I'm only really familiar with couchdb, and implementing things like tagging are very easy. Couchdb is document based with incremental map/reduce. So for blog

I'm only really familiar with couchdb, and implementing things like tagging are very easy. Couchdb is document based with incremental map/reduce. So for blog tagging, you have a blog document. That has an array of tags or even just the tags on the string. To be able to pull up documents based on tags you can write a view that will execute map/reduce to create a list of tags and the documenets the implement them. So document structure would look like { blogtext: my blog text" tags: ["tag1", "tag2"] } The map function looks like: function (doc) { for each (tag in doc.tags) { emit (tag, doc._id) } } That will generate a list of keys and the document ids that match. So when you execute: http://server/db/desgindoc/_view/tags?key=tag1 http://server/db/desgindoc/_view/tags?key=tag1 you' recieve all of the documents matching that tag. You can of course do more advanced tagging, but this was just a simple example.