The changes to the NIEM technical architecture from NIEM version 2.* to version 3.0 are highlighted below.
Replaced conformant indicator with conformance targets for reference schema, extension schema, conformant schema document set and conformance instance XML document
Added support for local vocabularies
Added structures:ref and merged content and reference elements
Added NDR Schematron rules to normatively define and validate conformance where possible.
Replaced ComplexObjectType with ObjectType and AssociationType
Added multiple representations of code lists (code, literal)
Removed appinfo base
Removed sequenceID, augmentation and metadata elements
Replaced external adaptor type indicator with an attribute
Added external import indicator
Replaced applies-to element with substitution groups for augmentations and applies-to types and applies-to elements for metadata
Replaced link metadata with relationship metadata
Replaced appinfo annotation elements with attributes