What is semantic interoperability and why is it harder than technical interoperability?

Semantic interoperability means that when data is exchanged between systems, the receiving system understands the meaning identically to the sending system. It requires shared terminologies (SNOMED CT, LOINC), agreed data models (FHIR profiles), and consistent value sets. It is harder than technical interoperability (simply transporting data) because clinical concepts are complex, context-dependent, and evolve over time — the same word can mean different things in different clinical settings.