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  ______     ___     _    _      ___     _    _   
 /_____//   / _ \\  | \  / ||   / _ \\  | || | || 
 `____ `   | / \ || |  \/  ||  / //\ \\ | || | || 
 /___//    | \_/ || | .  . || |  ___  ||| \\_/ || 
 `__ `      \___//  |_|\/|_|| |_||  |_|| \____//  
 /_//       `---`   `-`  `-`  `-`   `-`   `---`   
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Text this: Preservation of integrity constraints in definite DATALOG programs