The standardization of network configuration interfaces for use with the NETCONF protocol requires a structured data modeling environment which promotes human usability, multi-vendor interoperability, and reuse of existing IETF data models written in SMIv2. The Network Configuration Extensions (NCX) are a set of specifications intended to address NETCONF data modeling issues. This document defines a Structure of Management Information (SMI) suitable for use with the NETCONF protocol, intended to promote a more consistent, manageable, and interoperable infra-structure for ongoing development of NETCONF- based management interfaces.