+/**
+ * Create a tuples with given values.
+ */
+extern tuple *tuple_create(int arity,...);
+
+/**
+ * Create a tuples with given values.
+ */
+extern tupleschema *tupleschema_create(int arity,tuple *columns);
+
+/**
+ * Copy the given tupleschema into a new tupleschema with some columns
+ * masked. This represents a sub-index type using the unmasked columns
+ * for indexing.
+ */
+extern tupleschema *tupleschema_mask(tupleschema *schema,...);
+