> For those that know, would this be akin to Tiles in Struts (in a 
> somewhat different form)?

I looked at both SiteMesh and Tiles before doing layouts in Action 
Pack. So yes, there was indeed inspiration, but mostly in the sense of 
what _not_ to do. I think both approaches are over-engineered to the 
point of being laborious and hard to understand. But I feel that about 
many things, so...

Anyway, in my opinion, the benefit of SiteMesh and Tiles is the 
inversion principle. Instead of having content templates reference 
common layout (through include header/footer and the like), you make 
the layout reference the content. That's where at least 80% of the 
benefit is hidden to me. And layouts in Action Pack implements that for 
5% of the effort (it's really just a string!).
--
David Heinemeier Hansson,
http://www.rubyonrails.org/  -- Web-application framework for Ruby
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http://www.loudthinking.com/ -- Broadcasting Brain
http://www.nextangle.com/    -- Development & Consulting Services