The NIEM technical architecture is described in terms of the Core and Domains, and the XML namespaces that are assigned to each. A namespace is a mechanism for uniquely identifying and associating terms with a specific vocabulary, avoiding conflicts in names and definitions.
NIEM consists of two classes of namespaces: Core and Domains. NIEM also uses separate namespaces for code tables. Core namespaces contains data components that are under NIEM Configuration Control, Domain namespaces are organized around functional lines of business and are controlled by representatives from communities of interest participating in the Domain. Core consists of:
Universally shared and understood across all (or almost all) domains. This requires consensus by all domains on the semantics and structure of the component. A harmonization process ensures that NIEM Core components are properly defined, that components are governed by a process that provides effective voice and involvement among all domains, and that NIEM remains a consistent and coherent data model.
Structures which contains components that do not carry information content or have specific semantic meaning but are imported into other namespaces to enable consistent linking and description. The components are also used to connect metadata to objects.
Domains group components by functional lines of business and contain components specific to a respective business line. Domain components may be used by any NIEM participant. Components in NIEM core and the individual domains must conform to the NIEM Naming and Design Rules (NDR), methodologies, and architectural specifications.