In this article above we see the clear difference between aggregation and composition with examples. Aggregation. Both association and composition are kind of "has-a" relationships. Composition is a powerful form of “is part of” relationship collated to aggregation “Has-A”. Compositions are a critical building block of many basic data structures. Relationship . They are more specific versions of an association. The diamond end goes on the side of the container . Composition (mixture) is a way to wrap simple objects or data types into a single unit. An aggregation is used when life of object is independent of container object. In a UML diagram, both Aggregation and Composition are represented with a diamond arrow between the classes. Aggregation and Composition Notations represent a special type of association called 'aggregation' between a pair of parent and child classes, where the child … Key Composition Aggregation; 1. In Aggregation , parent Has-A relationship with child entity The only logical difference is aggregation is a weaker relationship. Composition(mixture) is a way to combine simple objects or data types into more complex ones. Aggregation uses an open diamond Despite these similarities, there is a difference between aggregations and compositions. Sr. No. Aggregation (collection) differs from ordinary composition in that it does not imply ownership. Basic . Aggregation is a kind of association that specifies a whole/part relationship between the aggregate (whole) and component part. The composition is the most specific type of aggregation that implies ownership. Aggregation vs composition Summary. Introduction to UML Aggregation vs Composition Many varied types of notation are used in XML to represent association, composition, and aggregation. In composition , parent entity owns child entity. In composition, when the owning object is destroyed, so are the contained objects. Aggregation and Composition are a special type of association and differ only in the weight of the relationship. UML Symbol: Aggregation is denoted by a diamond. Composition in UML. In UML Class Diagrams, both "aggregation" and "composition" have been defined as special cases of associations representing part-whole relationships (which have been discussed in philosophy for a long time). An aggregation and a composition are both a type of association in UML diagrams. Deletion of assembly has no effect in aggregation whereas deletion of the composition can effect in the composition; Conclusion. And in In UML diagram Association is denoted by a normal arrow head. This section describes Aggregation and Composition Notations used in a UML Class Diagram. 2. Functionality Aggregation vs. An association connects two classes that need to communicate somehow. Class A contains Class B, or Class A has an instance of Class B. Aggregation. In UML aggregation can be defined by using line segment whereas In UML composition can be defined by using diamond. But still container object owns the aggregated object. Here association is represented by a simple arrow whereas the aggregation is denoted by a null diamond headed arrow and a full diamond headed arrow is used to represent the composition. March 10, 2011 bujunjie Leave a comment Go to comments. 2. Aggregation vs Composition & Association Aggregation and Composition are subsets of association, meaning they are specific cases of association . Aggregation vs Composition: Aggregation is an association between two objects which describes the “has a” relationship. Composition is denoted by a highlighted diamond. Therefore, UML representations are also very similar. Aggregation is very similar to composition. 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