As the construction industry advances towards digitalization, the efficient and secure exchange of digital data between project partners becomes increasingly critical. Two essential characteristics of a future-proof digital data exchange are the use of well-structured data and controlled access management. Dataspaces address these requirements by providing a digital environment that enables secure, standardized, and convenient data sharing. Developing a dataspace for a specified industry requires not only establishing technical infrastructure but to understand industry-specific processes and their corresponding data exchanges. By analyzing typical processes, different use cases can be identified and formulized. This paper proposes a systematic approach to describe and structure these use cases to facilitate their implementation within a dataspace. The approach begins with decomposing the use cases into manageable process-chains with a particular focus on data exchange among stakeholders. A predefined variable system is introduced to characterize each transaction and address the central question of who needs which data from whom and when. Assets, personas and their relevant properties are systematically identified to structure the data involved. Existing ontologies are applied to formally represent their connections and relationships. Together with the detailed information about the process and its transactions the use cases can then be implemented within the dataspace. The work described above is part of the research project Construct-X.