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IDL DESIGN: Design Documentation

Page Numbers: Yes X: 527 Y: 10.5"

XEROX Palo Alto Research Center9 February 1977
Inter-Office Memorandum

ToIDL GroupFromBeau Sheil

File<IDL>Design.DocumentationIDL Design Note Number: 1

Subject Design Documentation System

This document describes the initial set of design memos for the IDL project and the method by which that set is to be extended to comprise the specifications for the INTERLISP version of IDL.

At this time there are three design memos:

1. Design.Documentationwhich deals with the design documentation system (This Memo).

2. Design.PPLFlawswhich catalogues the known flaws in the PPL version

3. Design.Extensionswhich catalogues known and straightforward extensions and revisions to the PPL design which have accumulated from its users’ experience.

Two other design memos are under development:

4. Design.DeepIssueswhich catalogues a set of known problem areas in the PPL design which require substantial thought to resolve and/or which would have a major impact on the basic structures of the system.

5. Design.DeclExampleswhich gives some example programs from the PPL code and suggests a set of declarations that might be useful for these programs.

The mechanics of maintaining the specification as it develops out of discussions over the next few months is important. I propose that the design cycle be recorded in a series of memos (of which these five will be the first) which are sequentially numbered, and reside in the IDL directory (or the IDL documentation directory, if we create one) as Bravo format files under names of the form Design.x for a memo on topic x. The complete series of such memos will constitute the design specifications of the project at any given point. This seems to be the least painful way of getting all the decisions down, but it involves a commitment on all our parts to write decisions down as they are made, rather than holding them up to the end.

The development of the design notes in the immediate future is expected to proceed as follows. On the basis of discussions during the next week, a subset of the issues raised in memo 4 will be selected for further discussion, on the basis of perceived importance and tractability, and more detailed design proposals will be drawn up. Each of these should be the subject of at least one design note. Although some problems raised in that memo will not be treated during the first implementation, their discussion should encourage awareness of directions in which the system should be made flexible.

Likewise, as a result of discussions on memo 5, specifications for the declarative facilities to be used in the LISP code will also be drawn up as a design memo. The series will proceed from there in an interrupt driven fashion.