{-# LANGUAGE DeriveDataTypeable #-}

{- |

Module : $Header$

Copyright : Francisc-Nicolae Bungiu, Jacobs University Bremen

License : GPLv2 or higher, see LICENSE.txt

RDF signature and sentences

-}

module RDF.Sign where

import RDF.AS

import Common.Result

import Data.Data

import qualified Data.Set as Set

data Sign = Sign

{ subjects :: Set.Set Term

, predicates :: Set.Set Term

, objects :: Set.Set Term

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

emptySign :: Sign

emptySign = Sign

{ subjects = Set.empty

, predicates = Set.empty

, objects = Set.empty

}

diffSig :: Sign -> Sign -> Sign

diffSig a b =

a { subjects = subjects a `Set.difference` subjects b

, predicates = predicates a `Set.difference` predicates b

, objects = objects a `Set.difference` objects b

}

addSign :: Sign -> Sign -> Sign

addSign toIns totalSign = totalSign

{ subjects = Set.union (subjects totalSign) (subjects toIns)

, predicates = Set.union (predicates totalSign) (predicates toIns)

, objects = Set.union (objects totalSign) (objects toIns)

}

isSubSign :: Sign -> Sign -> Bool

isSubSign a b =

Set.isSubsetOf (subjects a) (subjects b)

&& Set.isSubsetOf (predicates a) (predicates b)

&& Set.isSubsetOf (objects a) (objects b)

uniteSign :: Sign -> Sign -> Result Sign

uniteSign s1 s2 = return $ addSign s1 s2

symOf :: Sign -> Set.Set RDFEntity

symOf s = Set.unions

[ Set.map (RDFEntity SubjectEntity) $ subjects s

, Set.map (RDFEntity PredicateEntity) $ predicates s

, Set.map (RDFEntity ObjectEntity) $ objects s ]