2 - CONSTRUCTING ABSTRACTIONS FOR OBJECT-ORIENTED APPLICATIONS

Summary

There are two notable points to make about this paper. First, it is one of the first times Ward and I published any pattern-related material (we presented some stuff at OOPSLA 87 in Orlando, I in Norm Kerth's “Where Do Objects Come From” workshop, Ward on a panel). Second, it argues that the worst problem of reuse is one of communication, not technology or economics.

The paper started out life as a Tektronix technical report. Ward and I had the habit of writing up just about everything we did as a TR. After we had written this, I think we submitted it as a position paper for some conference or workshop. Somehow, JOOP got hold of a copy and contacted us about publishing it.

The paper can be summed up as: “We created two sets of abstractions. The first was communicated as literate source code. The second was communicated as patterns for its reuse. The first set of objects was misused; the second was used correctly. We conclude that the problem of reuse is one of effectively communicating the intent of the code.”

MAKING ABSTRACTIONS

We have found Smalltalk's notion of objects communicating with messages an effective vehicle for the express of algorithms and data structures in a form isolated from the details of an application program. The process of isolation, called abstraction, is emerging as a principal activity of programmers.