A Gentle Introduction to CouchDB for Relational Practitioners

"CouchDB is a document-oriented database written in Erlang that addresses a particular "sweet spot" in data storage and retrieval needs. This blog post is an introduction to CouchDB for those of us who have a relational database background."

The short introduction to CouchDB at 

http://blog.couchone.com/post/1167966323/a-gentle-introduction-to-couchdb-for-relational

is a fantastic writing example. Within a few paragraphs the author has conveyed the essence of the tool and for an experience tools user/evaluator the set of next questions that must be answered before it can be put to use -- security, contention, document size boundaries, etc -- can now all be asked discerningly.