Table 2. Recommendation for versioning.

	Recommendation	UniProt	RefSeq	Ensembl
General versioning practices	Primary versioning strategy	Record level	Record level	Release level
	Past versions are accessible	All versions of individual records are accessible http://www.uniprot.org/uniprot/P12345?version=* http://www.ebi.ac.uk/uniprot/unisave/app/#/	All versions of individual records are accessible https://www.ncbi.nlm.nih.gov/nuccore/NM_004333.4?report=girevhist	Maintains all archives for at least 5 years; some key releases may be maintained for longer. All databases maintained for at least 10 years (currently all databases available from 2004) http://www.ensembl.org/info/website/archives/index.html
	Release versioning available	ftp.ebi.ac.uk/pub/databases/uniprot/previous_releases	No past releases available	ftp.ensembl.org/pub and archive sites
	Documentation exists regarding what kinds of record changes prompt a new version to be issued.	http://www.uniprot.org/help/entry_history http://www.uniprot.org/help/uniprotkb http://www.uniprot.org/help/fasta-headers	https://www.ncbi.nlm.nih.gov/books/NBK50679/#RefSeqFAQ.what_causes_the_version_number	http://www.ensembl.org/info/genome/stable_ids/index.html
URL version practices	The base identifier (the one with no explicit version) should resolve (302 redirect) to most recent version.	http://www.uniprot.org/uniprot/P12345	https://www.ncbi.nlm.nih.gov/nuccore/NM_004333	http://ensembl.org/id/ENSMUSG00000033577
	Base identifier should be deterministically convertible from any other version.	Remove dot suffix from the Local ID, e.g.: http://www.uniprot.org/uniprot/P12345.1 to http://www.uniprot.org/uniprot/P12345	Remove dot suffix from the Local ID, e.g.: https://www.ncbi.nlm.nih.gov/nuccore/NM_004333.4 to https://www.ncbi.nlm.nih.gov/nuccore/NM_004333	Remove build number from the URI, e.g.: http://e85.ensembl.org/id/ENSMUSG00000033577 to http://ensembl.org/id/ENSMUSG00000033577
	Older versions must resolve.	http://www.uniprot.org/uniprot/P12345.1	https://www.ncbi.nlm.nih.gov/nuccore/NM_004333.1	http://e85.ensembl.org/id/ENSMUSG00000033577
	Illegal or invalid version should produce an informative http error code and a HTML page explaining the error.	http://www.uniprot.org/uniprot/P12345.302 returns a 400 bad request and brief description	https://www.ncbi.nlm.nih.gov/nuccore/NM_004333.302 returns a 404 page not found	Error not returned
	A list of all previous versions should be available.	See “history” tab in user interface	See format dropdown in user interface	http://www.ensembl.org/info/website/archives/assembly.html
	Link from older version to current version should ideally be provided.	P12345.3	Link available at the top of the page	Plans to support
	Two versions (or dates) should ideally be comparable.	Record history provides comparison	Record history provides comparison	Unsupported

Local ID, local identifier; URI, unique resource identifier; URL, uniform resource locator.