# Software Architecture Principles and Quotes

This document contains a curated collection of software architecture principles, design philosophies, and engineering wisdom from various experts in the field.

## Core Design Principles

### Fundamental Rules

| Principle | Description | Source |
|-----------|-------------|---------|
| Rule of Zero, One or Infinity (ZOI) | Arbitrary limits on the number of instances of a particular entity should not be allowed | Willem van der Poel |
| Worse is better | Design for simplicity | Richard P. Gabriel, 'Lisp: Good News, Bad News, How to Win Big' (1989) |
| Uniform Access Principle | Services should be offered through uniform interfaces, regardless of internal implementation | Bertrand Meyer |
| Rule of Least Power | Use the least powerful language possible for a given problem. Prefer declarative languages over procedural | - |
| Rule 3.14 | Nothing gets standardised until there are multiple instances of running code | RFC1958 (1996) |

### Classical Engineering Wisdom

| Quote | Attribution |
|-------|-------------|
| "I can get another if I break it, so a clay cup trumps a grail" | Mirza Asadullah Khan Ghalib, classical Urdu and Persian poet from the Mughal Empire |
| "Firmitas, utilitas, venusitas. (Firmness, utility, delight)" | Marcus Vitruvius, 'De Architectura' (22BCE) |
| "There is no excellent beauty which hath not some strangeness in the proportion" | Francis Bacon |

### Trade-offs and Constraints

| Principle | Description |
|-----------|-------------|
| Fast, cheap, and reliable | choose two | Old engineering proverb |
| Freedom, security, and convenience | choose two | Unknown |
| Law of Diminishing Returns | If one factor of production is increased while the others remain constant, the overall returns will relatively decrease after a certain point | W. J. Spillman and E. Lang (1924) |

## Software Architecture Paradoxes

| Paradox | Description | Source |
|---------|-------------|---------|
| Paradox #1: Flexibility breeds complexity | We aim to design flexible software; yet, in doing so, we see an undesirable increase in complexity | Kirk Knoernschild (2012) |
| Paradox #2: Reuse complicates use | We strive to develop reusable software, only to impair the software's ease of use | Kirk Knoernschild (2012) |
| Paradox #3: Evolution impedes survival | We design a software system that can evolve, but in doing so hasten its death | Kirk Knoernschild (2012) |

## Security and Trust

### Core Security Concepts

| Concept | Description | Source |
|---------|-------------|---------|
| CIA triad | Confidentiality, Integrity, Availability | Famous summary of computer security concerns |
| Trust definition | Trust is the availability of effective recourse | Dan Geer (2014) |
| Security engineering | Security engineering is about tolerable failure modes. Determine which failure modes are tolerable and which are not, and design around not having the intolerable ones | Dan Geer (2014) |
| Shannon's maxim | One ought to design systems under the assumption that the enemy will immediately gain full familiarity with them | - |

## Programming Philosophy

### Code Quality and Design

| Principle | Description | Source |
|-----------|-------------|---------|
| Programs must be written for people to read | and only incidentally for machines to execute | Harold Abelson |
| Any fool can write code that a computer can understand | Good programmers write code that humans can understand | Martin Golding |
| Talk is cheap | Show me the code | Linus Torvalds |
| Design is the art of arranging code | to work today, and be changeable forever | Sandi Metz |

### Problem-Solving Approaches

| Quote | Source |
|-------|---------|
| "Sometimes the problem is to discover what the problem is" | Gordon Glegg, 'The Design of Design' (1969) |
| "The besetting mistake of expert designers is not designing the thing wrong, but designing the wrong thing" | Frederick P. Brooks, 'The Design of Design: Essays from a Computer Scientist' (2010) |
| "All problems in computer science can be solved by another level of indirection, except of course for the problem of too many indirections" | David Wheeler |

## System Design Principles

### Butler W. Lampson's Design Guidelines (1983)

#### Interface Design

| Principle | Description |
|-----------|-------------|
| Do one thing at a time, and do it well | An interface should capture the minimum essentials of an abstraction. Don't generalize; generalizations are generally wrong |
| If in doubt, leave it out | - |
| Keep secrets of the implementation | Secrets are assumptions about an implementation that client programs are not allowed to make |

#### Performance and Optimization

| Principle | Description |
|-----------|-------------|
| Handle normal and worst cases separately | The normal case must be fast. The worst case must make some progress |
| Compute in background when possible | Rapid response is better for users, and there is likely to be idle processor time later |
| Safety first | In allocating resources, strive to avoid disaster rather than to attain an optimum |

#### Key Reminders

| Rule | Description |
|------|-------------|
| Keep it simple | - |
| Interfaces to abstractions | - |
| Write a spec | - |

## Distributed Systems

### Leslie Lamport's Insights

| Quote | Context |
|-------|---------|
| "A distributed system is one where the failure of a machine you've never heard of stops you from getting any work done" | - |
| "Success really depends on the conception of the problem, the design of the system, not in the details of how it's coded" | - |
| "If you're building a complicated system, the battle is won or lost before a single piece of code is written" | - |

### Terry Crowley's Rules of Distributed Systems Design

| Rule | Description |
|------|-------------|
| Rule 1 | Think through the implications to the user experience from the start rather than trying to patch on error handling, cancellation and status reporting as an afterthought |
| Rule 2 | Use asynchronous techniques to couple components. Synchronous coupling is impossible |
| Rule 3 | Recognize and explicitly design for interacting state machines |
| Rule 4 | Failure is expected. The only guaranteed way to detect failure in a distributed system is to simply decide you have waited 'too long' |
| Rule 5 | Cancellation is not rollback since it is just reclaiming local resources and state |
| Rule 6 | You can never really know the state of a distributed component |

## Unix Philosophy

### Mike Garcanz's Unix Philosophy

| Principle | Description |
|-----------|-------------|
| Small is beautiful | - |
| Make each program do one thing well | - |
| Build a prototype as soon as possible | - |
| Choose portability over efficiency | - |
| Store data in flat text files | - |
| Use software leverage to your advantage | - |
| Use shell scripts to increase leverage and portability | - |
| Avoid captive user interfaces | - |
| Make every program a filter | - |

### Doug McIlroy's Unix Principles (1978)

| Principle | Description |
|-----------|-------------|
| Do one thing well | Make each program do one thing well. To do a new job, build afresh rather than complicate old programs by adding new features |
| Expect composition | Expect the output of every program to become the input to another, as yet unknown, program |
| Build early | Design and build software, even operating systems, to be tried early, ideally within weeks |
| Use tools | Use tools in preference to unskilled help to lighten a programming task |

### Unix Wisdom

| Quote | Source |
|-------|---------|
| "Those who don't understand Unix are condemned to reinvent it, poorly" | Henry Spencer |
| "Unix is simple. It just takes a genius to understand its simplicity" | Dennis Ritchie |
| "When in doubt, use brute force" | Ken Thompson |
| "One of my most productive days was throwing away 1000 lines of code" | Ken Thompson |

## Eric S. Raymond's Unix Programming Principles

### Design Principles

| Principle | Description |
|-----------|-------------|
| Modularity | Write simple parts connected by clean interfaces |
| Composition | Design programs to be connected to other programs |
| Separation | Separate policy from mechanism; separate interfaces from engines |
| Parsimony | Write a big program only when it is clear by demonstration that nothing else will do |
| Robustness | Robustness is the child of transparency and simplicity |
| Representation | Fold knowledge into data so program logic can be stupid and robust |

### User Interface Principles

| Principle | Description |
|-----------|-------------|
| Least Surprise | In interface design, always do the least surprising thing |
| Silence | When a program has nothing surprising to say, it should say nothing |
| Repair | When you must fail, fail noisily and as soon as possible |
| Reversibility | Every operation without an undo is a horror story waiting to happen |

## Chinese Wisdom

### Chinese Idioms for Software Development

| Chinese | Pinyin | English Translation | Application |
|---------|--------|-------------------|-------------|
| 不可得兼 | bù kě dé jiān | You can't have both at the same time | Trade-offs |
| 力不从心 | lì bù cóng xīn | Frustrated aspirations | Technical limitations |
| 画蛇添足 | huà shé tiān zú | To draw a snake and add legs | Over-engineering |
| 亡羊补牢 | wáng yáng bǔ láo | Better late than never | Bug fixes |
| 脚踏实地 | jiǎo tà shí dì | Tread on solid ground | Solid foundations |
| 豁然开朗 | huò rán kāi lǎng | Eureka! | Problem-solving moments |

## Data and Performance

### Data-Centric Design

| Quote | Source |
|-------|---------|
| "Design the data, not the code" | Jon Devaan |
| "Bring the computation to the data rather than bringing the data to the computation" | - |
| "When looking at the structure of a system, I'm less interested in seeing how the code interacts... I want to see how the data interacts and flows" | Terry Crowley |

### Performance Insights

| Quote | Source |
|-------|---------|
| "In the time that bandwidth doubles, latency improves by no more than a factor of 1.2 to 1.4" | David Patterson, U.C. Berkeley (2004) |
| "Much of performance analysis is about three things: locality, locality, locality" | Terry Crowley |
| "An efficient program is an exercise in logical brinkmanship" | Edsger Dijkstra |

## Complexity and Simplicity

### Managing Complexity

| Quote | Source |
|-------|---------|
| "Successful programming is all about managing complexity" | Keith Bentley |
| "The unavoidable price of reliability is simplicity. It is a price which the very rich find hard to pay" | Sir C. A. R. ('Tony') Hoare |
| "The most robust programs isolate complexity in a way that lets significant parts of the system appear simple and straightforward" | Terry Crowley |

### Simplicity Principles

| Quote | Source |
|-------|---------|
| "It seems that perfection is reached not when there is nothing left to add, but when there is nothing left to take away" | Antoine de Saint Exupéry |
| "Do more and more with less and less until eventually you can do everything with nothing" | Buckminster Fuller |
| "Keep your code absolutely simple. Keep looking at your functions and figure out how you simplify further" | John Romero, id Software |

## Anti-Patterns and Warnings

### Common Pitfalls

| Anti-Pattern | Description | Source |
|--------------|-------------|---------|
| Inner-platform effect | The tendency to create a system so customizable as to become a replica of the software development platform | - |
| Second system effect | The tendency of small, elegant systems to be succeeded by over-engineered, bloated systems | - |
| RPC fallacy | Making remote/slow/independent things pretend to be local/fast/fate-shared | Wes Felter |

### Humorous Observations

| Quote | Source |
|-------|---------|
| "Some people when faced with a problem think: 'I know, I'll use distributed computing'. Now they have N^2 problems" | @jamesiry |
| "UML - Unnecessary Management Lingo" | @iamdevloper |
| "There are only two hard things in Computer Science: off by one errors, cache invalidation and naming things" | Phil Karlton |

## Philosophical Perspectives

### Ancient Wisdom Applied

| Quote | Source | Context |
|-------|--------|---------|
| "πάντα ῥεῖ (panta rhei): Everything flows" | Heraclitus of Ephesus (~535–475BC) | Change and evolution |
| "The height of cleverness is to be able to conceal it" | Francois de la Rochefoucauld (1613-1680) | Interface design |
| "Lest men suspect your tale untrue, keep probability in view" | John Gay (1727) | System reliability |

### Modern Philosophical Insights

| Quote | Source |
|-------|---------|
| "For every proverb, there is an equal and opposite proverb" | Philip Wadler (2011-03-23) |
| "The only people who see the whole picture, are the ones who step out of the frame" | Salman Rushdie |
| "Human problems remain human problems, and the higher work of computers doesn't erase that" | Andrew O'Hagan |