—the second chance syndrome. Just as wrong concepts cannot
be recovered by brilliant detail design, bad first-instance detail designs cannot be
recovered through failure mode analysis, optimization, or fault tolerancing.
14.2
SOFTWARE RELIABILITY AND DESIGN FOR RELIABILITY
Software reliability is a key part in software quality. Software quality measures how
well software is designed (quality of design), and how well the software conforms to
that design (quality of conformance), although there are several different definitions.
Whereas quality of conformance is concerned with implementation, quality of design
measures how valid the design and requirements are in creating a worthwhile product.
ISO 9126 is an international standard for the evaluation of software quality. The
fundamental objective of this standard is to address some of the well-known human
biases that adversely can affect the delivery and perception of a software development
project. These biases include changing priorities after the start of a project or not
having any clear definitions of “success.” By clarifying then agreeing on the project
priorities and subsequently converting abstract priorities (compliance) to measurable
values (output data can be validated against schema X with zero intervention), ISO
9126 tries to develop a common understanding of the projects objectives and goals.
The standard is divided into four parts: quality model, external metrics, internal
metrics, and quality in use metrics. Each quality subcharacteristic (e.g., adaptability)
Search WWH ::
Custom Search