{-# LANGUAGE DeriveDataTypeable #-}

{- |

Module : $Header$

Description : data types for consistency aka conservativity

Copyright : (c) Christian Maeder, DFKI GmbH 2008

License : GPLv2 or higher, see LICENSE.txt

Maintainer : Christian.Maeder@dfki.de

Stability : provisional

Portability : portable

Data types for conservativity

-}

module Common.Consistency where

import Common.Doc

import Common.DocUtils

import Common.AS_Annotation

import Common.Result

import Data.Data

{- | Conservativity annotations. For compactness, only the greatest applicable

value is used in a DG. PCons stands for prooftheoretic conservativity as

required for extending imports (no confusion) in Maude -}

data Conservativity =

Inconsistent

| Unknown String

| None

| PCons

| Cons

| Mono

| Def

deriving (Show, Read, Eq, Ord, Typeable, Data)

showConsistencyStatus :: Conservativity -> String

showConsistencyStatus cs = case cs of

Inconsistent -> "not conservative"

Unknown str -> "unknown if being conservative. Cause is : " ++ str

None -> "unknown if being conservative"

Cons -> "conservative"

PCons -> "proof-theoretically conservative"

Mono -> "monomorphic"

Def -> "definitional"

instance Pretty Conservativity where

pretty = text . showConsistencyStatus

{- | All target sentences must be implied by the source translated

along the morphism. They are axioms only and not identical to any

translated sentence of the source. -}

data ConservativityChecker sign sentence morphism = ConservativityChecker

{ checkerId :: String

, checkerUsable :: IO (Maybe String)

, checkConservativity

:: (sign, [Named sentence])

-> morphism

-> [Named sentence]

-> IO (Result (Conservativity, [sentence])) }