This book contains the refereed proceedings of the 4th International Conference on Lean Enterprise Software and Systems, LESS 2013, held in Galway, Ireland, in December 2013.

LESS fosters interactions between practitioners and researchers by joining the lean product development and the agile software development communities in a highly collaborative environment. Each year, the program combines novelties and recent research results that make new ideas thrive during and after the conference. This year, the conference agenda was expanded to incorporate topics such as portfolio management, open innovation and enterprise transformation.The 14 papers selected for this book represent a diverse range of experiences, studies and theoretical achievements. They are organized in four sections on lean software development, quality and performance, case studies and emerging developments.

This book describes a parametric model that can help people reason about their decisions related to systems engineering. COSYSMO, the Constructive Systems Engineering Cost Model, contains eighteen parameters: four size drivers and fourteen effort multipliers. It is built on a framework similar to its well-known predecessor, COCOMO II, and integrates accepted systems engineering standards to define its scope. The model focuses on large-scale systems for military applications that employ a disciplined approach to systems engineering. Data were collected from six aerospace companies in the form of expert opinion and historical project data to define and calibrate the model. In reduced form, the model yields a PRED(30) of 50% for programs within a defined productivity range. The audience for this book is twofold: (a) those interested in the theoretical and methodological domain of systems modeling in the quest of a more quantitative cost estimation framework, and (b) those interested in advancing the state of practice in the assessment and tracking of systems engineering in the development of large aerospace systems.