diff --git a/scopes/core/core.py b/scopes/core/core.py
index 50affe8..248a71a 100644
--- a/scopes/core/core.py
+++ b/scopes/core/core.py
@@ -2,21 +2,33 @@
 
 """The scopes.core package"""
 
+from __future__ import annotations  # no check of type annotations at runtime
 import asyncio
-from dataclasses import dataclass
-from types import CoroutineType, FunctionType
+from collections.abc import AsyncGenerator, Callable, Coroutine
+from dataclasses import dataclass, field
 from typing import Any
 
+from scopes.core.message import Message
 from scopes.util import keywords as k, Symbol
 
+type Proc = Callable[[Scope, Message], AsyncGenerator[Scope]]
+type Program = Callable[[Scope], Proc]
+type Syn = Callable[[Message], Message]
+
+async def proc_dummy(scope: Scope, msg: Message) -> AsyncGenerator[Scope]:
+    yield scope
+
 @dataclass
 class Scope:
 
     value: Any = 0
     categ: tuple[Symbol, Symbol] = (k.csys, k.c00)
     stage: Symbol = k.initial
-    proc: CoroutineType | None = None
-    program: dict[tuple[Symbol, Symbol], CoroutineType] = {}
-    syns: list[FunctionType] = []
-    environ: asyncio.Queue | None = None
+    proc: Proc = proc_dummy
+    program: Program = lambda x: proc_dummy
+    syns: list[Syn] = field(default_factory=list)
+    environ: asyncio.Queue = field(default_factory=asyncio.Queue)
 
+    def set_proc(self) -> Scope:
+        self.proc = self.program(self)
+        return self