* **Conceptual integrity**: "It is better to have a system omit certain anomalous features and improvements, but to reflect one set of design ideas, than to have one that contains many good but independent and uncoordinated ideas." ([Fred Brooks](http://wiki.c2.com/?ConceptualIntegrity))
* **Stability** is the sensitivity to change of a given system that is the negative impact that may be caused by system changes ([ISO/IEC 9126 standard on evaluating software quality](https://en.wikipedia.org/wiki/ISO/IEC_9126)).
* **Reliability** is made of maturity (frequency of failure in software), fault tolerance (ability to withstand failure) and recoverability (ability to bring back a failed system to full operation) ([ISO/IEC 9126 standard on evaluating software quality](https://en.wikipedia.org/wiki/ISO/IEC_9126)).