added user documentation how M1 export scopes handle nodes and ids.

docs/reference/converter-lang.adoc

@@ -72,6 +72,25 @@ closure::
 Converts the listed nodes, all descendants, and all referenced nodes.
 We apply this strategy until we include all Annotation, Containment, and Reference targets. 
 
+
+.Inclusion of nodes and ids
+The following table lists for each scope whether we include the target node / target node's id into the conversion.
+Example: For _descendants_ scope, we include both the target node and the target id of annotations and children; we do not include the target node of references, but we do include the target id of references.
+
+NOTE: If a node is included in the conversion for any reason (e.g. explicitly listed), we include their id at all places it is targeted, even if the _scope_ would not cover it.
+Example: Assume we have node with id `a` containing node `b`, and `c` referring to both `a` and `b`.
+We export `c` with _closure_ scope.
+Now we mention `a` as parent of `b`, as both are included in the conversion. 
+|===
+|Scope |Annotations + Children |References |Parents
+
+|listed      |no / yes  |no / yes  |no / yes
+|descendants |yes / yes |no / yes  |no / yes
+|closure     |yes / yes |yes / yes |no / no
+
+|===
+
+
 === Import Instance from JSON
 Technical name: `ImportInstanceFromJson` / `MergingLionWeb2MpsConverter`