Modern web development increasingly means pushing more logic onto the client. This provides us with fast and responsive interfaces, but not without cost. When grafted onto traditional web-frameworks, rich interfaces require the complete re-implementation of features on both the server and client-side. Form validation, Templating and URL routing must either be handled at both ends or become fragile and insecure.
What's needed is a harmonious environment which shares code between the browser and server, without 'breaking the web'. Search engines and other users should still have access to key content, even if we accept a less featureful experience. This is the problem Kanso was designed to solve, by implementing CouchDB's design doc API in the browser.