Haskell Implementation of Faceted Values

Faceted values can be a very strong primitive for privacy sensitive values.

This implementation is inspired by Thomas H. Austin and Cormac Flanagan, "Multiple Facets for Dynamic Information Flow."

A faceted value is a triple consisting principal k and two values V_H, V_L, which write as:

< k ? V_H, V_L >.

Intuitively, this faceted value appeared as V_H to private observers that can view k's private data, and as V_L to other public observers.

Jeeves, a programming language for automatically enforcing privacy policies, is also based faceted values.

How to build

$ cabal update
$ cabal install --only-dependencies --enable-tests
$ cabal configure --enable-tests
$ cabal build
# for testing.
$ cabal test

How to use

please see test or examples.

or, test log could be useful to understand how-to easily.

Test suite spec: RUNNING...

Data.Faceted
  facete value can be declared in intuitive manner "(\x -> x > 0) ? 1 .: 0)"
    - its observation with context 0 should be 0.
    - its observation with context 1 should be 1.

  use (??) for nested facete value "(\x -> x <= 2) ?? ((\x -> x < 2) ? 1 .: 2) .: ((\x -> x < 4 ) ? 3 .: 4)"
    - its observation with context 1 should be 1.
    - its observation with context 2 should be 2.
    - its observation with context 3 should be 3.
    - its observation with context 4 should be 4.

  Functor: ((*3) `fmap` (\x -> x > 0) ? 1 .: 0)) should be equivalent with < (x > 0) ? 1*3 : 0*3>.
    - observation with context 0 should be 0.
    - observation with context 1 should be 3.

  Applicative: ((+) <$> ((\x -> 0 < x && x < 3) ? 1 .: 2) <*> ((\x -> 1 < x && x < 4) ? 4 .: 8))
  This computation adds two faceted values. So in this case, 4 patterns of results can be observed.
  The result should be equivalent with
    < (0 < x < 3) ? < (1 < x < 4) ? 1+4 : 1+8 >
                  : < (1 < x < 4) ? 2+4 : 2+8 >>
    - observation with context 1 should be 9  (= 1 + 8).
    - observation with context 2 should be 5  (= 1 + 4).
    - observation with context 3 should be 6  (= 2 + 4).
    - observation with context 4 should be 10 (= 2 + 8).

  Applicative Do:
   do a <- ((\x -> 0 < x && x < 3) ? 1 .: 2)
      b <- ((\x -> 1 < x && x < 4) ? 4 .: 8)
      return a + b
  should be equivalent with above.

    - observation with context 1 should be 9  (= 1 + 8).
    - observation with context 2 should be 5  (= 1 + 4).
    - observation with context 3 should be 6  (= 2 + 4).
    - observation with context 4 should be 10 (= 2 + 8).

  Bind: ((\x -> 0 < x && x < 3) ? 1 .: 2) >>= (\v -> ((\x -> 1 < x && x < 4) ? (v+4) .: (v+8))
  shoule be equivalent with
    < (0 < x < 3) ? < (1 < x < 4) ? 1+4 : 1+8 >
                  : < (1 < x < 4) ? 2+4 : 2+8 >>
    - observation with context 1 should be 9  (= 1 + 8).
    - observation with context 2 should be 5  (= 1 + 4).
    - observation with context 3 should be 6  (= 2 + 4).
    - observation with context 4 should be 10 (= 2 + 8).

  Do Syntax:
  do a <- ((\x -> 0 < x && x < 3) ? 1 .: 2)
     b <- ((\x -> 1 < x && x < 4) ? (a+4) .: (a+8))
     (\y -> y < 3) ? (10*b) .: (100*b)
  shoule be equivalent with
    < (0 < x < 3) ? < (1 < x < 4) ? <(y < 3)? 10*(1+4) : 100*(1+4)>
                                  : <(y < 3)? 10*(2+8) : 100*(2+8)>>
                  : < (1 < x < 4) ? <(y < 3)? 10*(2+4) : 100*(2+4)>
                                  : <(y < 3)? 10*(2+8) : 100*(2+8)>>
    - observation with context 1 should be 90   (= 10 * (1 + 8)).
    - observation with context 2 should be 50   (= 10 * (1 + 4)).
    - observation with context 3 should be 600  (= 100 * (2 + 4)).
    - observation with context 4 should be 1000 (= 100 * (2 + 8)).

Finished in 0.0016 seconds
24 examples, 0 failures
Test suite spec: PASS
Test suite logged to: dist/test/faceted-0.1.0.0-spec.log

Documents

haddoc is here.