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Schemes: A High Level Data Structuring Concept

IP.com Disclosure Number: IPCOM000128904D
Original Publication Date: 1977-Jan-01
Included in the Prior Art Database: 2005-Sep-20
Document File: 12 page(s) / 45K

Publishing Venue

Software Patent Institute

Related People

James G. Mitchell: AUTHOR [+4]

Abstract

A fundamental aspect of the structure of material contained within a large, intelligent memory system is that the contexts in which units of the stored information are accessed are critically important in determining how that information is interpreted and used. There are numerous proposals for the representation of information within memory. Most of the schemes currently under active consideration can be viewed as variants of list structures or semantic network structures. All these proposals have a number of common features, including context-independent linkage between units, and separation of processing and data elements. In this paper we propose a different form for the representation of information which embodies the opposite assumptions about linkage and the separation of data and process. We examine some implications of these memory structures with respect to how the connections among different memory units are formed and interpreted, and we examine some of the issues of processing that arise when these memory structures are used. The form of our structures is an amalgamation of the principles from the literature on semantic networks, (for example, Norman, Rumelhart, & LNR, 1975; Quillian, 1969) the literature on actors (Hewitt, Bishop, & Steiger, 1974; Kay, 1974) and the new ideas on ";frames"; (Minsky, 1975; Winograd, 1975). We call our structures schemata to emphasize that they differ somewhat from any existing proposals. The word ";schema"; is taken from the psychological literature, where it has had a long history, most commonly associated with the work on memory by Bartlett (1932), and by Piaget. We propose that one schema refers to another only through use of a description which is dependent on the context of the original reference. We also propose that these schemata are active processing elements which can be activated from higher level purposes and expectations, or from input data which must be accounted for.

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THIS DOCUMENT IS AN APPROXIMATE REPRESENTATION OF THE ORIGINAL.

©; Xerox Palo Alto Research Center, January, 1977

Schemes: A High Level Data Structuring Concept

by James G. Mitchell, Ben Wegbreit

CSL-77- 1 January 1977

In recent years, programming languages have provided better constructs for data type definitions and have placed increasing reliance on type machinery for protection, modularization, and abstraction. This paper introduces several new constructs which further these ends. Types may be defined as similar to existing types. extended by additional properties. Schemes are type-parameterized definitions. For example, symbol tables and symbol table operations can be defined as a scheme with the key and value types as parameters; an instantiated of the scheme implements a specific type of symbol table. Because new types are typically defined along with other related types, an instantiated scheme may export a set of new types. A set of schemes with a common name and common external behavior can be viewed as alternative implementations of an abstraction. Parameter specifications associated with each scheme are used to select the appropriate implementation for each use.

Key Words and Phrases: data types, schemes, polymorphism, programming languages, abstractions CR Categories:
4.12, 4.13, 4.22

XEROX
PALO ALTO RESEARCH CENTER 3333 Coyote Hill Road / Palo Alto / California 94304 TABLE OF CONTENTS

I.Introduction.....1
II.Memory Access Using Descriptions.....2
A. Context-dependent descriptions.....3
B. The form of a description.....5
C. Properties of context-dependent descriptions.....6
III. Processing Structures.....8
A. Basic processing principles.....10
B. Data-limited and resource-limited processes.....11
C. Event driven schemata.....13
D. Depth of processing.....15
E. The organization of processing.....16
IV. Summary.....19
References.....22

I. INTRODUCTION

A fundamental aspect of the structure of material contained within a large, intelligent memory system is that the contexts in which units of the stored information are accessed are critically important in determining how that information is interpreted and used. There are numerous proposals for the representation of information within memory. Most of the schemes currently under active consideration can be viewed as variants of list structures or semantic network

Xerox Corporation Page 1 Jan 01, 1977

Page 2 of 12

Schemes: A High Level Data Structuring Concept

structures. All these proposals have a number of common features, including context- independent linkage between units, and separation of processing and data elements. In this paper we propose a different form for the representation of information which embodies the opposite assumptions about linkage and the separation of data and process. We examine some implications of these memory structures with respect to how the connections among different memory units are formed and interpreted, and we examine some of the issues...