updated the spec text

Author: PascalSenn

spec/Appendix A -- Field Selection.md

@@ -395,12 +395,20 @@ SelectedValueEntry ::
 - Path SelectedListValue
 - SelectedObjectValue
 
-A {SelectedValue} is defined as either a {Path} or a {SelectedObjectValue}
-
-A {Path} is designed to point to only a single value, although it may reference
-multiple fields depending on the return type. To allow selection from different
-paths based on type, a {Path} can include multiple paths separated by a pipe
-(`|`).
+A {SelectedValue} consists of one or more {SelectedValueEntry} components, which
+may be joined by a pipe (`|`) operator to indicate alternative selections based
+on type.
+
+Each {SelectedValueEntry} may take one of the following forms:
+
+- A {Path} (when not immediately followed by a dot) that is designed to point to
+  a single value, although it may reference multiple fields depending on its
+  return type.
+- A {Path} immediately followed by a dot and a {SelectedObjectValue} to denote a
+  nested object selection.
+- A {Path} immediately followed by a {SelectedListValue} to denote selection
+  from a list.
+- A standalone {SelectedObjectValue} 
 
 In the following example, the value could be `title` when referring to a `Book`
 and `movieTitle` when referring to a `Movie`.