diff --git a/deployment/data-model-test.nix b/deployment/data-model-test.nix
index dcaf8a41..4db7d9af 100644
--- a/deployment/data-model-test.nix
+++ b/deployment/data-model-test.nix
@@ -37,13 +37,20 @@ in
             applications.foo.module =
               { pkgs, ... }:
               {
-                environment.systemPackages = [
+                options.doll = lib.mkOption {
+                  type = lib.types.str;
+                };
+                config.environment.systemPackages = [
                   pkgs.hello
                 ];
               };
             deployments.baz = {
-              module = { };
               inherit runtime-environment;
+              application-configuration = {
+                foo = {
+                  doll = 123;
+                };
+              };
             };
             migrations.boo = {
               inherit runtime-environment;
@@ -56,7 +63,7 @@ in
         has-provider = lib.isAttrs example.providers.ssh-host;
         has-resource = lib.isAttrs example.resources.bar.runtime-environment.ssh-host.module;
         has-application = lib.isAttrs example.applications.foo.module;
-        has-deployment = lib.isAttrs example.deployments.baz.module;
+        has-deployment = lib.isAttrs example.deployments.baz.application-configuration.foo.doll;
         has-migration = lib.isAttrs example.migrations.boo.deployment;
       };
     expected = {
diff --git a/deployment/data-model.nix b/deployment/data-model.nix
index 502071e1..71dba8ad 100644
--- a/deployment/data-model.nix
+++ b/deployment/data-model.nix
@@ -120,12 +120,47 @@ let
     modules = [
       {
         options = {
-          # the `applications` option consists of configuration for the above applications
-          module = mkOption {
+          application-configuration = mkOption {
             description = ''
               Configuration to be deployed
             '';
-            type = deferredModule;
+            # # error: attribute 'foo' missing
+            # type = deferredModule;
+            # type = submodule {
+            #   # # checks types but is hard-coded
+            #   # options = {
+            #   #   foo = mkOption {
+            #   #     # type = str;
+            #   #     type = submodule {
+            #   #       options = {
+            #   #         doll = mkOption {
+            #   #           type = str;
+            #   #         };
+            #   #       };
+            #   #     };
+            #   #   };
+            #   # };
+            #   # # `error: attribute 'doll' missing` in `example.deployments.baz.application-configuration.doll`
+            #   # freeformType = attrsOf deferredModule;
+            #   # options = mapAttrs
+            #   #   (k: application: mkOption {
+            #   #     description = "configuration options for ${k}";
+            #   #     # # error: attribute 'doll' missing
+            #   #     # type = deferredModule;
+            #   #     # # XXX doesn't work as `import` is for paths
+            #   #     # type = submodule { inherit (import application.module { }) options; };
+            #   #     # # XXX doesn't work as `evalModules` is general, not recognizing nixos stuff like argument `pkgs` or `config.environment`
+            #   #     # type = submodule {
+            #   #     #   inherit (lib.evalModules { modules = [ application.module ]; }) options;
+            #   #     # };
+            #   #     # # error: The option `deployments.baz.application-configuration.foo._module.freeformType' in `lib/modules.nix' is already declared in `data-model.nix'.
+            #   #     # # n.b. `_module.freeformType` is an option set in `evalModules`.
+            #   #     # type = submodule {
+            #   #     #   inherit (import "${sources.nixpkgs}/nixos" { configuration = application.module; }) options;
+            #   #     # };
+            #   #   })
+            #   #   (removeAttrs (config.applications) [ "_module" ]);
+            # };
           };
           runtime-environment = mkOption {
             description = "The run-time environment to deploy to";