Clarify child Dataset relationships

SPECIFICATION.md

@@ -114,7 +114,36 @@ Subsequently, all the remaining nodes are assigned a `@type` of either `Dataset`
 If a Dataset node has additional files, they should be listed in its `hasPart` property and can be referenced through their `@id`.
 All nodes with `@type: Dataset` SHOULD include `name`, `author` properties. Furthermore, other properties of `Dataset`, such as `identifier`, `dateCreated`, `dateModified`, `text`, `keywords`, `comment` MAY also be added.
 
-If a Dataset references other Datasets (_e.g._ a parent experiment with child experiments), they must also be present in the `hasPart` of `./` if they are meant to be imported. A Dataset MUST not contain other Datasets in its `hasPart` section.
+If a Dataset references child Datasets (_e.g._ a parent experiment with child experiments), it SHOULD list them in its `hasPart` section. Each child Dataset that is meant to be imported MUST also be listed directly in the `hasPart` of `./`; a reference from its parent alone does not mark it for import.
+
+For example, both the parent and child experiments below are meant to be imported, while the parent's `hasPart` also records their relationship:
+
+```json
+{
+  "@graph": [
+    {
+      "@id": "./",
+      "@type": "Dataset",
+      "hasPart": [
+        { "@id": "./parent/" },
+        { "@id": "./child/" }
+      ]
+    },
+    {
+      "@id": "./parent/",
+      "@type": "Dataset",
+      "hasPart": [
+        { "@id": "./child/" }
+      ]
+    },
+    {
+      "@id": "./child/",
+      "@type": "Dataset",
+      "hasPart": []
+    }
+  ]
+}
+```
 
 All nodes with `@type: File` SHOULD include `name`, `encodingFormat`, `contentSize` properties. Furthermore, other properties of `File`, such as `description`, `sha256`, `author`, `identifier`, `dateCreated`, `dateModified`, `text` MAY also be added.