VIAF is a project to make libraries across the world talk "the same language", much in the same way MusicBrainz is aiming to make music sites, services, programs "talk the same language" (MBIDs). Read more about it on Wikipedia: https://en.wikipedia.org/wiki/VIAF

I propose to add a new URL relationship type as a subtype of the "Other databases" URL relationship type. I discussed it briefly with reosarevok on IRC: http://chatlogs.musicbrainz.org/musicbrainz/2013/2013-01/2013-01-17.html#T12-53-30-734916

The relationship would go on Artists, Labels, and Works. See the WikiProposalPage: https://wiki.musicbrainz.org/User:Freso/VIAF_Relationship_Type

A few examples:
http://viaf.org/viaf/109231256
http://viaf.org/viaf/16766997
http://viaf.org/viaf/152662182