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All identifiers in GO (e.g. referenced in GAF, ontology or associated documents) should be conform to the following format:

 GlobalID = Prefix ':' LocalID

We use the term 'identifier' as synonymous with GlobalID, although confusingly some use 'identifier' to refer to what we call LocalID.

  • Prefixes (aka Database): Each prefix must be registered in the GO xrfs registry file. It should correspond to some known authority. The characters must all be alphanumeric (a-z, A-Z, 0-9), underscores or dashes.
  • The LocalID scheme is under the control of the Database/authority. The characters must all be printable ascii characters, excluding spaces.


Examples of well behaved IDs:

  • GO:0008152
    • Database=GO LocalID=0008152
  • SGD:S000006435
    • Database=SGD LocalID=S000006435
  • ZFIN:ZDB-GENE-980526-166
    • Database=ZFIN LocalID=ZDB-GENE-980526-166

Identifiers in GAFs


In the gene association (GAF) files, the global ID is split across two column: Database goes in column 1, LocalID goes in column 2

For filling in the WITH column, the Global ID should be used. This has to be the case, otherwise it would be difficult to tell where the ID came from

Prefix Registry

The Database should be registered in GO.xrf_abbs, available here:


We are in the process of moving the primary version of this file to a yaml file with primary location in a github repo:

Identifiers, CURIES and URIs

The GO uses semantic web standards such as OWL and RDF. In these standards, URIs are used to uniquely identify ontology terms, genes and associated provenance entities such as publications.

In order to reconcile URIs with the identifier scheme used in formats such as obo, GAF, and how we display identifiers in publications and portals such as AmiGO, we conceive of GlobalIDs as *Compact URIs* (CURIES).

We assume a constant set of prefixes. For all ontologies used in GO, we assume that these have an OBO library PURL URI, so we have an implicit set of prefix declarations:

  @prefix GO:
  @prefix CL:
  @prefix CHEBI:

Problems with existing usage


We have both FB and FlyBase registered here Also in the fb gene_association files, the col1 is FB but the assigned_by column is FlyBase. NCBI seem to use FLYBASE

Josh has been alerted, bringing this up with FlyBase

MGI and prefix doubling

MGI IDs are a major problem

GAF (cols 1-3):

 MGI     MGI:98297       Shh

Using the concatenation rule, this composes to the global ID

  • MGI:MGI:98297

Here we have a doubling up of the MGI prefix.

Note that NCBI previously used 'non-doubled- global identifiers of the form MGI:nnn, but they are now switching to the doubled form MGI:MGI:nnn - see article from Wed, 06 Aug 2014 "Important change coming for HGNC and MGI database identifiers"

Compare with the (well-behaved) ZFIN GAFs and IDs:

 ZFIN    ZDB-GENE-980526-166     shha

(example col1,2,3 in GAF)

col1:col2 =

  • ZFIN:ZDB-GENE-980526-166

This is identical to what NCBI uses in their xref

MGI previously confirmed that the global ID is MGI:MGI:nnnnn, and the local internal ID is MGI:nnnn (but this seems to have changed)


RGD previously used the same pattern as MGI. As of 2008/06/23 they have confirmed their policy and fixed their files. RGD:nnnn is the global ID. The local ID is purely a number (for both genes and references)


MGI should either

  • change their col2 in their GAFs such that only the number is used (PREFERRED)
  • coordinate with other databases, including NCBI to make it clear that the global ID is MGI:MGI:nnnnn

See Also