1 files changed, 26 insertions, 0 deletions
diff --git a/lib/concepts/Mode.mli b/lib/concepts/Mode.mli
new file mode 100644
index 0000000..57b079f
--- /dev/null
+++ b/lib/concepts/Mode.mli
@@ -0,0 +1,26 @@
+type attribute = string
+type attributes = BatSet.String.t
+
+(** what asking a relation under a given set of bound attributes
+    affords. The answer is to whether anything satisfies the binding,
+    or the bindings of the attributes left free together with the
+    class of what is produced. *)
+type affordance = Decides | Generates of Cardinality.t
+
+type mode = {bound: attributes; affords: affordance}
+type t
+
+val attributes_of_list : attribute list -> attributes
+val decides_when : attribute list -> mode
+val generates_when : attribute list -> Cardinality.t -> mode
+val enumerable : Cardinality.t -> mode
+val empty : t
+val declare : mode -> t -> t
+val of_list : mode list -> t
+val to_list : t -> mode list
+
+(** the tightest class declared for generating under [bound]. A mode
+    declared for fewer bound attributes applies to more, since the
+    attributes left free are then fewer and no more numerous. *)
+val generation : t -> attributes -> Cardinality.t option
+val decision : t -> attributes -> bool