Make attributes in child as nested element decorators

[mozzer]

I have some XML like this:\[code\]<doc> <a a1="1" /> <a a1="1" a2="1" /> <a a2="1" a1="1" /> <a a2="1" /></doc>\[/code\]I need to transform it so that attributes of the node "a" decorate it as nodes, like this:\[code\]<doc> <a1><a /></a1> <a1><a2><a /></a2></a1> <a2><a1><a /></a1></a2> <a2><a/></a2></doc>\[/code\]Would someone be so kind as to point the way to an XSLT solution?