In the context of ongoing digitalization, manufacturing companies face new challenges and the need to expand their portfolios to include new digital services. Enriching their portfolio with digital services can be an opportunity for manufacturing companies to position themselves in emerging collaborative production networks and thus make their business model fit for the future. The paper ties in with the activities from the Product Lifecycle Enrichment as a Service (PLCEaaS) research project. Within this context, use cases for digital services have already been derived, modelled, and documented in various workshops. The respective digital services directly address external customers and internal stakeholders from development. The central enabler for the new digital services is the digital twin based on the asset administration shell, which makes the necessary data available and thus supports interoperability. The asset administration shell is enriched with use case-specific submodels. The procedure for structuring these submodels is shown in this paper using the research project as an example. This includes modelling the digital services with a standardized modelling language based on the semi-structured use cases described so far. As a result, we obtain an asset administration shell enriched with several submodels - some of which may be based on standardization activities already underway or represent proprietary submodels. Likewise, it is considered whether more submodels are required to implement the domain-specific use cases that are currently not yet addressed in standardization activities. The paper ends with an outlook on the further research activities that are necessary to prototype the planned project and describes which criteria can be used to evaluate the defined submodels in the later course of the project.