* **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))
* **End-to-end principle**: "application-specific features reside in the communicating end nodes of the network, rather than in intermediary nodes" ([end-to-end principle - Wikipedia](https://en.wikipedia.org/wiki/End-to-end_principle))
* **[NIHITO](http://pragmaticmarketing.com/resources/use-the-market-to-gain-credibility)** (Nothing Important Happens In The Office): you need to learn from your customers and from the market first.
* **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)).
* **Two Generals' Problem**: "a thought experiment meant to illustrate the pitfalls and design challenges of attempting to coordinate an action by communicating over an unreliable link" ([wikipedia](https://en.wikipedia.org/wiki/Two_Generals%27_Problem)).
* **Law of Demeter**: only talk to your immediate friends ([wikipedia](https://en.wikipedia.org/wiki/Law_of_Demeter))
### Second system effect
"The second-system effect (also known as second-system syndrome) is the tendency of small, elegant, and successful systems to be plagued with feature creep due to inflated expectations." ([wikipedia](https://en.wikipedia.org/wiki/Second-system_effect))
