  Developing web applications requires dealing with their distributed nature
and the natural asynchronicity of user input and network communication. For
facilitating this, different researchers have explored the combination of a
multi-tier programming language and functional reactive programming. However,
existing proposals take this approach only part of the way (some parts of the
application remain imperative) or remain naive, with no regard for avoiding
glitches across network communication, network traffic overhead, compatibility
with common APIs like XMLHttpRequest etc. In this paper, we present Gavial: the
first mature design and implementation of multi-tier FRP that allows
constructing an entire web application as a functionally reactive program. By
applying a number of new ideas, we demonstrate that multi-tier FRP can in fact
deal realistically with important practical aspects of building web
applications. At the same time, we retain the declarative nature of FRP, where
behaviors and events have an intuitive, compositional semantics and a clear
dependency structure.
