ORIGINAL ARTICLE An economic approach for improving requirements negotiation models with inspection Received: 22 May 2002 / Accepted: 15 September 2002 / Published online: 13 May 2003 Ó Springer-Verlag London Limited 2003 Abstract Stakeholder goals identified during require- ments elicitation are usually informal and incomplete statements about a system considered for development. There are numerous approaches for capturing such informal models. For example, we have found the EasyWinWin requirements negotiation method to be an efficient way for attaining consensus among the success- critical stakeholders. The WinWin negotiation model captures stakeholder goals as win conditions, issues, options and agreements. When such a model has to be transformed into more formal representations, quality becomes particularly important. Approaches for vali- dating such informal models can increase quality and provide guidance for further refinement of requirements. Inspection is a proven approach to identify defects and is also applicable to early life cycle artifacts. This paper reports on an empirical study demonstrating the use- fulness of an inspection technique for requirements negotiation models. The study employs a conservative economic model, which considers the effect of defect slippage during development on defect detection benefits from inspection. The main finding of the study is that inspection is an economic validation technique for requirements negotiation models. There are, however, certain limitations that need to be studied in more detail. Keywords Inspection techniques Æ Requirements negotiation Æ Stakeholder-based reasoning Æ Validation of best-practice models 1 Introduction Involving success-critical stakeholders is recognized as an important principle to increase the likelihood of project success. For example, the WinWin spiral model of software development [1, 2, 3] requires the involve- ment of stakeholders in each spiral cycle to identify and reconcile stakeholder objectives. The WinWin negotia- tion approach uses win conditions, issues, options and agreements [4] to build the negotiation model. However, the outcomes of such interactions among stakeholders are typically informal models of the system to be devel- oped. Especially in project inception these models lack precision and contain defects. Evolving and refining such incomplete models into more formal representations or deriving plans from such models can be risky and chal- lenging. As negotiation models provide the rationale for requirements definition and represent an important input to actual development they should be as clear, correct, consistent and complete as possible with respect to a defined negotiation purpose and project phase to avoid serious negative consequences on contract development, project planning or system architecting [5]. There is a general consensus that low-quality requirements typically have negative impacts on the entire software life cycle: For example, Rule [6] reports on several industrial projects badly affected by poorly understood, ambiguous requirements. Kamsties et al. [7] describe problems related to ambiguities in natural lan- guage requirements. The need to focus on quality in requirements engineering (RE) has been pointed out by several authors: El Emam et al. [8] describe a detailed method to measure the success of RE approaches em- phasising three major factors: (a) the cost effectiveness of the RE process; (b) quality of RE products; and (c) the quality of service provided by RE staff. Lauesen and Vinter [9] assess the capability of RE techniques to prevent defects in requirements. Macaulay [10] presents a thorough list of requirements for RE techniques including quality assurance aspects. Requirements Eng (2003) 8: 236–247 DOI 10.1007/s00766-002-0155-8 Michael Halling Æ Stefan Biffl Æ Paul Gru¨nbacher M. Halling (&) Æ P. Gru¨nbacher Systems Engineering and Automation, Johannes Kepler University Linz, Altenbergerstr. 69, 4040 Linz, Austria E-mail: mh@sea.uni-linz.ac.at S. Biffl Institute for Software Technology, Vienna University of Technology, Karlsplatz 13, 1040 Vienna, Austria