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(** Worlds: the store of relations, and the loader that builds the
standalone one.
Decision 4 of the integration document: the VM is parameterized
over a world. This module gives the module type every host
satisfies, the standalone in-memory world, and the loader that
admits a parsed program into it. Admission is where totality is
enforced: a program that gets a world is a program whose queries
terminate. *)
(** A compiled relational expression: what rule bodies and queries
are made of after names are resolved. *)
type expr =
| Apply of string * Pattern.t Label.Map.t
| And of expr * expr
| Or of expr * expr
type rule = {
rule_name : string;
head : Pattern.t Label.Map.t;
body : expr;
witness : Label.t option;
(** For a recursive rule, the label whose argument strictly
decreases. The VM requires it ground before unfolding,
which is what turns the admission proof into runtime
termination. [None] on non-recursive rules. *)
}
(** The builtin domains a schema may constrain an attribute by. *)
type domain = D_integer | D_natural | D_rational | D_string
(** How a relation is defined. *)
type def =
| Table of { schema : (Label.t * domain) list; facts : Term.t Label.Map.t list }
(** Extensional: a schema and finite stored tuples. *)
| Rules of rule list (** Intensional: defined by admitted rules. *)
(** What a host must answer for the VM to run: which relation lives
under a name. Builtins are the VM's own and are not consulted
here. *)
module type WORLD = sig
type t
val find : t -> string -> def option
end
type error
val pp_error : Format.formatter -> error -> unit
(** The standalone world: an immutable catalog loaded from program
text. This is Sol as a separate language; there are no branches,
no transitions, only the pure fragment. *)
module Standalone : sig
type t
val find : t -> string -> def option
val load : Ast.statement list -> (t * expr list, error) result
(** Admits a program: registers relations, checks every fact
against its schema and domains, compiles rules and queries,
and enforces totality. Rejected, not deferred: a recursive
rule without a structural decrease witness, a mutual
recursion cycle, an unknown relation, or an ill-typed fact is
an [error], and no world exists. Returns the world and the
query expressions in program order. *)
end
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