A database authority. Typical databases in bioinformatics are FlyBase, GO, UniProt, NCBI, MGI, etc. The authority is generally known by this shortened form, which is unique within the bioinformatics and biomedical realm. To Do - add support for URIs, URNs (e.g. LSIDs). We can do this by treating the URL as a URI - however, some applications may expect this to be resolvable - to be decided.
A unique, global, public, stable identifier. Not necessarily an external reference - can reference data items inside the particular chado instance being used. Typically a row in a table can be uniquely identified with a primary identifier (called dbxref_id); a table may also have secondary identifiers (in a linking table _dbxref). A dbxref is generally written as : or as ::.