Portability  FlexibleInstances, OverloadedStrings, TypeSynonymInstances 

Stability  experimental 
Maintainer  Douglas Burke 
Safe Haskell  None 
This module defines functions for representing and manipulating query binding variable sets. This is the key data that mediates between query and back substitution when performing inferences. A framework of query variable modifiers is provided that can be used to implement richer inferences, such as filtering of query results, or replacing values based on known relationships.
 data VarBinding a b = VarBinding {}
 nullVarBinding :: VarBinding a b
 boundVars :: (Ord a, Ord b) => VarBinding a b > Set a
 subBinding :: (Ord a, Ord b) => VarBinding a b > VarBinding a b > Bool
 makeVarBinding :: (Ord a, Ord b) => [(a, b)] > VarBinding a b
 applyVarBinding :: VarBinding a a > a > a
 joinVarBindings :: (Ord a, Ord b) => VarBinding a b > VarBinding a b > VarBinding a b
 addVarBinding :: (Ord a, Ord b) => a > b > VarBinding a b > VarBinding a b
 data VarBindingModify a b = VarBindingModify {
 vbmName :: ScopedName
 vbmApply :: [VarBinding a b] > [VarBinding a b]
 vbmVocab :: [a]
 vbmUsage :: [[a]]
 type OpenVarBindingModify lb vn = [lb] > VarBindingModify lb vn
 openVbmName :: OpenVarBindingModify lb vn > ScopedName
 vbmCompatibility :: Eq a => VarBindingModify a b > [a] > Maybe [a]
 vbmCompose :: Eq a => VarBindingModify a b > VarBindingModify a b > Maybe (VarBindingModify a b)
 composeSequence :: Eq a => [VarBindingModify a b] > Maybe (VarBindingModify a b)
 findCompositions :: Eq a => [VarBindingModify a b] > [a] > [VarBindingModify a b]
 findComposition :: Eq a => [VarBindingModify a b] > [a] > Maybe (VarBindingModify a b)
 data VarBindingFilter a b = VarBindingFilter {
 vbfName :: ScopedName
 vbfVocab :: [a]
 vbfTest :: VarBinding a b > Bool
 makeVarFilterModify :: VarBindingFilter a b > VarBindingModify a b
 makeVarTestFilter :: ScopedName > (b > Bool) > a > VarBindingFilter a b
 makeVarCompareFilter :: ScopedName > (b > b > Bool) > a > a > VarBindingFilter a b
 varBindingId :: VarBindingModify a b
 nullVarBindingModify :: OpenVarBindingModify a b
 varFilterDisjunction :: Eq a => [VarBindingFilter a b] > VarBindingFilter a b
 varFilterConjunction :: Eq a => [VarBindingFilter a b] > VarBindingFilter a b
 varFilterEQ :: Eq b => a > a > VarBindingFilter a b
 varFilterNE :: Eq b => a > a > VarBindingFilter a b
Documentation
data VarBinding a b Source
VarBinding is the type of an arbitrary variable bindings value, where the type of the bound values is not specified.
(Ord a, Ord b) => Eq (VarBinding a b)  The Eq instance is defined as the set equivalence of the pairs of variables in the binding. 
(Ord a, Ord b) => Ord (VarBinding a b)  The Ord instance is defined only on the pairs of variables in the binding. 
(Show a, Show b) => Show (VarBinding a b)  The Show instance only displays the pairs of variables in the binding. 
(Ord a, Ord b) => Monoid (VarBinding a b)  When combining instances, if there is an overlapping binding then the value from the first instance is used. 
nullVarBinding :: VarBinding a bSource
The null, or empry, binding maps no query variables.
This is the mempty
instance of the Monoid.
boundVars :: (Ord a, Ord b) => VarBinding a b > Set aSource
Return a list of the variables bound by a supplied variable binding
subBinding :: (Ord a, Ord b) => VarBinding a b > VarBinding a b > BoolSource
VarBinding subset function, tests to see if one query binding is a subset of another; i.e. every query variable mapping defined by one is also defined by the other.
makeVarBinding :: (Ord a, Ord b) => [(a, b)] > VarBinding a bSource
Function to make a variable binding from a list of pairs of variable and corresponding assigned value.
applyVarBinding :: VarBinding a a > a > aSource
Apply query binding to a supplied value, returning the value unchanged if no binding is defined
joinVarBindings :: (Ord a, Ord b) => VarBinding a b > VarBinding a b > VarBinding a bSource
Join a pair of query bindings, returning a new binding that maps all variables recognized by either of the input bindings. If the bindings should overlap, such overlap is not detected and the value from the first binding provided is used.
addVarBinding :: (Ord a, Ord b) => a > b > VarBinding a b > VarBinding a bSource
Add a single new value to a variable binding and return the resulting new variable binding.
data VarBindingModify a b Source
Define the type of a function to modify variable bindings in
forward chaining based on rule antecedent matches. This
function is used to implement the "allocated to" logic described
in Appendix B of the RDF semantics document, in which a specific
blank node is associated with all matches of some specific value
by applications of the rule on a given graph.
Use id
if no modification of the variable bindings is required.
This datatype consists of the modifier function itself, which operates on a list of variable bindings rather than a single variable binding (because some modifications share context across a set of bindings), and some additional descriptive information that allows possible usage patterns to be analyzed.
Some usage patterns (see vbmUsage
for more details):
 filter
 all variables are input variables, and the effect
of the modifier function is to drop variable bindings that
don't satisfy some criterion.
Identifiable by an empty element in
vbmUsage
.  source
 all variables are output variables: a raw query
could be viewed as a source of variable bindings.
Identifiable by an element of
vbmUsage
equal tovbmVocab
.  modifier
 for each supplied variable binding, one or more
new variable bindings may be created that contain the
input variables bound as supplied plus some additional variables.
Identifiable by an element of
vbmUsage
some subset ofvbmVocab
.
A variety of variable usage patterns may be supported by a given
modifier: a modifier may be used to define new variable bindings
from existing bindings in a number of ways, or simply to check that
some required relationship between bindings is satisfied.
(Example, for a + b = c
, any one variable can be deduced from the
other two, or all three may be supplied to check that the relationship
does indeed hold.)
VarBindingModify  

Show (OpenVarBindingModify a b)  Displays the name of the modifier. 
type OpenVarBindingModify lb vn = [lb] > VarBindingModify lb vnSource
Type for variable binding modifier that has yet to be instantiated with respect to the variables that it operates upon.
openVbmName :: OpenVarBindingModify lb vn > ScopedNameSource
Extract variable binding name from OpenVarBindingModify
value
(Because only the name is required, the application to an undefined list of variable labels should never be evaluated, as long as the name is not dependent on the variable names in any way.)
NOT QUITE... some of the functions that create OpenVarBindingModify
instances also patternmatch the number of labels provided, forcing
evaluation of the labels parameter, even though it's not used.
vbmCompatibility :: Eq a => VarBindingModify a b > [a] > Maybe [a]Source
Variable binding modifier compatibility test.
Given a list of bound variables and a variable binding modifier, return
a list of new variables that may be bound, or Nothing
.
Note: if the usage pattern component is wellformed (i.e. all elements different) then at most one element can be compatible with a given input variable set.
vbmCompose :: Eq a => VarBindingModify a b > VarBindingModify a b > Maybe (VarBindingModify a b)Source
Compose variable binding modifiers.
Returns Just a
new variable binding modifier that corresponds to
applying the first supplied modifier and then applying the second
one, or Nothing
if the two modifiers cannot be compatibly composed.
NOTE: this function does not, in general, commute.
NOTE: if there are different ways to achieve the same usage, that usage is currently repeated in the result returned.
composeSequence :: Eq a => [VarBindingModify a b] > Maybe (VarBindingModify a b)Source
Compose sequence of variable binding modifiers.
findCompositions :: Eq a => [VarBindingModify a b] > [a] > [VarBindingModify a b]Source
Find all compatible compositions of a list of variable binding modifiers for a given set of supplied bound variables.
findComposition :: Eq a => [VarBindingModify a b] > [a] > Maybe (VarBindingModify a b)Source
Return Just a
compatible composition of variable binding modifiers
for a given set of supplied bound variables, or Nothing
if there
is no compatible composition
data VarBindingFilter a b Source
VarBindingFilter is a function type that tests to see if a query binding satisfies some criterion.
Queries often want to apply some kind of filter or condition to the variable bindings that are processed. In inference rules, it sometimes seems desirable to stipulate additional conditions on the things that are matched.
This function type is used to perform such tests. A number of simple implementations are included below.
VarBindingFilter  

makeVarFilterModify :: VarBindingFilter a b > VarBindingModify a bSource
Make a variable binding modifier from a variable binding filter value.
makeVarTestFilter :: ScopedName > (b > Bool) > a > VarBindingFilter a bSource
Make a variable test filter for a named variable using a supplied value testing function.
makeVarCompareFilter :: ScopedName > (b > b > Bool) > a > a > VarBindingFilter a bSource
Make a variable comparison filter for named variables using a supplied value comparison function.
varBindingId :: VarBindingModify a bSource
Variable binding modifier that returns exactly those variable bindings presented.
nullVarBindingModify :: OpenVarBindingModify a bSource
Null variable binding modifier
This is like varBindingId
except parameterized by some labels.
I think this is redundant, and should be eliminated.
varFilterDisjunction :: Eq a => [VarBindingFilter a b] > VarBindingFilter a bSource
This function composes a number of query binding filters into a composite filter that accepts any query binding that satisfies at least one of the component values.
varFilterConjunction :: Eq a => [VarBindingFilter a b] > VarBindingFilter a bSource
This function composes a number of query binding filters into a composite filter that accepts any query binding that satisfies all of the component values.
The same function could be achieved by composing the component filterbased modifiers, but this function is more convenient as it avoids the need to check for modifier compatibility.
varFilterEQ :: Eq b => a > a > VarBindingFilter a bSource
This function generates a query binding filter that ensures that two indicated query variables are mapped to the same value.
varFilterNE :: Eq b => a > a > VarBindingFilter a bSource
This function generates a query binding filter that ensures that two indicated query variables are mapped to different values.