Declarative programming: The light at the end of the tunnel

What is declarative programming? We want to be able to tell the computer what to do, easily and reliably. But natively it makes very small changes to a state of a few gigabytes. My best definition: a declarative program doesn’t have very many steps. Some examples: spreadsheets, SQL queries, parser generators, streaming data flow systems, mashups, Mathematica.

Successful declarative systems usually have a few things in common: They are a good match to the user’s view of the problem, they are compositional, they give you big primitives, and they have clean escape hatches.