Computing Structural Types of Clone Syntactic Blocks

A clone classification scheme is presented based on the structure of the abstract syntax tree (AST) of a system and on the similarity measures between syntactic blocks of source code. Syntactic blocks in a system may represent classes, methods, statement blocks, and so on. An inclusion relation may exist between the source code lines of some of these blocks, depending of the syntactic structure of the source code. For example, a block corresponding to a method body may contain several possibly nested statement blocks.This paper introduces an algorithm to identify different types of clone relations between blocks that are either method bodies or statement blocks. Clone relation types between these blocks are interesting because they indicate properties of the structural relation of these clones and may give hints on re-factoring opportunities. The proposed structural type clone classification scheme has been investigated on two open source Java systems, Tomcat and Eclipse. Experimental results are presented. Execution time performance of clone classification has been measured and reported. Results and further proposed research are discussed.