Java Software Development Unit 3

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abstract class	A class which cannot be instantiated, i.e. one which has no instances of its own but only instances of its child classes. An abstract class deﬁnes properties which are common to its child classes. It should not be confused with a class representing abstract entities.
abstract entity	An entity that has an existence, but does not correspond to a tangible entity. For example, the ﬁlm Citizen Kane is an abstract entity, while the DVD which records the ﬁlm is a tangible entity.
association	An association represents the links that may exist between the objects of two classes. These links have a common meaning, and represent a particular relationship (connection) between these objects that is signiﬁcant for the system domain.
attribute	An attribute is a property of an object. All objects of a class have the same attributes.
candidate class	A class that may be needed to model a category of real-world entities from the system domain.
child class	A class that is a specialisation of some other class, known as its parent class; a subclass.
class (in the conceptual model)	A class models a category of real-world entities from the system domain.
class description	A formal description of a class within a conceptual model or a structural model.
class diagram	Class diagrams are used to show structural aspects of the system domain and of a system at various stages in its development. As a model of the system domain, a class diagram depicts conceptual classes and associations connecting them. As a model of the system, a class diagram depicts the software classes that are involved in the system and the associations connecting them.
conceptual model	The model which represents the signiﬁcant entities in the system domain and the connections between them as a collection of classes and their attributes, associations and invariants. The conceptual model of the system domain is taken to be the initial structural model for the software system to be developed. It consists of a class diagram, class descriptions and invariants.
concrete class	A class that, unlike an abstract class, may have instances that are not instances of any of its child classes.
constraint (on the system domain)	A limitation on the entities in the system domain, their properties and relationships.
derived association	An association all of whose links can be derived using other elements of the model.
derived attribute	An attribute all of whose values can be derived using other elements of the model.
event (in the system domain)	Any signiﬁcant circumstance, episode, interaction, happening or incident, e.g. deliveries, registrations, bookings, enrolments
generalisation	A relationship between classes that captures the similarities and differences between two related classes. Saying that class A is a generalisation of class B means that the common (similar) structure and behaviour is deﬁned by class A, and the distinctive (different) structure and behaviour is deﬁned by class B. It means that an instance of class B is substitutable for an instance of class A.
inherit	Take on the properties (attributes and associations) of a parent class.
initial structural model	The initial structural model is the conceptual model viewed as the ﬁrst model of the structure of the proposed software system. In other words, the conceptual and initial structural models ‘look’ the same but have different perspectives: one models the system domain; the other is taken as the ﬁrst model of the software system itself.
instance	Refers to a particular object of a class or a particular link of an association
invariant	Any condition on the objects of a conceptual model, their attribute values and links that must hold for the requirements to be satisﬁed and the consistency of the model to be guaranteed.
link	A link exists between two objects when there is a connection between the entities they represent that is signiﬁcant for the system domain. A link is an instance of an association.
multiplicity	The multiplicity of an association with respect to one of the classes involved deﬁnes how many objects of that class may be linked with a single object of the other class involved in the association.
noun phrase	A noun phrase is a phrase (a sequence of words like ‘number of copies’) that functions as a noun and which can be used anywhere that a noun could be used.
object (in the conceptual model)	An object models a real-world entity from the system domain.
organisational unit	Any part of an organisational structure to which people or things in the system domain belong.
parent class	A class that is a generalisation of one or more other classes known as its child classes; a superclass.
role	The particular responsibility or job that a person (thing) may perform in the system domain, e.g. employee, student, lecturer, driver.
specialisation	Saying that a class B is a specialisation of class A means that class A is a generalisation of class B.
stereotype	A label providing additional information about some component of a UML model. Stereotypes are enclosed in double chevrons, e.g. <<abstract>>.
structural model	A representation of the system in terms of classes and the relationships between them.
substitutable, substitutability	Objects of a class B are substitutable for objects of a class A if anywhere that an instance of class A is required, an instance of class B can be used instead. For class A to be a generalisation of class B, instances of B must be substitutable for instances of A.
tangible entity	A physical ‘thing’ in the system domain such as an aeroplane, vehicle, reactor or person, i.e. something that can be seen or touched.
value (of an attribute)	Speciﬁc information that an object holds in respect of an attribute.

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Java Software Development Unit 3

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