Many software acquisition projects are doomed to fail due to a lack of integration of acquisition and development processes on the one hand and, because of shortcomings of classic software development processes on the other hand. In our studies we focus on public sector where legal restrictions make software acquisition more challenging than in private sector. As a consequence we developed an approach for interlocking development processes and acquisition processes using the negotiated procedure (see [18]). Current award platforms only support publication of documents produced in acquisition process. In contrast to the state of the art we are developing a web based public tender support system called PTSS that uses our approach guiding all stakeholders playing different roles supporting iterative procedures proposed by software development processes like eXtreme Programming or the Rational Unified Process. This role based approach has basic impact on data models and other design targe...