ARE OBJECTS THAT IMPORTANT - EFFECTS OF EXPERTISE AND FAMILIARITY ON CLASSIFICATION OF OBJECT-ORIENTED CODE

This article reports a study of the use of card sorts in the categoriz ation of fragments of abject-oriented (OO) programs. We are interested in the way in which programmers think about code so that we might att empt to provide support for browsing and reuse activities within OO en vironments. As a consequence, we have been exploring the use of knowle dge acquisition techniques in order to elicit programmers' knowledge a bout code. The study reported here required expert and novice programm ers to sort through several cards, each containing a fragment of code. In the case of the expert group, half of the subjects were familiar w ith the code, and half were not. The subjects sorted the cards accordi ng to any criteria they felt were appropriate. Our results showed, con trary to our expectations, that experts tended to focus on the functio nal relations between the code fragments and that the novices were muc h more concerned with objects and inheritance relations. Moreover, tho se experts who were familiar with the code also appeared to focus to a greater degree on functional information compared to those who were u nfamiliar with the code, who derived classifications based on object a nd class relations. We discuss these results in terms of the existing body of knowledge about expertise in procedural programming and with r espect to the claims that have been made about the naturalness of conc eiving the world in terms of objects and their relations. Last, we sug gest several directions for future research into the psychological mec hanisms that might underpin OO design and programming.