what is a called that represents the most general entity in an

what is a class called that represents the most general entity in an

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Phrases equivalent to superclass, subclass, or inheritance come to thoughts when serious about the object-oriented method. These ideas are essential when coping with object-oriented programming languages equivalent to Java, Smalltalk, or C++. For modeling courses that illustrate technical ideas they’re secondary. The explanation for that is that modeling related objects or concepts from the true world provides little alternative for utilizing inheritance (examine the category diagram of our case research). Nonetheless, we wish to additional introduce these phrases at this level in Determine 4.26:

Determine 4.26 Notation of generalization

Generalization is the method of extracting shared traits from two or extra courses, and mixing them right into a generalized superclass. Shared traits will be attributes, associations, or strategies.

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In Determine 4.27, the courses Piece of Baggage (1) and Piece of Cargo (2) partially share the identical attributes. From a website perspective, the 2 courses are additionally very related. Throughout generalization, the shared traits (3) are mixed and used to create a brand new superclass Freight (4). Piece of Baggage (5) and Piece of Cargo (6) change into subclasses of the category Freight.

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The shared attributes (3) are solely listed within the superclass, but additionally apply to the 2 subclasses, though they aren’t listed there.

Determine 4.27 Instance of generalization

Contemplate whether or not a number of the courses that you simply discovered might be generalized.

In distinction to generalization, specialization means creating new subclasses from an present class. If it seems that sure attributes, associations, or strategies solely apply to a number of the objects of the category, a subclass will be created. Essentially the most inclusive class in a generalization/specialization is named the superclass and is usually situated on the high of the diagram. The extra particular courses are referred to as subclasses and are usually positioned under the superclass.

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In Determine 4.28, the category Freight (1) has the attribute Diploma of Hazardousness (2), which is required just for cargo, however not for passenger baggage. Moreover (not seen in Determine 4.28), solely passenger baggage has a connection to a coupon. Clearly, right here two related however completely different area ideas are mixed into one class. By way of specialization the 2 particular circumstances of freights are fashioned: Piece of Cargo (3) and Piece of Baggage (4). The attribute Diploma of Hazardousness (5) is positioned the place it belongs—in Piece of Cargo. The attributes of the category Freight (1) additionally apply to the 2 subclasses Piece of Cargo (3) and Piece of Baggage (4):

Determine 4.28 Instance of specialization

Contemplate whether or not a number of the courses that you simply discovered might be specialised.

A lot for the mechanism. Nevertheless, the area which means of the connection between superclass and subclass is way more vital. These guidelines apply to this relationship:

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  • All statements which can be made a couple of superclass additionally apply to all subclasses. We are saying that subclasses “inherit” attributes, associations, and operations from the superclass. For instance: If the superclass Freight has an attribute Weight, then the subclass piece of bags additionally has an attribute Weight, though this attribute shouldn’t be listed within the subclass Piece of Baggage.
  • Something that may be accomplished with an object of the superclass may also be accomplished with an object of the subclass. For instance: If freight will be loaded, items of bags may also be loaded.
  • Within the terminology of the system that’s being modeled, a subclass needs to be a particular type of the superclass. For instance: A bit of bags is a particular case of freight. The counter-example to that is: A flight shouldn’t be a particular case of a flight quantity.