The COTS-based development model in  illustrates the differences between COTS-based development and traditional software development, such as new, re- duced, or modified activities. The underlying assumption of this model is that the rate or degree of using OTS components is fixed in the very early phases of a project and that the main development process has to be modified accordingly. The model can therefore be used as a reference in scenarios 1 to 3.
Fig. 4. Scenario 1 to 3
5.2. Scenarios of unplanned OTS-based software development
In these scenarios (see Figure 5), the decision of using OTS component was not planned or made in advance, i.e. there is no clear intention of using OTS components in the early phases of such a project. Project members decide on the main develop- ment process according to some non-OTS relevant factors, such as company rules and requirement stability. Due to the time-to-market pressure or internal capability, pro- ject members start to evaluate the possibility of using OTS components at certain stages of the project. At an industrial seminar , several industrial participants mentioned such conditions. According to the project members’ familiarity with the OTS candidates, we classify three scenarios from scenario 4 to 6.
Scenario 4 – Unplanned OTS-based project with unfamiliar OTS candidates: In this scenario, the project members decided to use OTS components in a late phase of the project, such as detailed design or coding. However, they do not have any previous experience with the possible OTS candidates. Therefore, the use of OTS components may bring several problems for the whole project. They need a second risk-evaluation to investigate whether the development process should be modified concerning the use of OTS components. For ex- ample, in projects with pure waterfall processes, the project members may need to add a short prototyping step to evaluate the OTS component and to negotiate the use of OTS component with their customer.