Case-based reasoning commentaries: introduction

The special issue of 'The Knowledge Engineering Review' is presented, which marks a significant accomplishment of the case-based reasoning (CBR) community. It has 19 commentaries, which represent a compendium on the state-of- the-art in CBR. CBR is a process in which specific experiences are retrieved, reused, revised, and retained for use in problem solving and interpreting the state of the world. It has been described as a cognitive theory of human problem solving, a paradigm for conducting artificial intelligence research, and as a knowledge engineering methodology for deploying practical systems. The commentaries are organized into five groups that account for the various aspects of CBR.