architecture.md

@@ -54,7 +54,23 @@
 
 - Migrate
 
-  Move service configurations and deployment (including user data) from one hosting provider to another.
+  Move service configurations and deployments (including user data) from one hosting provider to another.
+
+- Runtime backend
+
+  A type of digital environment one can run operating systems such as NixOS on, e.g. bare-metal, a hypervisor, or a container runtime.
+
+- Runtime environment
+
+  The thing a deployment runs on, an interface against which the deployment is working. See runtime backend.
+
+- Runtime configuration
+
+  A specification for mapping components of a configuration to the runtime environment, e.g. which services to deploy to which virtual machines, or how to access object storage.
+
+- [NixOps4](https://nixops.dev)
+
+  A tool to interact with mutable external resources based on declarations in the [Nix language](https://nix.dev/manual/nix/latest/language/).
 
 - Resource
 
@@ -67,18 +83,6 @@
 
   > Example: We need a resource provider for obtaining deployment secrets from a database.
 
-- Runtime backend
-
-  A type of digital environment one can run operating systems such as NixOS on, e.g. bare-metal, a hypervisor, or a container runtime.
-
-- Runtime environment
-
-  The thing a deployment runs on, an interface against which the deployment is working. See runtime backend.
-
-- Runtime config
-
-  Configuration logic specific to a runtime backend, e.g. how to deploy, how to access object storage.
-
 ## Technologies used
 
 ### [NixOS](https://nixos.org/)