How can External Components be used within the National Information Exchange Model (NIEM)?
Use of external schemas within NIEM should not require that each must be harmonized with components in or placed directly into NIEM. XML Schema provides namespaces to maintain semantic independence or uniqueness.
There are potentially two ways to use components from an external standard within the
Methods of integrating external components
Profile the standard and insert its components into a NIEM namespace (potentially within Common).
The "standard" components will become part of NIEM.
The "standard" components will be registered with other NIEM components.
The "standard" components will have precise semantics (because they ARE NIEM components).
Anytime the standards change, then NIEM must potentially be changed.
The "standard" components must be factored to conform to the NIEM NDR.
The "standard" components may need to be harmonized with the NIEM components they potentially duplicate in whole or part (from a semantic perspective).
The "standard" components may not be used in the same structural representation as the standard intended.
Interoperability may require translations back to standard structures. (Tools expecting standard geospatial component structures may not recognize or work with those components if they have been re-structured per the NIEM NDR.).
EACH standard that NIEM incorporates in this manner will result in the preceding disadvantages. Thus, insertion will require a lot of unnecessary extra work.
Provide a mechanism to reference and import the standard schemas/namespaces and use the components they contain within IEPDs constructed from NIEM components.
Standards components are used within IEPDs in the same structure they were intended without the need to translate -- a potential boost to interoperability.
Tools designed to recognize (parse) standard components from other namespaces will recognize these components.
No other refactoring, integration, harmonization, or maintenance of these standards is required (even if the standards change).
Components in preferred standards can still be registered with and discovered in a repository of NIEM components (requires storage of metadata about the standards).
Subset schemas of these standards can be maintained and stored locally as required for use within IEPDs, a registry, etc.
A NIEM structure (an adapter or container construct) will be required to encapsulate non-conforming components or schemas within an IEPD schema and to identify and preserve the semantics of those components.