Joe Gregorio | BitWorking | REST Tip: Deep etags give you more benefits.
http://bitworking.org/news/150/REST-Tip-Deep-etags-give-you-more-benefits
"if a resource is tied to a single row in a table then a simple timestamp or revision number on the row is a good source of information for generating an etag"
ETags: This stuff matters | 2006-12-19 | BitWorking
http://bitworking.org/news/ETags__This_stuff_matters
"This turns a regular GET into a "conditional" GET (wonder twin powers activate)."