DEV475 Mastering Object-Oriented Analysis and Design with UML ...

DEV475 Mastering Object-Oriented Analysis and Design with UMLWhat Is Hierarchy?What Is Hierarchy?IncreasingabstractionAssetBankAccountSecurityRealEstateSavingsCheckingStockBondDecreasingabstractionElements at the same level of the hierarchyshould be at the same level of abstraction.Mastering Object Oriented Analysis and Design with UMLCopyright © 2003 Rational Software, all rights reserved 22Hierarchy can be defined as:Any ranking or ordering of abstractions into a tree-like structure. Kinds: Aggregationhierarchy, class hierarchy, containment hierarchy, inheritance hierarchy, partitionhierarchy, specialization hierarchy, type hierarchy. (Dictionary of Object Technology,Firesmith, Eykholt, 1995)• Hierarchy organizes items in a particular order or rank (for example, complexityand responsibility). This organization is dependent on perspective. Using ahierarchy to describe differences or variations of a particular concept provides formore descriptive and cohesive abstractions and a better allocation ofresponsibility.• In any one system, there may be multiple abstraction hierarchies (for example, afinancial application may have different types of customers and accounts).• Hierarchy is not an organizational chart or a functional decomposition.• Hierarchy is a taxonomic organization. The use of hierarchy makes it easy torecognize similarities and differences. For example, botany organizes plants intofamilies. Chemistry organizes elements in a periodic table.2 - 22