[protomyth]

I thought the wikipedia article could explain it better than I, but here are some more references:

http://blogs.kde.org/2006/10/21/ralph-griswold-icon-language...

http://dl.acm.org/citation.cfm?id=104659

http://research.microsoft.com/pubs/69724/tr-99-64.ps

look at Goal-directed evaluation of icon