document whole-set scheduling

README.md

@@ -33,7 +33,7 @@ The structure is flexible and is not limited to reading plans. Attainly can be u
 
 When creating a schedule, the user selects:
 
-* The collection or portion they want to complete
+* The set they want to complete
 * The level of the collection to schedule
 * The start date
 * The target completion date
@@ -47,6 +47,10 @@ For example, a user could choose to schedule:
 * Smaller sections within each chapter
 * Any other available level in the collection structure
 
+Schedules always cover a whole set. To schedule only a subset of an existing
+set, the user creates a separate set containing that subset and gives it its
+own name.
+
 ## Daily Progress
 
 Users can view the items scheduled for each day and mark them complete as they finish them.

ai/shared.md

@@ -9,6 +9,9 @@ these rules.
 - Attainly is in early development.
 - Attainly helps users break hierarchical goals into scheduled assignments,
   complete daily work, and track progress toward a target date.
+- Schedules target whole sets. Users choose an element kind as the assignment
+  granularity. To schedule a subset, create a separate named set containing
+  that subset.
 - Schedule recalculation must preserve completed work while redistributing
   unfinished assignments across the remaining dates.
 - Planned features in `README.md` are future ideas, not authorized scope.