Study on Licensing and Program Understanding for Reuse Support

For developing reliable software, it is important to reuse existing software components. Reusable components are not only their developer’s own, but also Open Source Software. In addition, there are hosting services to support developing and sharing open source software recently. As a result, it has been easier to search or distribute reusable components. When reusing or distributing reusable components, there are a lot of concerns. In particular, software license, retrieval for reusable components implementing a feature, extraction of a reusable component are major important issues addressed in this dissertation. Software license permits or forbids the usage of the software including reuse. If a developer violates a license statement of a reused component, the developer may have to stop developing or receive some legal actions. Therefore, the selection of the software license seems to affect to reuse activity, but not surveyed quantitatively. For encouraging active reuse activities, the impact of a software license should be known to the developers. A developer needs to retrieve a reusable target using search engines, because the number of existing open source software is very large. Since major search engines often uses keyword-based search, a reuse target should include a keyword representing its feature. The targets of keyword-based search includes the source code of the software which contains names of identifiers. Identifier names are also important for understandability of the source code since a developer generally tries to guess a role of a program element from identifier names. However, unfortunately, not all developers are able to give appropriate names to identifiers, since a broader knowledge and a great deal of experience are necessary to define accurate names. After a reusable target is found, reuse will complete if a feature of the target is incorporated into a user’s product. However, it is not easy since a developer often has to extract a component implementing the reuse target feature from the found reusable target. For supporting the extraction, program slicing based techniques are proposed previously. In addition, there