The Unison Programming Platform

Unison - a next-generation programming platform, by Paul Chiusano:

• Programs are edited in a (browser-based) semantic editor which guarantees programs are well-formed and typecheck by construction
• The codebase is a purely functional data structure
• The program is a UI, and UI interaction is programming
• Persistent data sources must be accessible via a high-level, typed API

An interesting project mentioned in a comment a few weeks ago, it now has its own website and a more descriptive abstract overview explaining it's core premises.

Previous posts on Paul's blog are also of interest, and some feature videos demonstrating some aspects of Unison.