Class (philosophy)

About: Class (philosophy) is a research topic. Over the lifetime, 821 publications have been published within this topic receiving 28000 citations.

Method and system for implementing software objects

Abstract: The present invention provides a new system for implementing software objects using an object-prototype model. Objects are defined as collections of properties, each having a unique property name. A collection of property names defines a 'shape'. The use of shapes frees the representation of an object in memory from the order in which the properties of the object are declared. Methods are defined independently of objects and are applicable to a specified shape, rather than to objects that are derived from a class in which the method is defined. Methods can be applied to any object that has the specified shape or that has a superset of the properties defining the specified shape, regardless of the place of the object in any inheritance hierarchy. The definition of a shape can also include additional selection criteria, such as restrictions on the values of properties, so that the application of a method can be restricted to objects satisfying the specified criteria. The properties of objects can be divided into subgroups representing different aspects of the object and different subgroups of an object can be inherited from different parent objects, based upon either a has-a or an is-a hierarchy. The shape of an object is determined by all of its properties and is not confined by subgroup boundaries.

Classes and Cladists

Abstract: Beatty, J. (Department of the History of Science, Harvard University, Cambridge, Massachusetts 02138) 1982. Classes and cladists. Syst. Zool., 31:25-34.-Disillusions concerning evolutionary theorizing have forced a split among cladists. The disillusioned group of "pattern" cladists seeks an evolutionarily neutral brand of cladistics. But pattern cladistics is not, after all, evolutionarily neutral. Rather, it is at odds with evolutionary theorizing. [Classes; cladistics; evolution; phylogenetics; Popper.] Hull (1976, 1978) has argued that if species are interpreted as classes, as is traditional, then a little problem arisesnamely, species cannot evolve. But according to our best accounts, they do. Thus there is an inconsistency in our understanding of species. In Section 1, I reformulate the difficulty in order to reemphasize the problem. My ultimate purpose, however, is to discuss the differences between two ever more distinguishable groups of cladists in terms of the difficulty that this problem poses for each. In Section 2, I discuss the background to the widening split between phylogenetic and pattern cladists. Finally, in Section 3, I argue that pattern cladism has conceptual drawbacks that stem from the problem outlined in Section 1. 1. Evolutionary Theory vs. a School of Systematics 1.1The sort of interpretation of species that Hull finds most objectionable from the viewpoint of evolutionary biology is one according to which a species name is defined in terms of the set of properties operationally employed to recognize and distinguish members of that.species from other species. Thus, we recognize and distinguish polar bears (Ursus maritimus) from brown bears (Ursus arctos) by, among other traits, their white coats. Consequently, we might include the differentiating property "white coat" in the definition of "Ursus maritimus." We would also include the other properties that distinguish maritimus from other species of Ursus, as well as those properties that distinguish Ursus from other genera of its family, and the properties that distinguish its family from other families of its order, and so on. To say that species so designated are "classes" is just to say that they are collections of objects that share the defining properties of the species name. Two kinds of classes, hence two kinds of class interpretations of species, are commonly distinguished (e.g., Beckner, 1959, Chapter 5; Caplan, 1980). The name of an "Aristotelian class" is defined in terms of properties that are collectively necessary and sufficient for membership in the group. Members of a "cluster class," on the other hand, need only satisfy most of the defining properties of the class name. So any defining property of the name of an Aristotelian class is present in 100% of the members of that class, while any defining property of a cluster class is present in a high proportion of members of the class. One can imagine still other sorts of class interpretations of species. For example, the defining properties of a species name need not be the usual sorts of properties operationally used to recognize and distinguish members of different species. They might instead be relational properties like interbreeding and ancestor-descendant relations specified with regard to model members of the group. Alternative class interpretations like the latter can be worked out. But it is the interpretation in terms of the usual recognition properties that is at issue in Hull's work and in the recent division

Heegaard splittings of branched coverings of

Abstract: This paper concerns itself with the relationship between two seemingly different methods for representing a closed, orientable 3-manifold: on the one hand as a Heegaard splitting, and on the other hand as a branched covering of the 3-sphere. The ability to pass back and forth between these two representations will be applied in several different ways: 1. It will be established that there is an effective algorithm to decide whether a 3-manifold of Heegaard genus 2 is a 3-sphere. 2. We will show that the natural map from 6-plat representations of knots and links to genus 2 closed oriented 3-manifolds is injective and surjective. This relates the question of whether or not Heegaard splittings of closed, oriented 3manifolds are "unique" to the question of whether plat representations of knots and links are "unique". 3. We will give a counterexample to a conjecture (unpublished) of W. Haken, which would have implied that S3 could be identified (in the class of all simply-connected 3-manifolds) by the property that certain canonical presentations for iriS3 are always "nice". The final section of the paper studies a special class of genus 2 Heegaard splittings: the 2-fold covers of S3 which are branched over closed 3-braids. It is established that no counterexamples to the "genus 2 Poincare conjecture" occur in this class of 3-manifolds.

Object-oriented system having object models containing plural objects with instantiation following static classification by class relationships, dynamic classification by temporal instantiation, and causality restrictions

Abstract: An object-oriented data processing system performs a desired processing based upon an object model including a plurality of objects each formed of data and methods. The data processing system includes an external definition that identifies the object and including an identifier for identifying the object, an internal definition for carrying out a procedure of the object and including an identifier corresponding to the identifier in the external definition, a model classification function for classifying the object model, based upon the external definition, into a static model that indicates a relationship between classes, and a dynamic model that indicates the time sequential relationship between instances forming the classes as a session, a causality restriction function that imposes a causality existing between the static model and the dynamic model, to the static model, a class generation function for creating the classes by combining existing and/or newly created methods; and an instance generation function for creating the instances in correspondence to each of the classes, wherein the class includes a composite class formed of a plurality of classes.