The Importance of Quality Criteria
The quality requirements encompass all levels of software production.
Poor quality in intermediate products always proves detrimental to the quality of the final product.
• Quality attributes that affect the end product
• Quality attributes that affect intermediate products
Quality of end products [Bons 1982]:
• Quality attributes that affect their application: These influence the suitability of the product for its intended application (correctness, reliability and user friendliness).
• Quality attributes related to their maintenance: These affect the suitability of the product for functional modification and extensibility (readability, extensibility and testability).
• Quality attributes that influence their portability: These affect the suitability of the product for porting to another environment (portability and testability).
Quality attributes of intermediate products:
• Quality attributes that affect the transformation: These affect the suitability of an intermediate product for immediate transformation to a subsequent (high-quality) product (correctness, readability and testability).
• Quality attributes that affect the quality of the end product: These directly influence the quality of the end product (correctness, reliability, adequacy, readability, extensibility, testability, efficiency and portability).

The effects of quality criteria on each other

Mutual effects between quality criteria (“+”: positive effect, “-“: negative effect, “0”: no effect)

Quality assurance measures
The most important measures are:
1. Constructive measures:
• Consistent application of methods in all phases of the development process
• Use of adequate development tools
• Software development on the basis of high-quality semifinished products
• Consistent maintenance of development documentation
2. Analytical measures:
• Static program analysis
• Dynamic program analysis
• Systematic choice of adequate test cases
• Consistent logging of analysis results
3. Organizational measures:
• Continuous education of product developers
• Institutionalization of quality assurance