The purpose of this site is to introduce the System Dynamics model developed for the paper, "The Transition Problem in Product Development". The model is composed of five sectors, Advanced Work, Current Work, Current Defects, Market Defects and Capacity Allocation. Each sector is discussed in detail in separate web pages.

The reader may download the actual model and simulate it using the Vensim Model Reader software. The Vensim Model Reader can be downloaded using the link provided in the Download page. There is also a Simulation page dedicated to show which variables in the model one must change to generate the results in the paper.

The Download page also has the PDF version of the paper and the technical documentation for the System Dynamics model.

The model represents a product development system that introduces a new product into the market at a fixed time interval called the model year. Two model years are required to develop a product, so at any moment in time two development projects are under way. New projects are introduced into the system at fixed intervals coinciding with the product introduction date. The development cycle is divided into two phases of equal length. The first is the up-front or advanced phase while the second is the current phase. These phases are represented in the Advanced Work Sector and the Current Work Sector, respectively.

Within each phase there is a set of tasks to be completed. Although developing a real product requires a variety of different activities, in the model these are aggregated into two types of tasks, advanced and current. Current tasks represent those activities required to physically create the product, mainly detailed design and engineering. Advanced tasks are those activities which make the subsequent current work more effective, including documenting customer requirements and establishing the feasibility of the technologies planned for the product. Only one type of resource, engineering hours, is needed to accomplish both types of tasks. This is further documented in the Capacity Allocation Sector.

When a project reaches the current phase, there is some probability, P_D, that each task is done incorrectly, must be reworked, and, thus, requires additional resources. Critically, P_D is a function of the number of advanced tasks completed when the project was in its advanced phase. This structure, explained further in the Current Defects Sector, creates dependence between projects since the decision to allocate resources to a project in the current phase affects not only that project, but also the project in the advanced phase.

The measure of system performance used in this study is the quality of the product at its launch date measured as the fraction of its constituent tasks that are defective. The Market Defects Sector explains this "Fraction Defective at Launch" in detail.