due to high development costs. Chapter "Market Polarization due to Difference in Interface Implementation Efforts" analyzes the impact of continuously emerging new interfaces to network technologies due to new standards and new product generations. One of the predicted consequences is splitting of the OSS/BSS market into a submarket of large incumbent operators served by large software vendors providing knowledge for a large set of network interfaces and a submarket of commencing operators served by commencing software vendors adopting only standard network technol- logies supported by inexpensive software products. The last chapter entitled "Barriers to Horizontal Development" analyzes the impact of patents, licenses, and their distribution to the market evolution. Part IV. Future Scenarios for the Telecom Operator Software Market and Their Evaluation Part IV outlines future scenarios for the OSS/BSS software market. The first chapter uses the Delphi method to evaluate and prioritize 16 most interesting miniscenarios of market evolution derived from the previous parts. The second chapter presents a Manager's Toolbox for analysis of the OSS/BSS market. It represents a base-line scenario containing the past and present major events impacting the OSS/BSS market. The most relevant miniscenarios of the first chapter are attached to the base-line scenario as alternative elements of the base-line scenario. For each miniscenario, the toolbox presents the logic behind the miniscenario and threshold metrics for following the possible realization of the miniscenario. The last chapter provides guidelines for developing further miniscenarios for the OSS/BSS market. This method can also be used for analyzing another vertical software industry (such as retail banking software market or automotive industry software market) and for creating a manager's toolbox for it. Introduction Related Publications This book, containing contributions from numerous researchers, summarizes the main results of the SmarTop project. Parts of the w