NDLI: Designing families of data types using exemplars

Content Provider	ACM Digital Library
Author	Lalonde, Wilf R.
Copyright Year	1989
Abstract	Designing data types in isolation is fundamentally different from designing them for integration into communities of data types, especially when inheritance is a fundamental issue. Moreover, we can distinguish between the design of families—integrated types that are variations of each other—and more general communities where totally different but cohesive collections of types support specific applications (e.g., a compiler). We are concerned with the design of integrated families of data types as opposed to individual data types; that is, on the issues that arise when the focus is intermediate between the design of individual data types and more general communities of data types. We argue that design at this level is not adequately served by systems providing only class-based inheritance hierarchies and that systems which additionally provide a coupled subtype specification hierarchy are still not adequate. We propose a system that provides an unlimited number of uncoupled specification hierarchies and illustrate it with three: a subtype hierarchy, a specialization/generalization hierarchy, and a like hierarchy. We also resurrect a relatively unknown Smalltalk design methodology that we call programming-by-exemplars and argue that it is an important addition to a designer's grab bag of techniques. The methodology is used to show that the subtype hierarchy must be decoupled from the inheritance hierarchy, something that other researchers have also suggested. However, we do so in the context of exemplar-based systems to additionally show that they can already support the extensions required without modification and that they lead to a better separation between users and implementers, since classes and exemplars can be related in more flexible ways. We also suggest that class-based systems need the notion of private types if they are to surmount their current limitations. Our points are made in the guise of designing a family of List data types. Among these is a new variety of lists that havenever been previously published: prefix-sharing lists. We also argue that there is a need for familial classes to serve as an intermediary between users and the members of a family.
Starting Page	212
Ending Page	248
Page Count	37
File Format	PDF
ISSN	01640925
e-ISSN	15584593
DOI	10.1145/63264.63265
Volume Number	11
Issue Number	2
Journal	ACM Transactions on Programming Languages and Systems (TOPLAS)
Language	English
Publisher	Association for Computing Machinery (ACM)
Publisher Date	1989-04-01
Publisher Place	New York
Access Restriction	One Nation One Subscription (ONOS)
Content Type	Text
Resource Type	Article
Subject	Software

Sl.	Authority	Responsibilities	Communication Details
1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
2	Indian Institute of Technology Kharagpur	Host Institute of the Project: The host institute of the project is responsible for providing infrastructure support and hosting the project	https://www.iitkgp.ac.in
3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
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