Technical report documenting the methodology adopted in the pdnd-eservices-graph project to build a directed weighted graph of the Italian PDND (Piattaforma Digitale Nazionale Dati) interoperability ecosystem from heterogeneous public sources. Nodes and e-services come from official open datasets. Edges are reconstructed by cross-referencing the structured attributes field of the catalogue with institutional documentation, including circulars, operational manuals and public presentations. Large language models are used as analytical instruments to extract and normalise relational information from unstructured documents, with every inferred connection traceable to a public source. The result is a graph of 51 nodes and 86 e-service types covering approximately 89% of the 14,102 published endpoints in the official PDND catalogue.