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+# datafrog
+
+Datafrog is a lightweight Datalog engine intended to be embedded in other Rust programs.
+
+Datafrog has no runtime, and relies on you to build and repeatedly apply the update rules.
+It tries to help you do this correctly. As an example, here is how you might write a reachability
+query using Datafrog (minus the part where we populate the `nodes` and `edges` initial relations).
+
+```rust
+extern crate datafrog;
+use datafrog::Iteration;
+
+fn main() {
+
+    // Create a new iteration context, ...
+    let mut iteration = Iteration::new();
+
+    // .. some variables, ..
+    let nodes_var = iteration.variable::<(u32,u32)>("nodes");
+    let edges_var = iteration.variable::<(u32,u32)>("edges");
+
+    // .. load them with some initial values, ..
+    nodes_var.insert(nodes.into());
+    edges_var.insert(edges.into());
+
+    // .. and then start iterating rules!
+    while iteration.changed() {
+        // nodes(a,c)  <-  nodes(a,b), edges(b,c)
+        nodes_var.from_join(&nodes_var, &edges_var, |_b, &a, &c| (c,a));
+    }
+
+    // extract the final results.
+    let reachable: Vec<(u32,u32)> = variable.complete();
+}
+```
+
+If you'd like to read more about how it works, check out [this blog post](https://github.com/frankmcsherry/blog/blob/master/posts/2018-05-19.md).
+
+## Authorship
+
+Datafrog was initially developed by [Frank McSherry][fmc] and was
+later transferred to the rust-lang-nursery organization. Thanks Frank!
+
+[fmc]: https://github.com/frankmcsherry