R. Motschnig-Pitrik and J. Mylopoulos. Classes and instances. International Journal of Intelligent and Cooperative Information Systems, 1(1):61-92 (1992).  Home/Search   Document Not in Database   Summary   Related Articles   Check

.... are well established mechanisms in object oriented modelling and in conceptual modelling [8, 17, 20, 25] Inheritance typically takes place from classes to instances: a class is a container of information common to its instances and each instance inherits a number of properties by class membership [22]. Specialization hierarchies, on the other hand, allow the organization of classes in a way that a subclass contains only declarations of properties that do not appear in its superclasses. This implies that a class declaration may not contain explicitly all information common to the class ....

....in the model. The In relation between individuals appears in many data models. Our view on instantiation was inspired by Telos [23] where the In relation is applicable not only to individuals but also to arrows. An overview of manifestations of instantiation in several systems is given in [22]. y In the object oriented terminology [17] an instance variable (also called member attribute) of a class c is a property declaration for which instances of c may carry a specific value. A class variable (also called type attribute) of c corresponds to a property of c as a whole, e.g. the ....

R. Motschnig-Pitrik and J. Mylopoulos. Classes and instances. International Journal of Intelligent and Cooperative Information Systems, 1(1):61-92 (1992).

....expressive power and of the associated reasoning capabilities on both unrestricted and nite models, our logic provides a common core for class based representation formalisms. 1. Introduction In many elds of computer science we nd formalisms for the representation of objects and classes (Motschnig Pitrik Mylopoulous, 1992). Generally speaking, an object denotes an element of the domain of interest, and a class denotes a set of objects with common characteristics. We use the term class based representation formalism to refer to a formalism that allows one to express several kinds of relationships and constraints ....

Motschnig-Pitrik, R., & Mylopoulous, J. (1992). Classes and instances. Journal of Intelligent and Cooperative Information Systems, 1 (1).

.... collector Art object Painting collector Painting collects collects collects Only collector painting (a) b) Figure 5: Introducing the RISA relation A class can be seen as a container of information common to its instances, and each instance inherits a number of properties by class membership [22]. However, problems may arise, as several different semantics are possible for the inherited properties. For example, in Figure 5(a) an instance o of Painting collector inherits the property collects of Painting collector by being an instance of this class. However, as o is also instance of Art ....

R. Motschnig-Pitrik, J. Mylopoulos, Classes and Instances, International Journal of Intelligent and Cooperative Information Systems, 1(1), 61-92 (1992).

....in order to define the entities AcmConference and ItalianPaper. The above observations show that several interesting modeling constructs are available in our model, all based on the notion of class, which is generally recognized as the central notion of most of the existing representation models [20]. By carrying out an analysis of the main constructs available in di#erent models, it is possible to show that the most of the data models proposed in the literature are actually subsumed by our model. This is particularly important in our context, where we assume that, in case the cooperative ....

R. Motschnig-Pitrik, J. Mylopolous. "Classes and instances." International Journal of Intelligent and Cooperative Information Systems, 1:1, 1992.

....part relationship. It is defined as a binary relationship and noted as a straight line with a diamond on the side of the composite. For example, Figure 1 (b) shows three part relationships, between components Editorial, Article, Picture, and composite Newspaper More formally, part relationship [8, 13, 16] is a binary relationship, written P r Cpn;Cps , between two classes where Cpn is a component class and Cps a composite class. We also refer to a component class (e.g. Article or Picture in Figure 1(b) as a part class and to a composite class (e.g. Newspaper) as a whole class [8] The part ....

....of methods. Methods are used by instances to send and answer messages. Classes are instances of metaclasses and metaclasses play essentially the same role for classes as classes do for their instances. A metaclass describes the structures and behaviors of classes in term of attributes and methods [16]. Thus, metaclasses open the possibility for the developer to define new types of classes with different structure and behavior in order to tailor them to the needs of the applications. Abstractions, like semantic relationships [12] can be introduced through the definition of metaclasses or ....

R. Motschnig-Pitrik and J. Mylopoulos. Classes and instances. International Journal of Intelligent and Cooperative Information Systems, 1(1):61--92, 1992.

.... collector Painting collects collects Painting (a) b) Figure 4: Differentiation of class semantics through arrow covering First, let us recall that a class can be seen as a container of information common to its instances, and each instance acquires a number of properties by class membership [27]. However, problems may arise, as several different semantics are possible for the acquired properties. For example, in Figure 4(a) an instance o of Painting collector acquires the property collects of Painting collector by being an instance of the class. However, as o is also an instance of Art ....

R. Motschnig-Pitrik, J. Mylopoulos, Classes and Instances, International Journal of Intelligent and Cooperative Information Systems, 1(1), 61-92 (1992).

....ISA is a stronger form of ISA which is defined for arrow classes and expresses property value refinement. In what follows, we motivate its introduction. A class can be seen as a container of information common to its instances, and each instance acquires a number of properties by class membership [29]. However, problems may arise, as several different semantics are possible for the acquired properties. For example, in Figure 2(c) an instance o of Painting collector acquires the property collects of Painting collector by being an instance of the class. However, as o is also an instance of Art ....

R. Motschnig-Pitrik, J. Mylopoulos, Classes and Instances, International Journal of Intelligent and Cooperative Information Systems, 1(1), 61-92 (1992).

....power and of the associated reasoning techniques on both unrestricted and finite models, our language provides a unified framework for class based representation formalisms. 1 INTRODUCTION In many fields of Computer Science we find formalisms for the representation of objects and classes [MM92]. Generally speaking a class denotes a subset of the domain of discourse, and a class based representation formalism allows one to express several kinds of relationships and constraints (e.g. subclass constraints) holding among classes. Moreover, class based formalisms aim at taking advantage of ....

R. Motschnig-Pitrik and J. Mylopoulous. Classes and instances. Journal of Intelligent and Cooperative Inf. Syst., 1(1), 1992.

....classes to Research conducted while this author was visiting with the Institute of Computer Science, Foundation for Research and Technology Hellas. instances: a class is a container of information common to its instances and each instance inherits a number of properties by class membership [22]. Specialization hierarchies, on the other hand, allow to organize classes in a way that a subclass contains only declarations of properties that do not appear in its superclasses. This implies that a class declaration may not contain explicitly all information common to the class instances and ....

....in the model. The In relation between individuals appears in many data models. Our view on instantiation was inspired by Telos [23] where the In relation is applicable not only to individuals but also to arrows. An overview of manifestations of instantiation in several systems is given in [22]. 3.2 Specialization Any two classes in the model can be related through a relation, denoted by Isa. The pairs of classes that are related through this relation are either declared by the user or derived by the system. The declaration of pairs by the user is done under the following assumption: ....

R. Motschnig-Pitrik, J. Mylopoulos, Classes and Instances, International Journal of Intelligent and Cooperative Information Systems, 1(1), 61-92 (1992).

....provide valuable support for the data modeling activity. Generally speaking, a class denotes a subset of the domain of discourse, and a class based representation formalism allows one to express several kinds of relationships and constraints (e.g. subclass constraints) holding among classes [MM92]. Moreover, class based formalisms aim at taking advantage of the class structure in order to provide various information, such as whether an element belongs to a class, whether a class is a subclass of another class, and more generally, whether a given constraint holds among a given set of ....

R. Motschnig-Pitrik and J. Mylopoulous. Classes and instances. Journal of Intelligent and Cooperative Information Systems, 1(1), 1992.

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R. Motschnig-Pitrik, J. Mylopoulos, Classes and Instances, International Journal of Intelligent and Cooperative Information Systems, 1(1), 61-92 (1992).

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