Extend README

Signed-off-by: Matthias Beyer <mail@beyermatthias.de>

1 files changed, 37 insertions, 0 deletions

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@@ -9,6 +9,43 @@ Async DAG library generic over Node type, Node Identifier Type and Backend
 Experimental. Do not use.
 
 
+## What is this?
+
+My Problem was, that I wanted to implement a DAG on IPFS/IPLD. The Problem,
+though, is that the existing IPFS/IPLD libraries do not feature functionality to
+build a DAG easily.
+There are libraries for DAGs, but they all implemented the storage functionality
+themselves. I needed a backend that is _async_ and _generic_, so that I can use
+IPFS (or anything else that works async) in the backend. So this lib was born.
+
+This library does define a simple interface for the underlying backend:
+
+```rust
+#[async_trait]
+pub trait DagBackend<Id, N>
+    where N: Node,
+          Id: NodeId + Send
+{
+    async fn get(&self, id: Id) -> Result<Option<N>>;
+    async fn put(&mut self, node: N) -> Result<Id>;
+}
+```
+
+and that's it. The `AsyncDag` type implements the DAG data structure on top of
+that.
+
+
+## Limitations
+
+Because this library was initialized to be used with IPFS in the backend, is has
+some limitations:
+
+* It does assume that you cannot ever delete nodes. You can
+  rewrite the DAG, but this does not necessarily delete nodes.
+
+This list will be extended in the future. Do not assume it is complete!
+
+
 ## License
 
 MPL-2.0