diff --git a/doc/interfaces/supercomputer_data/drafts/20231009_region_hierarchy/index.md b/doc/interfaces/supercomputer_data/drafts/20231009_region_hierarchy/index.md
index 3df31b47..74702a79 100644
--- a/doc/interfaces/supercomputer_data/drafts/20231009_region_hierarchy/index.md
+++ b/doc/interfaces/supercomputer_data/drafts/20231009_region_hierarchy/index.md
@@ -69,10 +69,102 @@ Sub regions fall in to a hierarchy, for example one HUC2 has many HUC4s.
 ## Examples
 
 <details>
-<summary>`region_hierarchy.json`</summary>
-I believe this example doesn't quite fit with the specification outline above yet, it's
-just an early draft.
+<summary>`root_regions.json`</summary>
+```{.json include="root_regions.json"}
+```
+</details>
+
+<details>
+<summary>`region_26000.json`</summary>
+```{.json include="region_26000.json"}
+```
+</details>
+
+<details>
+<summary>`region_26101.json`</summary>
+```{.json include="region_26101.json"}
+```
+</details>
+
+<details>
+<summary>`region_hierarchy_26000.json`</summary>
+```{.json include="region_hierarchy_26000.json"}
+```
+</details>
 
-```{.json include="regions.json"}
+<details>
+<summary>`region_hierarchy_26101.json`</summary>
+```{.json include="region_hierarchy_26101.json"}
 ```
 </details>
+
+
+## Notes
+
+I feel that we'll need a dedicated specification for the categorization of regions. E.g.
+
+`region_category_26000.json`
+```json
+{
+  "HUC2": {"long-name": "Hydrologic Unit Code (2-digit)"},
+  "USSTATE": {"long-name": "U.S. State"}
+}
+```
+
+and the hierarchy can define regions as members of categories instead of assigning
+regions to categories as an attribute of a region. e.g.:
+
+`region_hierarchy_26000.json`
+```json
+{
+  "HUC2": {
+    "children": {
+      "123123": {
+        "name": "HUC10",
+        "children": {
+          "HUC4": {
+            "234234": {
+              "name": "HUC1010",
+              "children": {
+                "HUC6": {
+                  "345345": {
+                    "name": "HUC101010"
+                  },
+                  "345346": {
+                    "name": "HUC101011"
+                  },
+                  "345347": {
+                    "name": "HUC101012"
+                  }
+                }
+              }
+            },
+            "234234": {
+              "name": "HUC1011",
+              "children": {
+                "HUC6": {
+                  "445345": {
+                    "name": "HUC101110"
+                  },
+                  "445346": {
+                    "name": "HUC101111"
+                  },
+                  "445347": {
+                    "name": "HUC101112"
+                  }
+                }
+              }
+            }
+          }
+      }
+    }
+  }
+}
+```
+
+Here, top-level keys and keys that are members of `children` dicts are collection
+identifiers, e.g. `HUC2` corresponds to `Hydrologic Unit Code (2-digit)` from
+`region_category_26000.json`.
+
+Perhaps instead of `children`, `items` is a more conventional name for members of a
+collection?
diff --git a/doc/interfaces/supercomputer_data/drafts/20231009_region_hierarchy/regions.json b/doc/interfaces/supercomputer_data/drafts/20231009_region_hierarchy/regions.json
deleted file mode 100644
index a6264fa8..00000000
--- a/doc/interfaces/supercomputer_data/drafts/20231009_region_hierarchy/regions.json
+++ /dev/null
@@ -1,263 +0,0 @@
-{
-  "26000": {
-    "name": "Western United States",
-    "code": "USwest",
-    "subdivisionType": "adm0group",
-    "subregion_collections": {
-      "adm1": {
-        "name": "State / Country subdivision level 1",
-        "code": "adm1",
-        "items": {
-          "11725": {
-            "name": "California",
-            "code": "US-CA",
-            "subdivisionType": "adm1",
-            "subregion_collections": {}
-          },
-          "11726": {
-            "name": "Colorado",
-            "code": "US-CO",
-            "subdivisionType": "adm1",
-            "subregion_collections": {}
-          }
-        }
-      },
-      "huc2": {
-        "name": "U.S. Hydrologic Unit Code level 2",
-        "code": "huc2",
-        "items": {
-          "12516": {
-            "name": "Pacific Northwest",
-            "code": "HUC17",
-            "subdivisionType": "huc2",
-            "subregion_collections": {
-              "huc4": {
-                "name": "U.S. Hydrologic Unit Code level 4",
-                "code": "huc4",
-                "items": {
-                  "12807": {
-                    "name": "Lower Columbia",
-                    "code": "HUC1708",
-                    "subdivisionType": "huc4",
-                    "subregion_collections": {}
-                  },
-                  "12809": {
-                    "name": "Oregon-Washington Coastal",
-                    "code": "HUC1710",
-                    "subdivisionType": "huc4",
-                    "subregion_collections": {}
-                  }
-                }
-              }
-            }
-          },
-          "12517": {
-            "name": "California",
-            "code": "HUC18",
-            "subdivisionType": "huc2",
-            "subregion_collections": {
-              "huc4": {
-                "name": "U.S. Hydrologic Unit Code level 4",
-                "code": "huc4",
-                "items": {
-                  "12815": {
-                    "name": "San Joaquin",
-                    "code": "HUC1804",
-                    "subdivisionType": "huc4",
-                    "subregion_collections": {}
-                  }
-                }
-              }
-            }
-          }
-        }
-      }
-    }
-  },
-  "26002": {
-    "name": "ASHimalayas",
-    "code": "ASHimalayas",
-    "subdivisionType": "adm0group",
-    "subregion_collections": {}
-  },
-  "26004": {
-    "name": "AMAndes",
-    "code": "AMAndes",
-    "subdivisionType": "adm0group",
-    "subregion_collections": {
-      "adm0": {
-        "name": "Country",
-        "code": "adm0",
-        "items": {
-          "2044": {
-            "name": "Chile",
-            "code": "CHL",
-            "subdivisionType": "adm0",
-            "subregion_collections": {
-              "adm1": {
-                "name": "State / Country subdivision level 1",
-                "code": "adm1",
-                "items": {
-                  "3908": {
-                    "name": "Libertador General Bernardo O'Higgins",
-                    "code": "CL-LI",
-                    "subdivisionType": "adm1",
-                    "subregion_collections": {}
-                  }
-                }
-              }
-            }
-          }
-        }
-      },
-      "hydro3": {
-        "name": "Hydrosheds level 3",
-        "code": "hydro3",
-        "items": {
-          "15235": {
-            "name": "South Chile coast",
-            "code": "HYD661",
-            "subdivisionType": "hydro3",
-            "subregion_collections": {
-              "hydro4": {
-                "name": "Hydrosheds level 4",
-                "code": "hydro4",
-                "items": {
-                  "17138": {
-                    "name": "Beagle channel",
-                    "code": "HYD6610",
-                    "subdivisionType": "hydro4",
-                    "subregion_collections": {
-                      "hydro5": {
-                        "name": "Hydrosheds level 5",
-                        "code": "hydro5",
-                        "subregion_collections": {
-                          "24134": {
-                            "name": "",
-                            "code": "HYD66100",
-                            "subdivisionType": "hydro5"
-                          }
-                        }
-                      }
-                    }
-                  }
-                }
-              }
-            }
-          }
-        }
-      }
-    }
-  },
-  "26100": {
-    "name": "USAlaskaWAleutian",
-    "code": "USAlaskaWAleutian",
-    "subdivisionType": "adm1part",
-    "subregion_collections": {
-      "huc2": {
-        "name": "U.S. Hydrologic Unit Code level 2",
-        "code": "huc2",
-        "items": {
-          "12518": {
-            "name": "Alaska",
-            "code": "HUC19",
-            "subdivisionType": "huc2",
-            "subregion_collections": {
-              "huc4": {
-                "name": "U.S. Hydrologic Unit Code level 4",
-                "code": "huc4",
-                "items": {
-                  "12825": {
-                    "name": "Northwest Alaska",
-                    "code": "HUC1905",
-                    "subdivisionType": "huc4",
-                    "subregion_collections": {
-                      "huc6": {
-                        "name": "U.S. Hydrologic Unit Code level 6",
-                        "code": "huc6",
-                        "subregion_collections": {
-                          "13355": {
-                            "name": "Kobuk-Selawik Rivers",
-                            "code": "HUC190503",
-                            "subdivisionType": "huc6"
-                          },
-                          "13368": {
-                            "name": "Norton Sound",
-                            "code": "HUC190501",
-                            "subdivisionType": "huc6"
-                          }
-                        }
-                      }
-                    }
-                  }
-                }
-              }
-            }
-          }
-        }
-      }
-    }
-  },
-  "26101": {
-    "name": "AMCanadaW",
-    "code": "AMCanadaW",
-    "subdivisionType": "adm0part",
-    "subregion_collections": {
-      "adm1": {
-        "name": "State / Country subdivision level 1",
-        "code": "adm1",
-        "items": {
-          "3701": {
-            "name": "Alberta",
-            "code": "CA-AB",
-            "subdivisionType": "adm1",
-            "subregion_collections": {}
-          }
-        }
-      },
-      "hydro3": {
-        "name": "Hydrosheds level 3",
-        "code": "hydro3",
-        "items": {
-          "15269": {
-            "name": "",
-            "code": "HYD782",
-            "subdivisionType": "hydro3",
-            "subregion_collections": {
-              "hydro4": {
-                "name": "Hydrosheds level 4",
-                "code": "hydro4",
-                "items": {
-                  "17376": {
-                    "name": "",
-                    "code": "HYD7821",
-                    "subdivisionType": "hydro4",
-                    "subregion_collections": {}
-                  },
-                  "17381": {
-                    "name": "",
-                    "code": "HYD7826",
-                    "subdivisionType": "hydro4",
-                    "subregion_collections": {
-                      "hydro5": {
-                        "name": "Hydrosheds level 5",
-                        "code": "hydro5",
-                        "subregion_collections": {
-                          "24989": {
-                            "name": "",
-                            "code": "HYD78268",
-                            "subdivisionType": "hydro5"
-                          }
-                        }
-                      }
-                    }
-                  }
-                }
-              }
-            }
-          }
-        }
-      }
-    }
-  }
-}