relation references as a term kind, written #Name

1 files changed, 9 insertions, 0 deletions

diff --git a/lib/term.mli b/lib/term.mli
index cf79d89..8dc201e 100644
--- a/lib/term.mli
+++ b/lib/term.mli
@@ -17,6 +17,11 @@ type t = private
           its minimal shape, so integer membership inclusion holds
           literally. *)
   | String of string
+  | Reference of string
+      (** A relation reference, written [#Name]: a first-class
+          value denoting a relation by name, resolved through the
+          catalog of a state. Distinct from {!String} on purpose;
+          identity is not representation. *)
   | Nil  (** The empty sequence, written [#()]. *)
   | Record of t Label.Map.t
       (** A nonempty labeled tuple. Attribute order is canonical
@@ -30,6 +35,10 @@ val nil : t
 (** The empty sequence, [#()]. The distinguished base every
     {!sequence} chain ends in. *)
 
+val reference : string -> (t, [ `Invalid_reference of string ]) result
+(** A relation reference. Validates the name: a letter, then
+    letters, digits, or underscores. *)
+
 val rational : num:Z.t -> den:Z.t -> (t, [ `Zero_denominator ]) result
 (** Normalizes on entry: reduces by the gcd, moves the sign to the
     numerator, and collapses to {!Integer} when the reduced