The org.apache.sis.internal.jaxb.gco package conceptually defines two complementary objects:
ObjectIdentification and ObjectReference. However, only the latter is defined by
a Java class, because the former is implicitly defined by the classes in the public API of SIS.
This page contains the information that we would have put in ObjectIdentification Javadoc
is such class existed.
The gco:ObjectIdentification XML attribute group is implicitly included
by all metadata types defined in the org.apache.sis.metadata.iso packages.
The attributes of interest defined in this group are id and uuid.
This gco:ObjectIdentification group is complementary to gco:ObjectReference,
which defines the xlink and uuidref attributes to be supported by all metadata
wrappers in the private org.apache.sis.internal.jaxb.metadata package and sub-packages.
gml:id and gco:uuidThe GML identifiers page said:
id is a standard GML attribute available on every object-with-identity.
It has type="xs:ID" - i.e. it is a fragment identifier, unique within document scope only,
for internal cross-references. It is not useful by itself as a persistent unique identifier.uuid is an optional attribute available on every object-with-identity, provided in
the GCO schemas that implement ISO 19115 in XML. May be used as a persistent
unique identifier, but only available within GCO context.However, according the OGC/ISO schema, those identifiers seem to be defined in the GCO schema.