Automation of application provisioning is one of the key aspects of Cloud Computing. Standards such as the Topology and Orchestration Specification for Cloud Applications (TOSCA) provide a means to model application topologies which can be provisioned fully automatically. Many automated provisioning engines require that these topologies are complete in the sense of specifying all application, platform, and infrastructure components. However, modeling complete models is a complex, timeconsuming, and error-prone task that typically requires a lot of technical expertise. In this paper, we present an approach that enables users to model incomplete TOSCA application topologies that are completed automatically to deployable, complete models. This enables users to focus on the business-relevant application components and simplifies the creation process tremendously by minimizing the required effort and know-how. We prove the technical feasibility of the presented approach by a prototypical implementation based on the open source modeling tool Winery. In addition, we evaluate the approach by standards-compliance and performance.