Observer

E173618

behavioral design pattern design pattern

Observer is a behavioral design pattern that defines a one-to-many dependency between objects so that when one object changes state, all its dependents are automatically notified and updated.

Try in SPARQL Jump to: Surface forms Disambiguation Statements Elicitation Referenced by

All labels observed (3)

Label	Occurrences
IObserver	1
Observable	1
Observer canonical	1

How this entity was disambiguated

This entity first appeared as the object of triple T1531331 — resolving that mention is where its identity was fixed. The disambiguator weighed these candidate entities and picked the highlighted one (or “None”, minting a new entity). This is how homonymy is resolved: the same surface form can point to different entities.

NED1 Entity disambiguation (via context triple) gpt-5-mini-2025-08-07

Target entity: Observer
Context triple: [Design Patterns: Elements of Reusable Object-Oriented Software, describesPattern, Observer]

A. Voyeur
"Voyeur" is a 1981 synth-driven pop song by American singer Kim Carnes, known for its dark, edgy style and follow-up success to her hit "Bette Davis Eyes."
B. The New Observer
The New Observer was the original name of the British newspaper that later became known as The Sunday Times.
C. Wanderer
Wanderer is Sterling Hayden’s autobiographical memoir, renowned for its candid reflections on his Hollywood career, seafaring life, and political disillusionment.
D. Storyteller
"Storyteller" is a seminal work of the Native American Renaissance that blends traditional Indigenous oral narratives with contemporary literary forms to explore Native identity and cultural continuity.
E. Beschermer
Beschermer was a Dutch warship that served in the late 18th century and was captured by the British Royal Navy during the Battle of Camperdown in 1797.
F. None of above. chosen
G. Unsure - the case is ambiguous/there is not enough information to decide.

NED2 Entity disambiguation (via description) gpt-5-mini-2025-08-07

Target entity: Observer
Target entity description: Observer is a behavioral design pattern that defines a one-to-many dependency between objects so that when one object changes state, all its dependents are automatically notified and updated.

A. Voyeur
"Voyeur" is a 1981 synth-driven pop song by American singer Kim Carnes, known for its dark, edgy style and follow-up success to her hit "Bette Davis Eyes."
B. The New Observer
The New Observer was the original name of the British newspaper that later became known as The Sunday Times.
C. Wanderer
Wanderer is Sterling Hayden’s autobiographical memoir, renowned for its candid reflections on his Hollywood career, seafaring life, and political disillusionment.
D. Storyteller
"Storyteller" is a seminal work of the Native American Renaissance that blends traditional Indigenous oral narratives with contemporary literary forms to explore Native identity and cultural continuity.
E. Beschermer
Beschermer was a Dutch warship that served in the late 18th century and was captured by the British Royal Navy during the Battle of Camperdown in 1797.
F. None of above. chosen

Statements (48)

Predicate	Object
instanceOf	behavioral design pattern ⓘ design pattern ⓘ
advantage	facilitates reuse of subjects and observers independently ⓘ subject does not need to know concrete observer classes ⓘ supports dynamic registration and removal of observers ⓘ
alternativeName	Dependents pattern ⓘ Listener pattern ⓘ linked to: NSNotificationCenter Publish–Subscribe pattern ⓘ
appearsIn	Design Patterns: Elements of Reusable Object-Oriented Software ⓘ
belongsTo	Gang of Four design patterns ⓘ linked to: Gang of Four design pattern
commonIn	.NET event and delegate model ⓘ GUI frameworks ⓘ Java event model ⓘ reactive programming libraries ⓘ
defines	one-to-many dependency between objects ⓘ
definesResponsibility	Observer updates in response to notifications ⓘ Subject maintains list of observers ⓘ Subject notifies observers of state changes ⓘ
describedBy	Erich Gamma ⓘ John Vlissides ⓘ Ralph Johnson ⓘ Richard Helm ⓘ
disadvantage	can cause cascading updates and performance issues ⓘ can lead to many spurious updates ⓘ notification order may be undefined ⓘ
formalDefinition	defines a one-to-many dependency so that when one object changes state, all its dependents are notified and updated automatically ⓘ
involvesRole	ConcreteObserver ⓘ ConcreteSubject ⓘ Observer ⓘ Subject ⓘ
keyOperation	attach observer ⓘ detach observer ⓘ notify observers ⓘ
purpose	to notify dependents automatically when subject state changes ⓘ
relatedTo	Mediator pattern ⓘ Model–View–Controller architectural pattern ⓘ linked to: Model-View-Controller Singleton pattern ⓘ
supports	broadcast communication ⓘ event-driven programming ⓘ loose coupling between subject and observers ⓘ model–view separation ⓘ
typicalImplementationDetail	observers register via an interface ⓘ subject calls update method on observers ⓘ subject keeps a collection of observer references ⓘ
usedFor	implementing data binding ⓘ implementing event listeners in GUIs ⓘ implementing model–view–controller (MVC) ⓘ notification systems ⓘ

How these facts were elicited

Referenced by (3)

Full triples — surface form annotated when it differs from this entity's canonical label.

Design Patterns: Elements of Reusable Object-Oriented Software → describesPattern → Observer ⓘ

Rx.NET → primaryAbstraction → IObserver ⓘ

linked to: Observer

RxJava → coreConcept → Observable ⓘ