Local and Global Analysis: Complementary Activities for Increasing the   Effectiveness of Requirements Verification and Validation
  This paper presents a unique approach to connecting requirements engineering (RE) activities into a process framework that can be employed to obtain quality requirements with reduced expenditures of effort and cost. We propose a two-phase model that is novel in that it introduces the concept of verification and validation (V&V) early in the requirements life cycle. In the first phase, we perform V&V immediately following the elicitation of requirements for each individually distinct system function. Because the first phase focuses on capturing smaller sets of related requirements iteratively, each corresponding V&V activity is better focused for detecting and correcting errors in each requirement set. In the second phase, a complementary verification activity is initiated; the corresponding focus is on the quality of linkages between requirements sets rather than on the requirements within the sets. Consequently, this approach reduces the effort in verification and enhances the focus on the verification task. Our approach, unlike other models, has a minimal time delay between the elicitation of requirements and the execution of the V&V activities. Because of this short time gap, the stakeholders have a clearer recollection of the requirements, their context and rationale; this enhances the stakeholder feedback. Furthermore, our model includes activities that closely align with the effective RE processes employed in the software industry. Thus, our approach facilitates a better understanding of the flow of requirements, and provides guidance for the implementation of the RE process. 
Lester Lobo, James D. Arthur