pment. The data used includes the OSS/BSS vendor revenues from the years 2000, 2002, 2005, and 2006, and it covers 187 companies of the approxi- mated total of 250 companies present in the OSS/BSS industry. Therefore, the data excludes the smallest and only regionally operating vendors. This is the only market research data available to the authors which provides vendor specific information for the OSS/BSS. The data is based on the vendors' self evaluation. In addition to the data by Dittberner Associates, commercial data sets by other market research firms (ThomsonOne, Amadeus, ArcChart, Forrester, etc.) were used. Whenever possible, public sources of information, such as TMF, ITU, CDMA2000, GSMA, LightReading, and OSS Observer, were used as well. When necessary, additional information was obtained through the Annual Reports of the OSS/BSS companies and CSPs. Finally, in order to obtain a deeper insight into the developments in the OSS/BSS domain, available commercial and public datasets were augmented with the quali- tative data gathered in the course of interviews with representatives of CSPs and telecom service providers in Europe and in the Far East. Besides, valuable informa- tion was obtained by consulting visiting domain experts. 4 Outline of the Book The remainder of the book is organized into four parts as follows: Part I. Evolving Software Markets The first chapter starts by describing the birth of the software industry as a spin- off of computer manufacturing industry and outlines the role of vertical software industries in the intersections of the primary software industry and other industries purchasing specialized software systems for the needs of their core business processes. The three perspectives of analysis are introduced: vertical industry business processes, technologies used through software interfaces and software market. Introduction The second chapter reviews theories related to vertical software industry evolu- tion. These include innovation diffusion theory, evolution of the product du