Articulating semantic interoperability in e-Government remains in question as long as the international standardization efforts do not reach a consensus on how to semantically annotate and exchange data, but merely focus on the syntactic aspects by publishing sets of XML Schemas. As one-stop governmental services at national and cross-county level become an imperative, the need for standardized data definitions, codification of existing unstructured information and a framework for managing governmental data in a unified way emerges. Effectively applied to the Greek e-Government National Interoperability Framework, this paper proposes a methodology for designing semantically enriched XML Schemas with which homogenized governmental information complies, based on the UN/CEFACT Core Components Technical Specification (CCTS). A discussion around a prospective architecture for managing large sets of XML Schemas is also motivated in order to recognize the necessary components and the key issues that need to be tackled when designing a Governmental Schema Registry.