Change, similarity and redundancy in software systems

研究表明，高达80%的软件开发成本花在软件维护上。软件维护的一个方面是处理重复代码。复制和粘贴代码段，无论是否进行微小更改，都是一种常见的软件开发实践，随着时间的推移，大型软件系统会开发出许多这样的“软件克隆”。虽然这种克隆通常是故意的，并且在许多方面都很有用，但它可能会在大型软件系统的维护中造成重大问题，因为它增加了更新异常的风险，增加了程序大小和复杂性，并导致了高昂的维护成本。因此，克隆检测是软件维护研究中的一个重要问题，也是广泛的软件工程任务的基础。在过去的几年中，我们在检测和分析险些遗漏的软件克隆方面取得了显著的进步，这些克隆在复制的片段中进行了微小的添加、删除和修改。

Studies show that up to 80% of software development cost is spent on software maintenance. One aspect of software maintenance is dealing with duplicated code. Copy-and-paste of code sections with or without minor changes is a common software development practice, and over time large software systems develop many such "software clones". While such cloning is often intentional and can be useful in many ways, it can cause significant problems in the maintenance of large software systems because it increases the risk of update anomalies, increases program size and complexity, and contributes to high maintenance costs. Clone detection is thus an important problem in software maintenance research, and serves as the basis of a wide range of software engineering tasks. In the last several years, we have significantly advanced the state-of-the-art in the detection and analysis of near-miss software clones, those where minor additions, deletions and modifications have been made in the copied fragments.