Anti-pattern

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In software engineering, an anti-pattern (or antipattern) is a design pattern that appears obvious but is ineffective or far from optimal in practice.

The term was coined in 1995 by Andrew Koenig, inspired by Gang of Four's book Design Patterns, which developed the concept of design patterns in the software field. The term was widely popularized three years later by the book AntiPatterns, which extended the use of the term beyond the field of software design and into general social interaction. According to the authors of the latter, there must be at least two key elements present to formally distinguish an actual anti-pattern from a simple bad habit, bad practice, or bad idea:

Some repeated pattern of action, process or structure that initially appears to be beneficial, but ultimately produces more bad consequences than beneficial results, and
A refactored solution that is clearly documented, proven in actual practice and repeatable.

Often pejoratively named with clever oxymoronic neologisms, many anti-pattern ideas amount to little more than mistakes, rants, unsolvable problems, or bad practices to be avoided if possible. Sometimes called pitfalls or dark patterns, this informal use of the term has come to refer to classes of commonly reinvented bad solutions to problems. Thus, many candidate anti-patterns under debate would not be formally considered anti-patterns.

By formally describing repeated mistakes, one can recognize the forces that lead to their repetition and learn how others have refactored themselves out of these broken patterns.

Known anti-patterns

Organizational anti-patterns

Analysis paralysis: Devoting disproportionate effort to the analysis phase of a project
Cash cow: A profitable legacy product that often leads to complacency about new products
Cost migration: Transfer of project expenses to a vulnerable department or business partner
Crisis mode (a.k.a firefighting mode): Dealing with things only when they become a crisis, with the result that everything becomes a crisis
Design by committee: The result of having many contributors to a design, but no unifying vision
Escalation of commitment: Failing to revoke a decision when it proves wrong
Management by neglect: Too much delegation
Management by numbers: Paying excessive attention to quantitative management criteria, when these are non-essential or cost too much to acquire
Management by perkele: Authoritarian style of management with no tolerance for dissent
Management by wondering: Expecting a team to define their own objectives, and then wondering what they're doing
Milk Monitor Promotion: A pseudo promotion (a better sounding title), with no additional responsibilities or pay increase, which is given as a quick and costless way to make the employee work harder.
Moral hazard: Insulating a decision-maker from the consequences of his or her decision.
Mushroom management: Keeping employees uninformed and misinformed (kept in the dark and fed manure)
Stovepipe: A structure that supports mostly up-down flow of data but inhibits cross organizational communication
Vendor lock-in: Making a system excessively dependent on an externally supplied component
Violin string organization: A highly tuned and trimmed organization with no flexibility

Project management anti-patterns

Death march: Everyone knows that the project is going to be a disaster - except the CEO. However, the truth remains hidden and the project is artificially kept alive until the Day Zero finally comes ("Big Bang")
Smoke and mirrors: Demonstrating how unimplemented functions will appear
Software bloat: Allowing successive versions of a system to demand ever more resources

Analysis anti-patterns

Napkin specification: The Functional/Technical specification is given to the Development team on a napkin (i.e., informally, and with insufficient detail) which is fundamentally equivalent to having no specification at all.
Phony requirements: All requirements are communicated to the development teams in a rapid succession of netmeeting sessions or phone calls with no Functional/Technical specification or other supporting documentation.
Retro-specification: To write the Technical/Functional specification after the project has already gone live.

Software design anti-patterns

Abstraction inversion: Not exposing implemented functionality required by users, so that they re-implement it using higher level functions
Ambiguous viewpoint: Presenting a model (usually OOAD) without specifying its viewpoint
Big ball of mud: A system with no recognizable structure
Blob: Generalization of God object from object-oriented design
Gas factory: An unnecessarily complex design
Input kludge: Failing to specify and implement handling of possibly invalid input
Interface bloat: Making an interface so powerful that it is extremely difficult to implement
Magic pushbutton: Coding implementation logic directly within interface code, without using abstraction.
Race hazard: Failing to see the consequence of different orders of events
Railroaded solution: A proposed solution that while poor, is the only one available due to poor foresight and inflexibility in other areas of the design
Re-coupling: Introducing unnecessary object dependency
Stovepipe system: A barely maintainable assemblage of ill-related components
Staralised schema: A database schema containing dual purpose tables for normalised and datamart use

Object-oriented design anti-patterns

Anemic Domain Model: The use of domain model without any business logic which is not OOP because each object should have both attributes and behaviors
BaseBean: Inheriting functionality from a utility class rather than delegating to it
Call super: Requiring subclasses to call a superclass's overridden method
Circle-ellipse problem: Subtyping variable-types on the basis of value-subtypes
Empty subclass failure: Creating a class that fails the " Empty Subclass Test" by behaving differently from a class derived from it without modifications
God object: Concentrating too many functions in a single part of the design (class)
Object cesspool: Reusing objects whose state does not conform to the (possibly implicit) contract for re-use
Object orgy: Failing to properly encapsulate objects permitting unrestricted access to their internals
Poltergeists: Objects whose sole purpose is to pass information to another object
Sequential coupling: A class that requires its methods to be called in a particular order
Singletonitis: The overuse of the singleton pattern
Yet Another Useless Layer: Adding unnecessary layers to a program, library or framework. This became popular after the first book on programming patterns.
Yo-yo problem: A structure (e.g., of inheritance) that is hard to understand due to excessive fragmentation

Programming anti-patterns

Accidental complexity: Introducing unnecessary complexity into a solution
Accumulate and fire: Setting parameters for subroutines in a collection of global variables
Action at a distance: Unexpected interaction between widely separated parts of a system
Blind faith: Lack of checking of (a) the correctness of a bug fix or (b) the result of a subroutine
Boat anchor: Retaining a part of a system that no longer has any use
Bug magnet: A block of code so infrequently invoked/tested that it will most likely fail, or any error-prone construct or practice.
Busy spin: Consuming CPU while waiting for something to happen, usually by repeated checking instead of proper messaging
Caching failure: Forgetting to reset an error flag when an error has been corrected
Cargo cult programming: Using patterns and methods without understanding why
Checking type instead of interface: Checking that an object has a specific type when only a certain contract is required. May cause Empty subclass failure.
Code momentum: Over-constraining part of a system by repeatedly assuming things about it in other parts
Coding by exception: Adding new code to handle each special case as it is recognized
Error hiding: Catching an error message before it can be shown to the user and either showing nothing or showing a meaningless message
Expection handling: (From Exception + Expect) Using a language's error handling system to implement normal program logic
Hard code: Embedding assumptions about the environment of a system at many points in its implementation
Lava flow: Retaining undesirable (redundant or low-quality) code because removing it is too expensive or has unpredictable consequences
Loop-switch sequence: Encoding a set of sequential steps using a loop over a switch statement
Magic numbers: Including unexplained numbers in algorithms
Magic strings: Including literal strings in code, for comparisons, as event types etc.
Monkey work: Term for any general repeated support code required within projects which suffer from poor code reuse and design. Is often avoided and rushed, hence open to errors and can quickly become a Bug magnet.
Packratting: Consuming excessive memory by keeping dynamically allocated objects alive for longer than they are needed
Parallel protectionism: When code becomes so complex and fragile that it is easier to clone a parallel infrastructure than to add a trivial attribute to existing infrastructure
Ravioli code: Systems with lots of objects that are loosely connected
Soft code: Storing business logic in configuration files rather than source code
Spaghetti code: Systems whose structure is barely comprehensible, especially because of misuse of code structures
Wrapping wool in cotton: Commonly observed when framework methods are contained in single line methods in wrapper classes which provide no useful abstraction

Methodological anti-patterns

Copy and paste programming: Copying (and modifying) existing code rather than creating generic solutions
De-factoring: The process of removing functionality and replacing it with documentation
Golden hammer: Assuming that a favorite solution is universally applicable (See: Silver Bullet)
Improbability factor: Assuming that it is improbable that a known error will occur
Low hanging fruit: Dealing with easier issues first while ignoring larger more complex issues. It can be thought of as to the relative ease with which scientific, philosophical and technological discoveries are made at first compared with the difficulties once the subject has already been explored.
Not built here : See: Reinventing the wheel, Not invented here.
Premature optimization: Coding early-on for perceived efficiency, sacrificing good design, maintainability, and sometimes even real-world efficiency
Programming by permutation (or "Programming by accident"): Trying to approach a solution by successively modifying the code to see if it works
Reinventing the square wheel: Creating a poor solution when a good one exists
Reinventing the wheel: Failing to adopt an existing, adequate solution
Silver bullet: Assuming that a favorite technical solution can solve a larger process or problem
Tester driven development: Software projects where new requirements are specified in bug reports

Testing anti-patterns

Hostile testing: Antagonizing practical development solutions and workflow with over-testing procedures or over-scheduling test runs
Meta-testing: Overdesigning testing procedures until it is necessary to test them, also known as "watchmen's watchmen"
Moving target: Continuously change design and/or implementation in order to escape established testing procedures

Configuration management anti-patterns

Dependency hell: Problems with versions of required products
Classpath hell: Problems related to specifying Java libraries, their dependencies and their required version to run the application
Extension conflict: Problems with different extensions to pre-Mac OS X versions of the Mac OS attempting to patch the same parts of the operating system
DLL hell: Overutilization of the dynamic-link libraries (DLLs), specifically on Microsoft Windows
JAR hell: Overutilization of the multiple JAR files, usually causing versioning and location problems because of misunderstanding of the Java class loading model

References

External links

Anti-pattern at WikiWikiWeb
Anti-patterns catalog at WikiWikiWeb
AntiPatterns.com Web site for the AntiPatterns book
AntiPatterns Reference
Patterns of Toxic Behavior

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Last updated on Monday July 21, 2008 at 21:41:25 PDT (GMT -0700)
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