Overview


Although DFTS is a design-focused quality technology, it also includes problem-solving/process-improvement capabilities and can benefit from the deployment of the Seven Basic (B7) Tools, widely used in manufacturing. In a DFTS context, B7 tools can be of great value in project management, inspection, and testing and in analyzing software metrics. They can also be used in upstream design phases, except for statistical tools such as control charts, histograms, and scatter diagrams that require larger volumes of data to be statistically significant. The most frequently used B7 tools, such as cause-andeffect and Pareto diagrams, are not quantitative, let alone statistical. B7 thus constitutes a useful toolkit in the software development context both in process improvement and design tools, of which a few are indispensable.

It is important to use them in the wider context of DFTS technology, which includes a number of quality methodologies, such as QFD, TRIZ, Pugh, Taguchi Methods, and FMEA, which are discussed later in this book. Additionally, techniques such as systems thinking, process management, standardization, and adequate documentation, which are an integral part of DFTS technology, must be included in process improvement.

A flowchart graphically represents various activities in a sequential manner. Identifying such activities and their causes can help eliminate or minimize redundancies and wasteful activities as well as strengthen those that help achieve process goals and create customer value. It also serves as a communication tool.

Cause-and-effect diagrams are also called fishbone diagrams, because of their structure, or Ishikawa diagrams, for Kaoru Ishikawa, who developed this tool. These are among the most widely used tools in quality management; they are used for the following purposes: identifying causes of variation and taking countermeasures, process classification, Pareto-Ishikawa, generating data needed for FMEA, identifying possible "noise" and "control factors" in Taguchi Methods, as a visible communication tool, and categorizing various inputs (causes) and outputs (effects).

A scatter diagram seeks to establish whether a relationship exists between two variables and the strength of the relationship. Establishing relationships can be particularly useful in cause-and-effect analysis. A strong correlation may help identify possible countermeasures to address a particular quality problem.

A check sheet is a paper form that lists items to be measured, checked, and recorded. It makes data collection easy, usable, and standardized by the form's particular design. Various check sheets are possible, depending on the objective of the data collection exercise, such as measuring process variation, analyzing types of defects, and identifying causes of defects. They are often coupled with histograms to display visualization and use of data collected in histograms.

A histogram is used to analyze variation in a set of data. It helps you understand how the data collected from a particular development or production process is distributed in terms of frequency of occurrences of a particular value in the set. The key objective is to look for stability and predictability.

Graphs are useful tools in software quality and project management. Among the most commonly used graphs are run charts, pie charts, and bar charts. They help you monitor time variation and understand causes of defects in a process.

Control charts are among the most important quality tools. They measure process variation periodically to check whether it is within acceptable limits. Processes whose variation is within such limits are said to be "in control." "Out-of-control" processes lead to defective work with adverse cost, quality, and schedule implications. Statistical Process Control (SPC) deploys control charts to prevent defective work by focusing efforts on process quality rather than the final product. It thus lets the enterprise take preventive and process improvement initiatives instead of just appraising the final product. XmR charts and average (X-bar) and range (R) charts have been found to be most useful to measure software process.

This chapter introduces B7 in a software development context and is a precursor to Chapter 15.

Chapter Outline

  • The Seven Basic (B7) Tools

  • B7 in a DFTS Context

  • Other DFTS Tools, Techniques, and Methodologies

  • Flowcharts

  • Pareto Charts

  • Cause-and-Effect Diagrams

  • Scatter Diagrams

  • Check Sheets

  • Histograms

  • Graphs

  • Control Charts

  • Key Points

  • Additional Resources

  • Review Questions

  • Discussion Questions

  • Endnotes




Design for Trustworthy Software. Tools, Techniques, and Methodology of Developing Robust Software
Design for Trustworthy Software: Tools, Techniques, and Methodology of Developing Robust Software
ISBN: 0131872508
EAN: 2147483647
Year: 2006
Pages: 394

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