.. -*- coding: utf-8; -*-

============================

 Software development rules

============================

.. contents::

   :local:

General discussion

==================

See:

* http://en.wikipedia.org/wiki/List_of_software_development_philosophies

* http://en.wikipedia.org/wiki/List_of_eponymous_laws

Principle of good enough (POGE)

===============================

It favours quick-and-simple (but potentially extensible) designs over

elaborate systems designed by committees.

Once the quick-and-simple design is deployed, it can then evolve as needed,

driven by user requirements.

This kind of design is not appropriate in systems where it is not possible to

evolve the system over time, or where the full functionality is required from

the start.

See:

* http://en.wikipedia.org/wiki/Principle_of_good_enough

No Silver Bullet

================

There is no single development, in either technology or management technique,

which by itself promises even one order of magnitude improvement within a

decade in productivity, in reliability, in simplicity.

See:

* http://en.wikipedia.org/wiki/No_Silver_Bullet

Rule of thumb

=============

A rule of thumb is a principle that postulate in some case use simple

procedure wich produce approximate result instead use complex but exact

produce.

See:

* http://en.wikipedia.org/wiki/Rule_of_thumb

The Zero One or Infinity

========================

The Zero One or Infinity (ZOI) rule is a rule of thumb in software design. It

suggests that arbitrary limits on the number of instances of a particular

entity should not be allowed. Specifically, that an entity should either be

forbidden entirely, one should be allowed, or any number (presumably, to the

limit of available storage) of them should be allowed. It should not be the

software that puts a hard limit on the number of instances of the entity.

* http://en.wikipedia.org/wiki/Zero_One_Infinity

80-20 rule (pareto principle)

=============================

This rule postulate that roughly 80% of the effects come from 20% of the

causes.

This rule applied to optimisation (most time spent by program only by little

piece of code), functionality (80% of users use only 20% of program

functionality); bugs (fixing the top 20% of most reported bugs solve 80% of

the error and crashes).

See:

* http://en.wikipedia.org/wiki/80:20_rule

1% rule

=======

The 1% rule states that the number of people who create content on the

internet represents approximately 1% (or less) of the people actually viewing

that content.

See:

* http://en.wikipedia.org/wiki/1%25_rule_%28Internet_culture%29

Parkinson's Law

===============

Work expands so as to fill the time available for its completion.

Data expands to fill the space available for storage.

See:

* http://en.wikipedia.org/wiki/Parkinson%27s_law

Ninety-ninety rule

==================

The first 90% of the code accounts for the first 10% of the development time.

The remaining 10% of the code accounts for the other 90% of the development

time.

See:

* http://en.wikipedia.org/wiki/Ninety-ninety_rule

Wirth's law

===========

Software is getting slower more rapidly than hardware becomes faster.

See:

* http://en.wikipedia.org/wiki/Wirth%27s_law

Student syndrome

================

Student syndrome refers to the phenomenon that many people will start to fully

apply themselves to a task just at the last possible moment before a deadline.

The student syndrome is a form of procrastination ().

See:

* http://en.wikipedia.org/wiki/Student_syndrome

Conway's Law

============

...organizations which design systems ... are constrained to produce designs

which are copies of the communication structures of these organizations.

Example: Consider a two-person team of software engineers, A and B. Say A

designs and codes a software class X. Later, the team discovers that class X

needs some new features. If A adds the features, A is likely to simply expand X

to include the new features. If B adds the new features, B may be afraid of

breaking X, and so instead will create a new derived class X2 that inherits X's

features, and puts the new features in X2. So the final design is a reflection

of who implemented the functionality.

A real life example: NASA's Mars Climate Orbiter crashed because one team used

United States customary units (e.g., inches, feet and pounds) while the other

used metric units for a key spacecraft operation.

See:

* http://en.wikipedia.org/wiki/Conway%27s_Law

Brooks's law

============

It takes some time for the people added to a project to become productive.

Communication overheads increase as the number of people increases.

Adding manpower to a late software project makes it later.

See:

* http://en.wikipedia.org/wiki/Brooks%27_law

Code bloat

==========

Code bloat is the production of code that is perceived as unnecessarily long,

slow, or otherwise wasteful of resources. Code bloat generally refers to

source code size but sometimes is used to refer to the generated code size or

even the binary file size.

* http://en.wikipedia.org/wiki/Code_bloat

Software bloat

==============

Software bloat is a term used to describe the tendency of newer computer

programs to have a larger installation footprint, or have many unnecessary

features that are not used by end users, or just generally use more system

resources than necessary, while offering little or no benefit to its users.

Comparison of Microsoft Windows minimum hardware requirements (for 32-bit

versions):

Windows version     Processor   Memory  Hard disk

Windows 95[4]        25 MHz      4 MB    ~50 MB

Windows 98[5]        66 MHz     16 MB   ~200 MB

Windows 2000[6]     133 MHz     32 MB    650 MB

Windows XP[7]       233 MHz     64 MB    1.5 GB

Windows Vista[8]    800 MHz    512 MB     15 GB

Windows 7[9]          1 GHz      1 GB     16 GB

.. epigraph::

  Every program attempts to expand until it can read mail. Those programs which

  cannot so expand are replaced by ones which can.

  -- Jamie Zawinski

Second-system effect

====================

In computing, the second-system effect or sometimes the second-system syndrome

refers to the tendency, when following on from a relatively small, elegant,

and successful system, to design the successor as an elephantine,

feature-laden monstrosity. The term was first used by Fred Brooks in his

classic The Mythical Man-Month.[1] It described the jump from a set of simple

operating systems on the IBM 700/7000 series to OS/360 on the 360 series.

Inner-platform effect

=====================

The inner-platform effect is the tendency of software architects to create a

system so customizable as to become a replica, and often a poor replica, of

the software development platform they are using.

XXX read more http://thedailywtf.com/Articles/The_Inner-Platform_Effect.aspx

* http://en.wikipedia.org/wiki/Inner-platform_effect

Feature creep

=============

Feature creep is the proliferation of features in a product such as computer

software. Extra features go beyond the basic function of the product and so

can result in baroque over-complication, or "featuritis", rather than simple,

elegant design.

* http://en.wikipedia.org/wiki/Feature_creep

Bullet-point engineering

========================

Bullet-point engineering is a software design anti-pattern where developers

use the features of competing software packages as checklists of features to

implement in their own product. These features are often implemented poorly

and haphazardly, without any real design, merely so they can be added to a

bulleted list of features in marketing material. Bullet point engineering

often leads to feature creep and software bloat but may also simply result in

a poorly designed imitative product.

* http://en.wikipedia.org/wiki/Bullet-point_engineering

KISS

====

Keep it simple and stupid, or keep it simple, stupid!

Instruction creep and function creep, two instances of creeping featuritis,

are examples of failure to follow the KISS principle in software development.

* http://en.wikipedia.org/wiki/KISS_principle

Minimalism

==========

In computing, minimalism refers to the application of minimalist philosophies

and principles in hardware and software design and usage.

* http://en.wikipedia.org/wiki/Minimalism_%28computing%29

Unix philosophy

===============

.. epigraph::

  "Do one thing and do it well."

  -- Doug McIlroy

.. epigraph::

   "Write programs that do one thing and do it well. Write programs to work

   together. Write programs to handle text streams, because that is a universal

   interface."

  -- Doug McIlroy

.. epigraph::

   #. You cannot tell where a program is going to spend its time. Bottlenecks

      occur in surprising places, so do not try to second guess and put in a speed

      hack until you've proven that's where the bottleneck is.

   #. Measure. Do not tune for speed until your performance analysis tool tells

      you which part of the code overwhelms the rest.

   #. Fancy algorithms tend to run more slowly on small data sets than simple

      algorithms. They tend to have a large constant factor in O(n) analysis, and

      n is usually small. So don't get fancy unless Rule 2 indicates that n is big

      enough.

   #. Simplify your algorithms and data structures wherever it makes sense because

      fancy algorithms are more difficult to implement without defects. The data

      structures in most programs can be built from array lists, linked lists,

      hash tables, and binary trees.

   #. Data dominates. If you have chosen the right data structures and organized

      things well, the algorithms will almost always be self-evident. Data

      structures, not algorithms, are central to programming.

   -- Pike: Notes on Programming in C.

.. epigraph::

   1. Small is beautiful.

   2. Make each program do one thing well.

   3. Build a prototype as soon as possible.

   4. Choose portability over efficiency.

   5. Store data in flat text files.

   6. Use software leverage to your advantage.

   7. Use shell scripts to increase leverage and portability.

   8. Avoid captive user interfaces.

   9. Make every program a filter.

   -- Mike Gancarz: The UNIX Philosophy

With this not all agree:

1. Allow the user to tailor the environment.

2. Make operating system kernels small and lightweight.

3. Use lowercase and keep it short.

4. Save trees.

5. Silence is golden.

6. Think parallel.

7. The sum of the parts is greater than the whole.

8. Look for the 90-percent solution.

9. Worse is better.

10. Think hierarchically.

Misc

====

"Unix is simple. It just takes a genius to understand its simplicity."

  -– Dennis Ritchie

"Unix never says 'please'."

  -– Rob Pike

* http://en.wikipedia.org/wiki/Unix_philosophy

Worse is better

===============

In the "Worse is better" design style, simplicity of both the interface and

the implementation is more important than any other attribute of the system —

including correctness, consistency and completeness.

Simplicity

  The design must be simple, both in implementation and interface. It is

  more important for the implementation to be simpler than the interface.

  Simplicity is the most important consideration in a design.

Correctness

  The design must be correct in all observable aspects. It is slightly better

  to be simple than correct.

Consistency

  The design must not be overly inconsistent. Consistency can be sacrificed

  for simplicity in some cases, but it is better to drop those parts of the

  design that deal with less common circumstances than to introduce either

  implementational complexity or inconsistency.

Completeness

  The design must cover as many important situations as is practical. All

  reasonably expected cases should be covered. Completeness can be sacrificed

  in favor of any other quality. In fact, completeness must be sacrificed

  whenever implementation simplicity is jeopardized. Consistency can be

  sacrificed to achieve completeness if simplicity is retained; especially

  worthless is consistency of interface.

http://dreamsongs.com/WIB.html

  Lisp: Good News, Bad News, How to Win Big

The right thing

===============

The MIT approach (known as "The right thing"):

Simplicity

  The design must be simple, both in implementation and interface. It is

  more important for the interface to be simpler than the implementation.

Correctness

  The design must be correct in all observable aspects. Incorrectness is

  simply not allowed.

Consistency

  The design must be consistent. A design is allowed to be slightly less

  simple and less complete to avoid inconsistency. Consistency is as important

  as correctness.

Completeness

  The design must cover as many important situations as is practical. All

  reasonably expected cases must be covered. Simplicity is not allowed to

  overly reduce completeness.

See:

http://dreamsongs.com/WIB.html

  Lisp: Good News, Bad News, How to Win Big

YAGNI

=====

"You aren't gonna need it" (or YAGNI for short) is the principle in extreme

programming that programmers should not add functionality until it is

necessary.

* http://en.wikipedia.org/wiki/You_ain%27t_gonna_need_it

DRY (DIE)

=========

Don't Repeat Yourself (DRY) or Duplication is Evil (DIE).

* VCS allow multiple and diverging copies ("branches").

* Source code generation.

* http://en.wikipedia.org/wiki/Don%27t_repeat_yourself

Do it yourself (DIY)

====================

Do it yourself (or DIY) is a term used to describe building, modifying, or

repairing of something without the aid of experts or professionals.

when tasklist longer then people life mutch easy use already written libraries

then wrote own.

* http://en.wikipedia.org/wiki/Do_it_yourself

Once and Only Once (OAOO)

=========================

MoSCoW Method

=============

The capital letters in MoSCoW stand for:

* M - MUST have this (included in the current delivery timebox in order

  for it to be a success).

* S - SHOULD have this if at all possible (critical to the success of the

  project, but are not necessary for delivery in the current delivery

  timebox).

* C - COULD have this if it does not affect anything else (nice to have).

* W - WON'T have this time but WOULD like in the future.

See:

* http://en.wikipedia.org/wiki/MoSCoW_Method

Separation of concerns

======================

In computer science, separation of concerns (SoC) is the process of separating

a computer program into distinct features that overlap in functionality as

little as possible. A concern is any piece of interest or focus in a program.

Typically, concerns are synonymous with features or behaviors. Progress

towards SoC is traditionally achieved through modularity of programming and

encapsulation (or "transparency" of operation), with the help of information

hiding. Layered designs in information systems are also often based on

separation of concerns (e.g., presentation layer, business logic layer, data

access layer, database layer).

HyperText Markup Language (HTML) and cascading style sheets (CSS) are

languages intended to separate style from content.

* http://en.wikipedia.org/wiki/Separation_of_concerns

Modular design

==============

In systems engineering, modular design — or "modularity in design" — is an

approach that subdivides a system into smaller parts (modules) that can be

independently created and then used in different systems to drive multiple

functionalities.

* http://en.wikipedia.org/wiki/Modular_design

Occam's razor

=============

"entia non sunt multiplicanda praeter necessitatem"

Entities must not be multiplied beyond necessity.

Code and fix

============

Programmers immediately begin producing code. Bugs must be fixed before the

product can be shipped.

* http://en.wikipedia.org/wiki/Code_and_fix

Cowboy coding

=============

Cowboy coding is a term used to describe software development where the

developers have autonomy over the development process. This includes control

of the project's schedule, algorithms, tools, and coding style.

A cowboy coder can be a lone developer or part of a group of developers with

either no external management or management that controls only non-development

aspects of the project, such as its nature, scope, and feature set (the

"what", but not the "how").

* http://en.wikipedia.org/wiki/Cowboy_coding

Extreme Programming

===================

* http://en.wikipedia.org/wiki/Extreme_Programming

Hollywood Principle

===================

In computer programming, the Hollywood Principle is stated as "don't call us,

we'll call you." It has applications in software engineering; see also

implicit invocation for a related architectural principle.