Add Representation Term `Adapter`

[cdmgtri]

Migrated from NIEM/NIEM-NDR#114

Adapter seems like a useful representation term to add and easy to check. It's obvious in the schemas where the hand-off to external content appears, but there's no cue in the instances besides unfamiliar looking content.

We have similar representation terms for associations, augmentations, and metadata. Would like to see adapters treated consistently.

Dr. Scott: It shows up in the element name, just like with Codes.

todo Christina to make XML examples for clarity

[cdmgtri]

We sometimes use Adapter as a representation term for adapter properties and types. For the others, it is sometimes difficult or impossible to tell that they are adapters without looking at what the type contains.

Property	Type
ag:LocationLineStringCoordinates	geo:LineStringType
ag:LocationMultiSurfaceCoordinates	geo:MultiSurfaceType
ag:LocationPointCoordinates	geo:PointType
ag:LocationPolygonCoordinates	geo:PolygonType
cbrn:SpecialEventSecurityArea	geo:PolygonType
edxl-cap:AlertAdapter	edxl-cap:AlertAdapterType
edxl-de:DistributionElementAdapter	edxl-de:DistributionElementAdapterType
edxl-have:HaveAdapter	edxl-have:HaveAdapterType
geo:AreaCurve	geo:CurveType
geo:AreaEnvelope	geo:EnvelopeType
geo:AreaPoint	geo:PointType
geo:AreaPolygon	geo:PolygonType
geo:AreaRegionGeometry	geo:GeometryType
geo:Ellipse	geo:EllipseType
geo:Feature	geo:FeatureType
geo:Geometry	geo:GeometryType
geo:LocationFeature	geo:FeatureType
geo:LocationGeometry	geo:GeometryType
geo:LocationGeospatialPoint	geo:PointType
mo:WaypointPoint	geo:PointType
mo:WGS84LocationEllipse	mo:WGS84EllipseType
mo:WGS84LocationExternalPolygon	mo:WGS84ExternalPolygonType
mo:WGS84LocationLineString	mo:WGS84LineStringType
mo:WGS84LocationPoint	mo:WGS84LocationPointType

Suggestions:

• [ ] Add Adapter as a representation term for adapter types?
• [ ] Add Adapter as a representation term for adapter properties?

Also, a decision for the NBAC, but may want to make adapter namespace prefixes easier to spot and distinguish from external namespace prefixes. We could follow the pattern we use for xs (external) vs niem-xs (proxy):

External	Current adapter	Proposed adapter
xs	niem-xs	niem-xs
cap	edxl-cap	niem-cap
de	edxl-de	niem-de
have	edxl-have	niem-have
gml	geo	niem-gml

[cdmgtri]

Model changes merged into the dev branch for 6.0.