In this paper, we discuss interactions between XP (eXtreme Programming) practices. We discuss 2 case studies of introducing XP practices selectively from the 13 practices which are defined in XP, and we analyze how to select practices. Our analysis is based on interviews with developers. While it is difficult to introduce all the XP practices at once, our knowledge makes it easier to determine more effective combinations of practices.

Software productline engineering is becoming recognized as an important concept for efficient and timely software development. But to be actually useful, practitioners of software development (designers, programmers, testers, etc.) must have solid understanding and well organized knowledge about productline engineering.So in this workshop, I want to discuss about; What kind of knowledge and skills do we need? How can we gain such knowledge and skills?