E-services are built upon the exchange of information between several databases and institutions. The creation process of new e-services may be not an efficient one because the discovery, integration and reuse of appropriate information resources is time-consuming as the meaning of these information resources is not well-enough documented. In order to describe the meaning of information resources – being poured into hundreds of heterogeneous databases, distributed between several institutions – some coordination, principles, architecture and infrastructure are needed. This paper outlines proposed large-scale semantic interoperability architecture and its pilot implementation in the Estonian public sector's semantic interoperability initiative.