This type of database already exists for Scottish dances: <http://my.strathspey.org/dd/>. It has written and diagram descriptions, links to videos, ratings and comments and a database searchable by figure, author, music type &c. I use it most weeks to pick appropriate music from my club's collection, when we don't have a recording intended for the dance in question. It helps that quite a lot of the legwork has already been done e.g. MiniCrib, an existing unofficial publication of abbreviated dance instructions in a standard form, and there being a standard set of diagrams for figures. Not that this wouldn't be possible for contra, but it would be more work to start from scratch / different styles of crib. If I understand correctly, only the (volunteer) administrators can add dances, but members of the public can comment on and rate dances if they have logged in, and submit cribs or video links, which are approved by moderators. Evolution of dances by the folk process has certainly been documented (which shoulder to pass in Mairi's Wedding, popular variations in the possibly-palindromic Ian Powrie's Farewell to Auchterarder), but I get the impression such variations are less common in SCD (published programmes of existing dances people might practise in advance, rather than the caller calling their favourite version on the night). Edmund Croft, Cambridge, UK