Reactive Server Pages (RSP) bring some concepts of reactive languages to the 
realm of server-side web development.

Traditional server-side web application are implemented as a collection of 
related pages that access the same shared state (i.e. session variables). Once 
the web server receives a page request from the client, it executes the dynamic 
page reading and writing to session variables, and yields a fresh page to the 
client. The request is handled all at once, and no state (besides the client's 
session) remains in the server. Hence, there is no notion of sequential 
execution in a web application, whose life cycle is purely associated with the 
active client session.

RSP rearrange the way web applications are developed. A web application 
conceptually becomes a single file that executes from its first to its last 
line. The programmer can use structured programming with loops and recursive 
calls. RSP are based on LuaGravity, which extends the Lua language with 
reactive data and control primitives.