Requirements engineering is a field of knowledge concerned with the systematic process of eliciting, analyzing and modeling requirements. Requirements engineering is usually understood in relation to software system requirements, most of its principles and some of its techniques can be adapted to other problems dealing with complex sets of requirements. The engineering vision indicates that this should be a practical and well-defined process where trade-offs have to be considered to obtain the best results. Mature software development needs mature requirements engineering. This was true ten...