relation type

2 files changed, 111 insertions, 1 deletions

diff --git a/lib/interop.ml b/lib/interop.ml
index 3b7a3d2..ea25e0c 100644
--- a/lib/interop.ml
+++ b/lib/interop.ml
@@ -1,7 +1,8 @@
 open Ctypes
 
 module Sha256 = struct
-  let compute_hash content =
+  type t = string
+  let compute_hash content: t =
     let size_with_null_terminator = C.Types.hash_size + 1 in
     let buf = Ctypes.allocate_n char ~count:size_with_null_terminator in
     let () = C.Functions.compute_hash buf (Bytes.to_string content) in
diff --git a/lib/relation.ml b/lib/relation.ml
new file mode 100644
index 0000000..f3f536a
--- /dev/null
+++ b/lib/relation.ml
@@ -0,0 +1,109 @@
+module Hash = struct
+  type t = Interop.Sha256.t
+
+  let compare = String.compare
+end
+
+module Name = struct
+  type t = string
+
+  let compare = String.compare
+end
+
+module Tree = struct
+  type t = unit
+end
+
+module Schema = struct
+  type t = (string, string) Hashtbl.t
+
+  let create () = Hashtbl.create 16
+end
+
+module RelationConstraints = struct
+  type t = (string * string) list
+end
+
+module Cardinality = struct
+  type t = Finite of int | AlephZero | Continuum
+end
+
+module Generator = struct
+  type result =
+    | Done
+    | Value of (string, string) Hashtbl.t * t
+    | Error of string
+
+  and t = (string, string) Hashtbl.t -> result
+end
+
+module MembershipCriteria = struct
+  type t = (string, string) Hashtbl.t
+
+  let create () = Hashtbl.create 16
+end
+
+module Provenance = struct
+  type t =
+    | Undefined
+    | Base of Name.t
+    | Join of t * t
+    | Select of t * MembershipCriteria.t
+    | Project of t * string list
+    | Take of t * int
+end
+
+module Lineage = struct
+  type t =
+    | Base of Name.t
+    | Select of (string -> bool) * t
+    | Project of string list * t
+    | Join of string * t * t
+    | ThetaJoin of (string -> string -> bool) * t * t
+    | Sort of (string -> string -> int) * t
+    | Take of int * t
+    | Aggregate of string * string * t
+end
+
+type t = {
+  hash : Hash.t;
+  name : Name.t;
+  tree : Tree.t option;
+  schema : Schema.t;
+  constraints : RelationConstraints.t;
+  cardinality : Cardinality.t;
+  generator : Generator.t option;
+  membership_criteria : MembershipCriteria.t;
+  provenance : Provenance.t;
+  lineage : Lineage.t;
+}
+
+let make ~hash ~name ~tree ~schema ~constraints ~cardinality ~generator
+    ~membership_criteria ~provenance ~lineage =
+  {
+    hash;
+    name;
+    tree;
+    schema;
+    constraints;
+    cardinality;
+    generator;
+    membership_criteria;
+    provenance;
+    lineage;
+  }
+
+let compare left right =
+  match Name.compare left.name right.name with
+  | 0 -> Hash.compare left.hash right.hash
+  | n -> n
+
+module Ord = struct
+  type nonrec t = t
+
+  let compare = compare
+end
+
+module Set = Set.Make (Ord)
+module Map = Map.Make (Ord)
+