Table 7. Computable Hierarchies (File = MRHIER.RRF)

CUIUnique identifier of concept
AUIUnique identifier of atom - variable length field, 8 or 9 characters
CXNContext number (e.g., 1, 2, 3)
PAUIUnique identifier of atom's immediate parent within this context
SABAbbreviated source name (SAB) of the source of atom (and therefore of hierarchical context). Maximum field length is 20 alphanumeric characters.  Two source abbreviations are assigned: 
  • Root Source Abbreviation (RSAB) — short form, no version information, for example, AI/RHEUM, 1993, has an RSAB of "AIR"
  • Versioned Source Abbreviation (VSAB) — includes version information, for example, AI/RHEUM, 1993, has an VSAB of "AIR93"
Official source names, RSABs, and VSABs are included on the Source Vocabularies page.
RELARelationship of atom to its immediate parent
PTRPath to the top or root of the hierarchical context from this atom, represented as a list of AUIs, separated by periods (.) The first one in the list is top of the hierarchy; the last one in the list is the immediate parent of the atom, which also appears as the value of PAUI.
HCDSource asserted hierarchical number or code for this atom in this context; this field is only populated when it is different from the code (unique identifier or code for the string in that source).
CVFContent View Flag. Bit field used to flag rows included in Content View. This field is a varchar field to maximize the number of bits available for use.

From: 3, Metathesaurus - Rich Release Format (RRF)

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