diff --git a/api_analysis/lib/r4/shape-format.md b/api_analysis/lib/r4/shape-format.md
index 4d367723..e4445ce5 100644
--- a/api_analysis/lib/r4/shape-format.md
+++ b/api_analysis/lib/r4/shape-format.md
@@ -1,6 +1,6 @@
 # Proposal for package shape format
 
-Idea:
+## Idea
  * Use lists of stuff, let the index in the list act as an ID number. Then we
    can just reference the ID number when we reference the thing.
  * Include:
@@ -11,10 +11,224 @@ Idea:
  * Exclude:
    * Return types and argument types (maybe we add this later?)
 
-Undecided: (added in draft 2)
-   * Imports
-   * "extends" and "mixin"
-   * "implements"
+## Undecided
+### Imports
+See draft 1 -> draft 2.
+
+### `extends` and `mixin`
+See draft 1 -> draft 2.
+
+### `implements`
+See draft 1 -> draft 2.
+
+### Top-level member list
+We could collect all the member shapes (defined across all libraries), and store them all together in one list. We could then refer to the members exported in a given library by their indexes in this list.
+
+This can also allow us to no longer store `.identifiers` of shapes defined and exported in the same package, but note that we still need to record identifiers of any exported external top-level members, since we cannot produce summaries of them.
+
+#### Example
+
+In this example, we encode the member index as a tuple, where the first element is 0 if the member being exported has been defined in this package, and 1 if it is an external member.
+
+Alternatively, we can use one integer as an index, rolling over the count from `.members` into `.externalIdentifiers` (for example, in this case, the index of "Bar" would be 1, because `.members` contains 1 element).
+
+<details>
+<summary>Full example</summary>
+
+```js
+{
+  "verison": 1,
+  "package": "foo",
+  "version": "1.0.0",
+  // Shapes of top-level members defined in any library in this package.
+  "members": [
+    // This is the 0th top-level member defined in this package.
+    {
+      "name": "Foo",
+      "kind": "class",
+      "members": [
+        {
+          "name": "sayHello",
+          "kind": "method",
+          "params": [
+            {
+              "name": ...,
+              "kind": "positional" | "named",
+              "required": true | false,
+            },
+            ...
+          ],
+        },
+        ...
+      ],
+    },
+    ...
+  ],
+  // Identifiers of top-level members which are defined in a different package,
+  // but exported in this one.
+  "externalIdentifiers": [
+    // This is the 0th external top-level member.
+    "Bar"
+  ],
+  "libraries": [
+    // library 0:
+    {
+      "uri": "package:foo/foo.dart",
+      // Propogated exports, with this we can easily compute the set of exported
+      // members.
+      "exports": [
+        {
+          "library": 1, // library 1 is "package:foo/src/bar.dart"
+          "show": [            
+            [1, 0],     // the 0th external member is "Bar"
+          ],
+        },
+        {
+          "library": 2, // library 2 is "package:bar/bar.dart"
+          "hide": [
+            [0, 0],     // the 0th member defined in this package is "Foo"
+          ],
+        }
+      ],
+    },
+    // library 1:
+    {
+      "uri": "package:foo/src/bar.dart",
+      "exports": [
+        {
+          "id": 0, // library 0 is "package:foo/foo.dart"
+          "hide": [
+            [0, 0],     // the 0th member defined in this package is "Foo"
+          ],
+        },
+      ],
+    },
+    // library 2:
+    {
+      // TODO: Is this a good way to do external libraries?
+      "uri": "package:bar/bar.dart",
+      // We know nothing about external libraries, so there no data here.
+      // We have an entry in "libraries" such that they have an identifier.
+    },
+  ],
+}
+```
+</details>
+
+<details>
+<summary>Diff from draft 1</summary>
+
+```diff
+ {
+   "verison": 1,
+   "package": "foo",
+   "version": "1.0.0",
+-  "identifiers": [
+-    "Foo",        // 0
+-    "sayHello",   // 1
+-    "Bar",        // 2
++  // Shapes of top-level members defined in any library in this package.
++  "members": [
++    // This is the 0th top-level member defined in this package.
++    {
++      "name": "Foo",
++      "kind": "class",
++      "members": [
++        {
++          "name": "sayHello",
++          "kind": "method",
++          "params": [
++            {
++              "name": ...,
++              "kind": "positional" | "named",
++              "required": true | false,
++            },
++            ...
++          ],
++        },
++        ...
++      ],
++    },
++    ...
++  ],
++  // Identifiers of top-level members which are defined in a different package,
++  // but exported in this one.
++  "externalIdentifiers": [
++    // This is the 0th external top-level member.
++    "Bar"
+   ],
+   "libraries": [
+     // library 0:
+     {
+       "uri": "package:foo/foo.dart",
+       // Propogated exports, with this we can easily compute the set of exported
+       // members.
+       "exports": [
+         {
+           "library": 1, // library 1 is "package:foo/src/bar.dart"
+-          "show": [
+-            2,          // identifier 2 is "Bar"
++          "show": [            
++            [1, 0],     // the 0th external member is "Bar"
+           ],
+         },
+         {
+           "library": 2, // library 2 is "package:bar/bar.dart"
+           "hide": [
+-            0,          // identifier 0 is "Foo"
++            [0, 0],     // the 0th member defined in this package is "Foo"
+           ],
+         }
+       ],
+-      // Top-level things defined in the library
+-      // Not everything exported, this can be easily computed by using the
+-      // "exports" maps.
+-      "members": [
+-        {
+-          "name": 0     // identifier 0 is "Foo"
+-          "kind": "class",
+-          "members": [
+-            {
+-              "name": 1, // identifier 1 is "sayHello"
+-              "kind": "method",
+-              "params": [
+-                {
+-                  "name": ...,
+-                  "kind": "positional" | "named",
+-                  "required": true | false,
+-                },
+-                ...
+-              ],
+-            },
+-            ...
+-          ],
+-        },
+-      ],
+     },
+     // library 1:
+     {
+       "uri": "package:foo/src/bar.dart",
+       "exports": [
+         {
+           "id": 0, // library 0 is "package:foo/foo.dart"
+           "hide": [
+-            0,     // identifier 0 is "Foo"
++            [0, 0],     // the 0th member defined in this package is "Foo"
+           ],
+         },
+       ],
+     },
+     // library 2:
+     {
+       // TODO: Is this a good way to do external libraries?
+       "uri": "package:bar/bar.dart",
+       // We know nothing about external libraries, so there no data here.
+       // We have an entry in "libraries" such that they have an identifier.
+     },
+   ],
+ }
+```
+</details>
 
 ## Draft 1