Platform-as-a-service offerings continuously gain importance as two-sided markets, offering Software-as-aService (SaaS) to the respective customers. Market success is achieved by platforms, which excel in shaping ecosystems of users and autonomous SaaS suppliers around their basic value proposition -and in controlling quality of service in function of customer requirements. In this paper, we suggest a notation for dynamic networks 'DYNO', designed to help platform providers in creating PaaS, optimized on their specific requirements. In addition, DYNO gives support in properly allocating control mechanisms to guarantee high quality of service. In a use-case we describe how business analysts and service engineers may use DYNO-models to conceive PaaS ecosystems..