“…As yet, there is no consensus on how to describe and measure system NFR. In current practice, they may be viewed, defined, interpreted and evaluated differently by different people in the later project phases, particularly when they are stated vaguely and only briefly in the system requirements phase (Abran et al, 2013;Al-Sarayreh et al, 2012a, 2012bMeridji et al, 2013). It is challenging, therefore, to take them into account in software estimation and software productivity benchmarking, particularly as they have received less attention in the software engineering literature and are definitely less well understood than other cost factors (Chung and Leite, 2009).…”