The NIEM model was designed to accommodate updates on a regular basis in order to evolve with user needs. To incorporate change on a predictable and sustainable schedule, NIEM has a standard release cycle for model updates.
The NIEM model is decentralized. Individual domains manage their respective content. If a data requirement isn’t already found in the model and is specific to a particular community, a request can be made to the domain’s point of contact for consideration for the domain. The approved updates are then incorporated into the next NIEM release (major or minor) for reconciliation and official publication.
If a data requirement isn’t already found in the overall NIEM model and is applicable to many domains, it can be submitted through the NBAC for consideration for NIEM core. A primary function of the NBAC is to coordinate the ongoing harmonization process between NIEM core and domains.
Harmonization is an ongoing process to reduce duplication in the model as updates are made and it evolves to accommodate new community business requirements. The harmonization process integrates these new requirements while still ensuring data elements exist only once in the model.
The purpose of harmonization is to reduce duplication, but not necessarily to reduce cross-domain dependencies. Domains can and should reuse content from another domain if it is considered to be the authoritative source for the information. Content should only be refactored into Core if there is no clear authoritative source for it and would be better managed by the NBAC.