Requirements gathering and conceptual modeling are essential for the customization of digital libraries (DLs), to help attend the needs of target com-munities. In this paper, we show how to apply the 5S (Streams, Structures, Spaces, Scenarios, and Societies) formal framework to support both tasks. The intuitive nature of the framework allows for easy and systematic requirements analysis, while its formal nature ensures the precision and correctness required for semi-automatic DL generation. More specifically, we show how 5S can help us define a domain-specific DL metamodel in the field of archaeology. Finally, an archaeological DL case study (from the ETANA project) yields informal and formal descriptions of two DL models (instances of the metamodel).