ndows Mobile. In case one or more of the interfaces are successful in meeting the essential requirements of the majority of the application domains they will enter the Adoption phase. Most of the applica- tions start to use these interfaces as a platform due to their large potential customer Model for Evolution of a Vertical Software Industry base. After a race for market share, one of the interfaces is likely to reach the position of a dominant design ("Software interface 1" on the right) in the Service and Variation phase. There may still exist some niche markets for competing interfaces ("IF 2") such as Apple competing with Microsoft in the operating system interfaces. New software vendors (ZZ, M, and YY in Fig. 2) will then consider it useless to compete with this dominant design and start, instead, building additional software layers on top of it. For example, after the SQL interface became the dominant design for accessing databases, further layers , such as ODBC, JDBC etc., were build on top of it. Figure 2 represents the reasons for vertical dis-integration that is realized in increasing number of software layers provided by independent software vendors. This development will also reduce the effort needed for developing the software needed to support a specific process or to interface a specific hardware, as there exists an increasing volume of software that can be used as a base-line for any new software. However, new software requires typically multiple interfaces to interface with multiple hardware-based functionalities. As an example, a software organization needed for implementing a basic retail banking system is considered in Table 2. This system needs to interface with the customers, be able to deliver notes and communicate with a teller, and have a mainframe computer with a database man- agement system connected to the server (on the left). For a long time, the interfaces available to these technologies were proprietary, thereby limiting the number of vendors to a few (see configuration A in the m