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#!/usr/local/bin/python
# -*- coding: utf-8 -*-
"""
An implementation of the W3C SPARQL Algebra on top of sparql-p's expansion trees
See: http://www.w3.org/TR/rdf-sparql-query/#sparqlAlgebra
For each symbol in a SPARQL abstract query, we define an operator for evaluation.
The SPARQL algebra operators of the same name are used to evaluate SPARQL abstract
query nodes as described in the section "Evaluation Semantics".
We define eval(D(G), graph pattern) as the evaluation of a graph pattern with respect
to a dataset D having active graph G. The active graph is initially the default graph.
"""
import unittest, os
from StringIO import StringIO
from rdflib.Graph import Graph, ReadOnlyGraphAggregate, ConjunctiveGraph
from rdflib import URIRef, Variable, plugin, BNode, Literal
from rdflib.util import first
from rdflib.store import Store
from rdflib.sparql.bison.Query import AskQuery, SelectQuery, DescribeQuery, Query, Prolog
from rdflib.sparql.bison.IRIRef import NamedGraph,RemoteGraph
from rdflib.sparql.bison.SolutionModifier import ASCENDING_ORDER
from rdflib.sparql import sparqlGraph, sparqlOperators, SPARQLError, Query, DESCRIBE
from rdflib.sparql.bison.SPARQLEvaluate import unRollTripleItems, _variablesToArray
from rdflib.sparql.bison.GraphPattern import *
from rdflib.sparql.graphPattern import BasicGraphPattern
from rdflib.sparql.bison.Triples import ParsedConstrainedTriples
from rdflib.sparql.bison.SPARQLEvaluate import createSPARQLPConstraint,\
CONSTRUCT_NOT_SUPPORTED,convertTerm
#A variable to determine whether we obey SPARQL definition of RDF dataset
#which does not allow matching of default graphs (or any graph with a BNode for a name)
#"An RDF Dataset comprises one graph,
# the default graph, which does not have a name" -
# http://www.w3.org/TR/rdf-sparql-query/#namedAndDefaultGraph
DAWG_DATASET_COMPLIANCE = False
def ReduceGraphPattern(graphPattern,prolog):
"""
Takes parsed graph pattern and converts it into a BGP operator
.. Replace all basic graph patterns by BGP(list of triple patterns) ..
"""
if isinstance(graphPattern.triples[0],list) and len(graphPattern.triples) == 1:
graphPattern.triples = graphPattern.triples[0]
items = []
for triple in graphPattern.triples:
bgp=BasicGraphPattern(list(unRollTripleItems(triple,prolog)),prolog)
items.append(bgp)
if len(items) == 1:
assert isinstance(items[0],BasicGraphPattern), repr(items)
bgp=items[0]
return bgp
elif len(items) > 1:
constraints=[b.constraints for b in items if b.constraints]
constraints=reduce(lambda x,y:x+y,constraints,[])
def mergeBGPs(left,right):
if isinstance(left,BasicGraphPattern):
left = left.patterns
if isinstance(right,BasicGraphPattern):
right = right.patterns
return left+right
bgp=BasicGraphPattern(reduce(mergeBGPs,items),prolog)
bgp.addConstraints(constraints)
return bgp
else:
#an empty BGP?
raise
def ReduceToAlgebra(left,right):
"""
Converts a parsed Group Graph Pattern into an expression in the algebra by recursive
folding / reduction (via functional programming) of the GGP as a list of Basic
Triple Patterns or "Graph Pattern Blocks"
12.2.1 Converting Graph Patterns
[20] GroupGraphPattern ::= '{' TriplesBlock? ( ( GraphPatternNotTriples | Filter )
'.'? TriplesBlock? )* '}'
[22] GraphPatternNotTriples ::= OptionalGraphPattern | GroupOrUnionGraphPattern |
GraphGraphPattern
[26] Filter ::= 'FILTER' Constraint
[27] Constraint ::= BrackettedExpression | BuiltInCall | FunctionCall
[56] BrackettedExpression ::= '(' ConditionalOrExpression ')'
( GraphPatternNotTriples | Filter ) '.'? TriplesBlock?
nonTripleGraphPattern filter triples
"""
if not isinstance(right,AlgebraExpression):
if isinstance(right,ParsedGroupGraphPattern):
right = reduce(ReduceToAlgebra,right,None)
print right;raise
assert isinstance(right,GraphPattern),type(right)
#Parsed Graph Pattern
if right.triples:
if right.nonTripleGraphPattern:
#left is None, just return right (a GraphPatternNotTriples)
if isinstance(right.nonTripleGraphPattern,ParsedGraphGraphPattern):
right = Join(ReduceGraphPattern(right,prolog),
GraphExpression(
right.nonTripleGraphPattern.name,
reduce(ReduceToAlgebra,
right.nonTripleGraphPattern.graphPatterns,
None)))
elif isinstance(right.nonTripleGraphPattern,
ParsedOptionalGraphPattern):
# Join(LeftJoin( ..left.. ,{..}),..triples..)
if left:
assert isinstance(left,(Join,BasicGraphPattern)),repr(left)
rightTriples = ReduceGraphPattern(right,prolog)
LJright = LeftJoin(left,
reduce(ReduceToAlgebra,
right.nonTripleGraphPattern.graphPatterns,
None))
return Join(LJright,rightTriples)
else:
# LeftJoin({},right) => {}
#see http://lists.w3.org/Archives/Public/public-rdf-dawg/2007AprJun/0046.html
return EmptyGraphPatternExpression()
elif isinstance(right.nonTripleGraphPattern,
ParsedAlternativeGraphPattern):
#Join(Union(..),..triples..)
unionList =\
[ reduce(ReduceToAlgebra,i.graphPatterns,None) for i in
right.nonTripleGraphPattern.alternativePatterns ]
right = Join(reduce(Union,unionList),
ReduceGraphPattern(right,prolog))
else:
raise Exception(right)
else:
if isinstance(left,BasicGraphPattern) and left.constraints:
if right.filter:
if not left.patterns:
#{ } FILTER E1 FILTER E2 BGP(..)
filter2=createSPARQLPConstraint(right.filter,prolog)
right = ReduceGraphPattern(right,prolog)
right.addConstraints(left.constraints)
right.addConstraint(filter2)
return right
else:
#BGP(..) FILTER E1 FILTER E2 BGP(..)
left.addConstraint(createSPARQLPConstraint(right.filter,
prolog))
right = ReduceGraphPattern(right,prolog)
else:
if right.filter:
#FILTER ...
filter=createSPARQLPConstraint(right.filter,prolog)
right = ReduceGraphPattern(right,prolog)
right.addConstraint(filter)
else:
#BGP(..)
right = ReduceGraphPattern(right,prolog)
else:
#right.triples is None
if right.nonTripleGraphPattern is None:
if right.filter:
if isinstance(left,BasicGraphPattern):
#BGP(...) FILTER
left.addConstraint(createSPARQLPConstraint(right.filter,
prolog))
return left
else:
pattern=BasicGraphPattern()
pattern.addConstraint(createSPARQLPConstraint(right.filter,
prolog))
if left is None:
return pattern
else:
right=pattern
else:
raise Exception(right)
elif right.nonTripleGraphPattern:
if isinstance(right.nonTripleGraphPattern,ParsedGraphGraphPattern):
# Join(left,Graph(...))
right = GraphExpression(right.nonTripleGraphPattern.name,
reduce(ReduceToAlgebra,
right.nonTripleGraphPattern.graphPatterns,
None))
elif isinstance(right.nonTripleGraphPattern,ParsedOptionalGraphPattern):
if left:
# LeftJoin(left,right)
return LeftJoin(left,
reduce(ReduceToAlgebra,
right.nonTripleGraphPattern.graphPatterns,
None))
else:
# LeftJoin({},right)
#see - http://lists.w3.org/Archives/Public/public-rdf-dawg/2007AprJun/0046.html
return EmptyGraphPatternExpression()
elif isinstance(right.nonTripleGraphPattern,
ParsedAlternativeGraphPattern):
#right = Union(..)
unionList =\
map(lambda i: reduce(ReduceToAlgebra,i.graphPatterns,None),
right.nonTripleGraphPattern.alternativePatterns)
right = reduce(Union,unionList)
else:
raise Exception(right)
if not left:
return right
else:
return Join(left,right)
def RenderSPARQLAlgebra(parsedSPARQL,nsMappings=None):
nsMappings = nsMappings and nsMappings or {}
global prolog
prolog = parsedSPARQL.prolog
if prolog is not None:
prolog.DEBUG = False
else:
prolog = Prolog(None, [])
prolog.DEBUG=False
return reduce(ReduceToAlgebra,
parsedSPARQL.query.whereClause.parsedGraphPattern.graphPatterns,None)
def LoadGraph(dtSet,dataSetBase,graph):
#An RDF URI dereference, following TAG best practices
#Need a hook (4Suite) to bypass urllib's inability
#to implement URI RFC verbatim - problematic for descendent
#specifications
try:
from Ft.Lib.Uri import UriResolverBase as Resolver
from Ft.Lib.Uri import GetScheme, OsPathToUri
except:
def OsPathToUri(path):
return path
def GetScheme(uri):
return None
class Resolver:
supportedSchemas=[None]
def resolve(self, uriRef, baseUri):
return uriRef
if dataSetBase is not None:
res = Resolver()
scheme = GetScheme(dtSet) or GetScheme(dataSetBase)
if scheme not in res.supportedSchemes:
dataSetBase = OsPathToUri(dataSetBase)
source=Resolver().resolve(str(dtSet), dataSetBase)
else:
source = dtSet
#GRDDL hook here!
try:
#Try as RDF/XML first (without resolving)
graph.parse(source)
except:
try:
#Parse as Notation 3 instead
source=Resolver().resolve(str(dtSet), dataSetBase)
graph.parse(source,format='n3')
except:
raise
#RDFa?
graph.parse(dtSet,format='rdfa')
def TopEvaluate(query,dataset,passedBindings = None,DEBUG=False,exportTree=False,
dataSetBase=None,
extensionFunctions={}):
"""
The outcome of executing a SPARQL is defined by a series of steps, starting
from the SPARQL query as a string, turning that string into an abstract
syntax form, then turning the abstract syntax into a SPARQL abstract query
comprising operators from the SPARQL algebra. This abstract query is then
evaluated on an RDF dataset.
"""
if not passedBindings:
passedBindings = {}
global prolog
if query.prolog:
query.prolog.DEBUG = DEBUG
prolog = query.prolog
prolog.extensionFunctions.update(extensionFunctions)
if query.query.dataSets:
graphs = []
for dtSet in query.query.dataSets:
if isinstance(dtSet,NamedGraph):
newGraph = Graph(dataset.store,dtSet)
LoadGraph(dtSet,dataSetBase,newGraph)
graphs.append(newGraph)
else:
#"Each FROM clause contains an IRI that indicates a graph to be
# used to form the default graph. This does not put the graph
# in as a named graph." -- 8.2.1 Specifying the Default Graph
if DAWG_DATASET_COMPLIANCE:
#@@ this should indicate a merge into the 'default' graph
# per http://www.w3.org/TR/rdf-sparql-query/#unnamedGraph
# (8.2.1 Specifying the Default Graph)
assert isinstance(dataset,ConjunctiveGraph)
memGraph = dataset.default_context
else:
memStore = plugin.get('IOMemory',Store)()
memGraph = Graph(memStore)
LoadGraph(dtSet,dataSetBase,memGraph)
if memGraph.identifier not in [g.identifier for g in graphs]:
graphs.append(memGraph)
tripleStore = sparqlGraph.SPARQLGraph(ReadOnlyGraphAggregate(graphs,
store=dataset.store),
dSCompliance=DAWG_DATASET_COMPLIANCE)
else:
tripleStore = sparqlGraph.SPARQLGraph(dataset,
dSCompliance=DAWG_DATASET_COMPLIANCE)
if isinstance(query.query,SelectQuery) and query.query.variables:
query.query.variables = [convertTerm(item,query.prolog)
for item in query.query.variables]
else:
query.query.variables = []
expr = reduce(ReduceToAlgebra,query.query.whereClause.parsedGraphPattern.graphPatterns,
None)
if isinstance(expr,BasicGraphPattern):
retval = None
bindings = Query._createInitialBindings(expr)
if passedBindings:
bindings.update(passedBindings)
top = Query._SPARQLNode(None,bindings,expr.patterns, tripleStore,expr=expr)
top.expand(expr.constraints)
# for tree in Query._fetchBoundLeaves(top):
# print_tree(tree)
# print "---------------"
result = Query.Query(top, tripleStore)
else:
assert isinstance(expr,AlgebraExpression), repr(expr)
if DEBUG:
print "## Full SPARQL Algebra expression ##"
print expr
print "###################################"
result = expr.evaluate(tripleStore,passedBindings,query.prolog)
if isinstance(result,BasicGraphPattern):
retval = None
bindings = Query._createInitialBindings(result)
if passedBindings:
bindings.update(passedBindings)
top = Query._SPARQLNode(None,bindings,result.patterns,
result.tripleStore,expr=result)
top.expand(result.constraints)
result = Query.Query(top, tripleStore)
assert isinstance(result,Query.Query),repr(result)
if exportTree:
from rdflib.sparql.Visualization import ExportExpansionNode
if result.top:
ExportExpansionNode(result.top,fname='out.svg',verbose=True)
else:
ExportExpansionNode(result.parent1.top,fname='out1.svg',verbose=True)
ExportExpansionNode(result.parent2.top,fname='out2.svg',verbose=True)
if result == None :
# generate some proper output for the exception :-)
msg = "Errors in the patterns, no valid query object generated; "
msg += ("pattern:\n%s\netc..." % basicPatterns[0])
raise SPARQLError(msg)
if isinstance(query.query,AskQuery):
return result.ask()
elif isinstance(query.query,SelectQuery):
orderBy = None
orderAsc = None
if query.query.solutionModifier.orderClause:
orderBy = []
orderAsc = []
for orderCond in query.query.solutionModifier.orderClause:
# is it a variable?
if isinstance(orderCond,Variable):
orderBy.append(orderCond)
orderAsc.append(ASCENDING_ORDER)
# is it another expression, only variables are supported
else:
expr = orderCond.expression
assert isinstance(expr,Variable),\
"Support for ORDER BY with anything other than a variable is not supported: %s"%expr
orderBy.append(expr)
orderAsc.append(orderCond.order == ASCENDING_ORDER)
if query.query.solutionModifier.limitClause is not None:
limit = int(query.query.solutionModifier.limitClause)
else:
limit = None
if query.query.solutionModifier.offsetClause is not None:
offset = int(query.query.solutionModifier.offsetClause)
else:
offset = 0
topUnionBindings=[]
selection=result.select(query.query.variables,
query.query.distinct,
limit,
orderBy,
orderAsc,
offset
)
selectionF = Query._variablesToArray(query.query.variables,"selection")
if result.parent1 != None and result.parent2 != None :
topUnionBindings=reduce(lambda x,y:x+y,
[root.returnResult(selectionF) \
for root in fetchUnionBranchesRoots(result)])
else:
if (limit == 0 or limit is not None or offset is not None and \
offset > 0):
topUnionBindings=[]
else:
topUnionBindings=result.top.returnResult(selectionF)
return selection,\
_variablesToArray(query.query.variables,"selection"),\
result._getAllVariables(),\
orderBy,query.query.distinct,\
topUnionBindings
elif isinstance(query.query,DescribeQuery):
if query.query.solutionModifier.limitClause is not None:
limit = int(query.query.solutionModifier.limitClause)
else:
limit = None
if query.query.solutionModifier.offsetClause is not None:
offset = int(query.query.solutionModifier.offsetClause)
else:
offset = 0
if result.parent1 != None and result.parent2 != None :
rt=(r for r in reduce(lambda x,y:x+y,
[root.returnResult(selectionF) \
for root in fetchUnionBranchesRoots(result)]))
elif limit is not None or offset != 0:
raise NotImplemented("Solution modifiers cannot be used with DESCRIBE")
else:
rt=result.top.returnResult(None)
rtGraph=Graph()
for binding in rt:
g=extensionFunctions[DESCRIBE](query.query.describeVars,
binding,
tripleStore.graph)
return g
else:
# 10.2 CONSTRUCT
# The CONSTRUCT query form returns a single RDF graph specified by a graph
# template. The result is an RDF graph formed by taking each query solution
# in the solution sequence, substituting for the variables in the graph
# template, and combining the triples into a single RDF graph by set union.
if query.query.solutionModifier.limitClause is not None:
limit = int(query.query.solutionModifier.limitClause)
else:
limit = None
if query.query.solutionModifier.offsetClause is not None:
offset = int(query.query.solutionModifier.offsetClause)
else:
offset = 0
if result.parent1 != None and result.parent2 != None :
rt=(r for r in reduce(lambda x,y:x+y,
[root.returnResult(selectionF) \
for root in fetchUnionBranchesRoots(result)]))
elif limit is not None or offset != 0:
raise NotImplemented("Solution modifiers cannot be used with CONSTRUCT")
else:
rt=result.top.returnResult(None)
rtGraph=Graph()
for binding in rt:
for s,p,o,func in ReduceGraphPattern(query.query.triples,prolog).patterns:
s,p,o=map(lambda x:isinstance(x,Variable) and binding.get(x) or
x,[s,p,o])
#If any such instantiation produces a triple containing an unbound
#variable or an illegal RDF construct, such as a literal in subject
#or predicate position, then that triple is not included in the
#output RDF graph.
if not [i for i in [s,p,o] if isinstance(i,Variable)]:
rtGraph.add((s,p,o))
return rtGraph
class AlgebraExpression(object):
"""
For each symbol in a SPARQL abstract query, we define an operator for
evaluation. The SPARQL algebra operators of the same name are used
to evaluate SPARQL abstract query nodes as described in the section
"Evaluation Semantics".
"""
def __repr__(self):
return "%s(%s,%s)"%(self.__class__.__name__,self.left,self.right)
def evaluate(self,tripleStore,initialBindings,prolog):
"""
12.5 Evaluation Semantics
We define eval(D(G), graph pattern) as the evaluation of a graph pattern
with respect to a dataset D having active graph G. The active graph is
initially the default graph.
"""
raise Exception(repr(self))
class EmptyGraphPatternExpression(AlgebraExpression):
"""
A placeholder for evaluating empty graph patterns - which
should result in an empty multiset of solution bindings
"""
def __repr__(self):
return "EmptyGraphPatternExpression(..)"
def evaluate(self,tripleStore,initialBindings,prolog):
#raise NotImplementedError("Empty Graph Pattern expressions, not supported")
if prolog.DEBUG:
print "eval(%s,%s,%s)"%(self,initialBindings,tripleStore.graph)
empty = Query._SPARQLNode(None,{},[],tripleStore)
empty.bound = False
return Query.Query(empty, tripleStore)
def fetchUnionBranchesRoots(node):
for parent in [node.parent1,node.parent2]:
if parent.parent1:
for branch_root in fetchUnionBranchesRoots(parent):
yield branch_root
else:
yield parent.top
def fetchChildren(node):
if isinstance(node,Query._SPARQLNode):
yield [c for c in node.children]
elif isinstance(node,Query.Query):
if node.parent1 is None:
for c in fetchChildren(node.top):
yield c
else:
for parent in [node.parent1,node.parent2]:
for c in fetchChildren(parent):
yield c
def walktree(top, depthfirst = True, leavesOnly = True, optProxies=False):
#assert top.parent1 is None
if isinstance(top,Query._SPARQLNode) and top.clash:
return
if not depthfirst and (not leavesOnly or not top.children):
proxies=False
for optChild in reduce(lambda x,y: x+y,[list(Query._fetchBoundLeaves(o))
for o in top.optionalTrees],[]):
proxies=True
yield optChild
if not proxies:
yield top
children=reduce(lambda x,y:x+y,list(fetchChildren(top)))
# if isinstance(top,Query._SPARQLNode) or isinstance(top,Query.Query) and \
# top.parent1 is None:
# children = top.children
# else:
# children = top.parent1.children + top.parent2.children
for child in children:
if child.children:
for newtop in walktree(child, depthfirst,leavesOnly,optProxies):
yield newtop
else:
proxies=False
for optChild in reduce(lambda x,y: x+y,[list(Query._fetchBoundLeaves(o))
for o in child.optionalTrees],[]):
proxies=True
yield optChild
if not proxies:
yield child
if depthfirst and (not leavesOnly or not children):
proxies=False
for optChild in reduce(lambda x,y: x+y,[list(Query._fetchBoundLeaves(o))
for o in top.optionalTrees],[]):
proxies=True
yield optChild
if not proxies:
yield top
def print_tree(node, padding=' '):
print padding[:-1] + repr(node)
padding = padding + ' '
count = 0
#_children1=reduce(lambda x,y:x+y,list(fetchChildren(node)))
for child in node.children:#_children1:
count += 1
print padding + '|'
if child.children:
if count == len(node.children):
print_tree(child, padding + ' ')
else:
print_tree(child, padding + '|')
else:
print padding + '+-' + repr(child) + ' ' + repr(dict([(k,v)
for k,v in child.bindings.items() if v]))
optCount=0
for optTree in child.optionalTrees:
optCount += 1
print padding + '||'
if optTree.children:
if optCount == len(child.optionalTrees):
print_tree(optTree, padding + ' ')
else:
print_tree(optTree, padding + '||')
else:
print padding + '+=' + repr(optTree)
count = 0
for optTree in node.optionalTrees:
count += 1
print padding + '||'
if optTree.children:
if count == len(node.optionalTrees):
print_tree(optTree, padding + ' ')
else:
print_tree(optTree, padding + '||')
else:
print padding + '+=' + repr(optTree)
def _ExpandJoin(node,expression,tripleStore,prolog,optionalTree=False):
"""
Traverses to the leaves of expansion trees to implement the Join
operator
"""
if prolog.DEBUG:
print_tree(node)
print "-------------------"
#for node in BF_leaf_traversal(node):
currExpr = expression
for node in walktree(node):
if node.clash:
continue
assert len(node.children) == 0
if prolog.DEBUG:
print "Performing Join(%s,..)"%node
if isinstance(currExpr,AlgebraExpression):
#If an algebra expression evaluate it passing on the leaf bindings
if prolog.DEBUG:
print "passing on bindings to %s\n:%s"%(currExpr,node.bindings.copy())
expression = currExpr.evaluate(tripleStore,node.bindings.copy(),prolog)
else:
expression = currExpr
if isinstance(expression,BasicGraphPattern):
tS = tripleStore
if hasattr(expression,'tripleStore'):
if prolog.DEBUG:
print "has tripleStore: ",expression.tripleStore
tS = expression.tripleStore
if prolog.DEBUG:
print "Evaluated left node and traversed to leaf, expanding with ",
expression
print node.tripleStore.graph
print "expressions bindings: ",
Query._createInitialBindings(expression)
print "node bindings: ", node.bindings
exprBindings = Query._createInitialBindings(expression)
exprBindings.update(node.bindings)
#An indicator for whether this node has any descendant optional expansions
#we should consider instead
#in Join(LeftJoin(A,B),X), if the inner LeftJoin is successful,
#then X is joined
#against the cumulative bindings ( instead of just A )
descendantOptionals = node.optionalTrees and \
[o for o in node.optionalTrees if list(Query._fetchBoundLeaves(o))]
if not descendantOptionals:
top = node
else:
if prolog.DEBUG:
print "descendant optionals: ", descendantOptionals
top = None
child = None
if not node.clash and not descendantOptionals:
#It has compatible bindings and either no optional expansions
#or no *valid* optional expansions
child = Query._SPARQLNode(top,
exprBindings,
expression.patterns,
tS,
expr=node.expr)
child.expand(expression.constraints)
if prolog.DEBUG:
print "Has compatible bindings and no valid optional expansions"
print "Newly bound descendants: "
for c in Query._fetchBoundLeaves(child):
print "\t",c, c.bound
print c.bindings
else:
assert isinstance(expression,Query.Query)
if not expression.top:
#already evaluated a UNION - fetch UNION branches
child = list(fetchUnionBranchesRoots(expression))
else:
#Already been evaluated (non UNION), just attach the SPARQLNode
child = expression.top
if isinstance(child,Query._SPARQLNode):
if node.clash == False and child is not None:
node.children.append(child)
if prolog.DEBUG:
print "Adding %s to %s (a UNION branch)"%(child,node)
else:
assert isinstance(child,list)
for newChild in child:
# if not newChild.clash:
node.children.append(newChild)
if prolog.DEBUG:
print "Adding %s to %s"%(child,node)
if prolog.DEBUG:
print_tree(node)
print "-------------------"
for optTree in node.optionalTrees:
#Join the optional paths as well - those that are bound and valid
for validLeaf in Query._fetchBoundLeaves(optTree):
_ExpandJoin(validLeaf,
expression,
tripleStore,
prolog,
optionalTree=True)
class Join(AlgebraExpression):
"""
[[(P1 AND P2)]](D,G) = [[P1]](D,G) compat [[P2]](D,G)
Join(Ω1, Ω2) = { merge(μ1, μ2) | μ1 in Ω1 and μ2 in Ω2, and μ1 and μ2 are \
compatible }
Pseudocode implementation:
Evaluate BGP1
Traverse to leaves (expand and expandOption leaves) of BGP1, set 'rest' to
triple patterns in BGP2 (filling out bindings).
Trigger another round of expand / expandOptions (from the leaves)
"""
def __init__(self,BGP1,BGP2):
self.left = BGP1
self.right = BGP2
def evaluate(self,tripleStore,initialBindings,prolog):
if prolog.DEBUG:
print "eval(%s,%s,%s)"%(self,initialBindings,tripleStore.graph)
if isinstance(self.left,AlgebraExpression):
left = self.left.evaluate(tripleStore,initialBindings,prolog)
else:
left = self.left
if isinstance(left,BasicGraphPattern):
retval = None
bindings = Query._createInitialBindings(left)
if initialBindings:
bindings.update(initialBindings)
if hasattr(left,'tripleStore'):
#Use the prepared tripleStore
lTS = left.tripleStore
else:
lTS = tripleStore
top = Query._SPARQLNode(None,
bindings,
left.patterns,
lTS,
expr=left)
top.expand(left.constraints)
_ExpandJoin(top,self.right,tripleStore,prolog)
return Query.Query(top, tripleStore)
else:
assert isinstance(left,Query.Query), repr(left)
if left.parent1 and left.parent2:
#union branch. We need to unroll all operands (recursively)
for union_root in fetchUnionBranchesRoots(left):
_ExpandJoin(union_root,self.right,tripleStore,prolog)
else:
for b in Query._fetchBoundLeaves(left.top):
_ExpandJoin(b,self.right,tripleStore,prolog)
return left
def _ExpandLeftJoin(node,expression,tripleStore,prolog,optionalTree=False):
"""
Traverses to the leaves of expansion trees to implement the LeftJoin
operator
"""
currExpr = expression
if prolog.DEBUG:
print "DFS and LeftJoin expansion of "
print_tree(node)
print "---------------------"
print node.bindings
for node in walktree(node,optProxies=True):
if node.clash:
continue
assert len(node.children) == 0
# this is a leaf in the original expansion
if prolog.DEBUG:
print "Performing LeftJoin(%s,..)"%node
if isinstance(currExpr,AlgebraExpression):
#If a Graph pattern evaluate it passing on the leaf bindings
#(possibly as solutions to graph names
if prolog.DEBUG:
print "evaluating B in LeftJoin(A,B)"
print "passing on bindings to %s\n:%s"%(currExpr,
node.bindings.copy())
expression = currExpr.evaluate(tripleStore,node.bindings.copy(),
prolog)
else:
expression = currExpr
if isinstance(expression,BasicGraphPattern):
rightBindings = Query._createInitialBindings(expression)
rightBindings.update(node.bindings)
optTree = Query._SPARQLNode(None,
rightBindings,
expression.patterns,
tripleStore,
expr=expression)
if prolog.DEBUG:
print "evaluating B in LeftJoin(A,B) - a BGP: ", expression
print "Passing on bindings ",rightBindings
optTree.expand(expression.constraints)
for proxy in Query._fetchBoundLeaves(optTree):
#Mark a successful evaluation of LeftJoin (new bindings were added)
#these become proxies for later expressions
proxy.priorLeftJoin=True
else:
if prolog.DEBUG:
print "Attaching previously evaluated node: ", expression.top
assert isinstance(expression,Query.Query)
if not expression.top:
#already evaluated a UNION - fetch UNION branches
optTree = list(fetchUnionBranchesRoots(expression))
else:
#Already been evaluated (non UNION), just attach the SPARQLNode
optTree = expression.top
if prolog.DEBUG:
print "Optional tree: ", optTree
if isinstance(optTree,Query._SPARQLNode):
if optTree.clash == False and optTree is not None:
node.optionalTrees.append(optTree)
if prolog.DEBUG:
print "Adding %s to %s (a UNION branch)"%(optTree,
node.optionalTrees)
else:
assert isinstance(optTree,list)
for newChild in optTree:
# if not newChild.clash:
node.optionalTrees.append(newChild)
if prolog.DEBUG:
print "Adding %s to %s"%(newChild,node.optionalTrees)
if prolog.DEBUG:
print "DFS after LeftJoin expansion "
print_tree(node)
print "---------------------"
class LeftJoin(AlgebraExpression):
"""
Let Ω1 and Ω2 be multisets of solution mappings and F a filter. We define:
LeftJoin(Ω1, Ω2, expr) =
Filter(expr, Join(Ω1, Ω2)) set-union Diff(Ω1, Ω2, expr)
LeftJoin(Ω1, Ω2, expr) =
{ merge(μ1, μ2) | μ1 in Ω1 and μ2 in Ω2, and
μ1 and μ2 are compatible, and
expr(merge(μ1, μ2)) is true }
set-union
{ μ1 | μ1 in Ω1 and μ2 in Ω2, and
μ1 and μ2 are not compatible }
set-union
{ μ1 | μ1 in Ω1and μ2 in Ω2, and μ1 and μ2 are compatible and
expr(merge(μ1, μ2)) is false }
"""
def __init__(self,BGP1,BGP2,expr=None):
self.left = BGP1
self.right = BGP2
def evaluate(self,tripleStore,initialBindings,prolog):
if prolog.DEBUG:
print "eval(%s,%s,%s)"%(self,initialBindings,tripleStore.graph)
if isinstance(self.left,AlgebraExpression):
#print "evaluating A in LeftJoin(A,B) - an expression"
left = self.left.evaluate(tripleStore,initialBindings,prolog)
else:
left = self.left
if isinstance(left,BasicGraphPattern):
#print "expanding A in LeftJoin(A,B) - a BGP: ", left
retval = None
bindings = Query._createInitialBindings(left)
if initialBindings:
bindings.update(initialBindings)
if hasattr(left,'tripleStore'):
#Use the prepared tripleStore
tripleStore = left.tripleStore
top = Query._SPARQLNode(None,
bindings,
left.patterns,
tripleStore,
expr=left)
top.expand(left.constraints)
for b in Query._fetchBoundLeaves(top):
_ExpandLeftJoin(b,self.right,tripleStore,prolog)
#_ExpandLeftJoin(top,self.right,tripleStore,prolog)
return Query.Query(top, tripleStore)
else:
assert isinstance(left,Query.Query), repr(left)
if left.parent1 and left.parent2:
for union_root in fetchUnionBranchesRoots(left):
_ExpandLeftJoin(union_root,self.right,tripleStore,prolog)
else:
for b in Query._fetchBoundLeaves(left.top):
_ExpandLeftJoin(b,self.right,tripleStore,prolog)
#_ExpandLeftJoin(left.top,self.right,tripleStore,prolog)
return left
class Union(AlgebraExpression):
"""
II. [[(P1 UNION P2)]](D,G) = [[P1]](D,G) OR [[P2]](D,G)
Union(Ω1, Ω2) = { μ | μ in Ω1 or μ in Ω2 }
"""
def __init__(self,BGP1,BGP2):
self.left = BGP1
self.right = BGP2
def evaluate(self,tripleStore,initialBindings,prolog):
if prolog.DEBUG:
print "eval(%s,%s,%s)"%(self,initialBindings,tripleStore.graph)
if isinstance(self.left,AlgebraExpression):
left = self.left.evaluate(tripleStore,initialBindings,prolog)
else:
left = self.left
if isinstance(left,BasicGraphPattern):
#The left expression has not been evaluated
retval = None
bindings = Query._createInitialBindings(left)
if initialBindings:
bindings.update(initialBindings)
top = Query._SPARQLNode(None,
bindings,
left.patterns,
tripleStore,
expr=left)
top.expand(left.constraints)
top = Query.Query(top, tripleStore)
else:
#The left expression has already been evaluated
assert isinstance(left,Query.Query), repr(left)
top = left
#Now we evaluate the right expression (independently)
if isinstance(self.right,AlgebraExpression):
#If it is a GraphExpression, 'reduce' it
right = self.right.evaluate(tripleStore,initialBindings,prolog)
else:
right = self.right
tS = tripleStore
if isinstance(right,BasicGraphPattern):
if hasattr(right,'tripleStore'):
tS = right.tripleStore
rightBindings = Query._createInitialBindings(right)
if initialBindings:
rightBindings.update(initialBindings)
rightNode = Query._SPARQLNode(None,
rightBindings,
right.patterns,
tS,
expr=right)
rightNode.expand(right.constraints)
else:
assert isinstance(right,Query.Query), repr(right)
rightNode = right.top
# if prolog.DEBUG:
# print "### Two UNION trees ###"
# print self.left
# print_tree(top.top)
# print self.right
# print_tree(rightNode)
# print "#######################"
#The UNION semantics are implemented by the overidden __add__ method
return top + Query.Query(rightNode, tS)
class GraphExpression(AlgebraExpression):
"""
[24] GraphGraphPattern ::= 'GRAPH' VarOrIRIref GroupGraphPattern
eval(D(G), Graph(IRI,P)) = eval(D(D[i]), P)
eval(D(G), Graph(var,P)) =
multiset-union over IRI i in D : Join( eval(D(D[i]), P) , Omega(?v->i) )
"""
def __init__(self,iriOrVar,GGP):
self.iriOrVar = iriOrVar
self.GGP = GGP
def __repr__(self):
return "Graph(%s,%s)"%(self.iriOrVar,self.GGP)
def evaluate(self,tripleStore,initialBindings,prolog):
"""
.. The GRAPH keyword is used to make the active graph one of all of the
named graphs in the dataset for part of the query ...
"""
if prolog.DEBUG:
print "eval(%s,%s,%s)"%(self,initialBindings,tripleStore.graph)
if isinstance(self.iriOrVar,Variable):
#A variable:
if self.iriOrVar in initialBindings:
#assert initialBindings[self.iriOrVar], "Empty binding for GRAPH variable!"
if prolog.DEBUG:
print "Passing on unified graph name: ",
initialBindings[self.iriOrVar]
tripleStore = sparqlGraph.SPARQLGraph(
Graph(tripleStore.store,
initialBindings[self.iriOrVar])
,dSCompliance=DAWG_DATASET_COMPLIANCE)
else:
if prolog.DEBUG:
print "Setting up BGP to return additional bindings for %s"%self.iriOrVar
tripleStore = sparqlGraph.SPARQLGraph(tripleStore.graph,
graphVariable = self.iriOrVar,
dSCompliance=DAWG_DATASET_COMPLIANCE)
else:
graphName = self.iriOrVar
graphName = convertTerm(graphName,prolog)
if isinstance(tripleStore.graph,ReadOnlyGraphAggregate):
targetGraph = [g for g in tripleStore.graph.graphs
if g.identifier == graphName]
#assert len(targetGraph) == 1
targetGraph = targetGraph[0]
else:
targetGraph = Graph(tripleStore.store,graphName)
tripleStore = sparqlGraph.SPARQLGraph(targetGraph,
dSCompliance=\
DAWG_DATASET_COMPLIANCE)
if isinstance(self.GGP,AlgebraExpression):
#Dont evaluate
return self.GGP.evaluate(tripleStore,initialBindings,prolog)
else:
assert isinstance(self.GGP,BasicGraphPattern),repr(self.GGP)
#Attach the prepared triple store to the BGP
self.GGP.tripleStore = tripleStore
return self.GGP
#########################################
# Tests #
#########################################
TEST1="BASE <http://example.com/> SELECT * WHERE { ?s :p1 ?v1 ; :p2 ?v2 }"
#BGP( ?s :p1 ?v1 .?s :p2 ?v2 )
TEST1_REPR=\
"BGP((?s,http://example.com/p1,?v1),(?s,http://example.com/p2,?v2))"
TEST2 = "BASE <http://example.com/> SELECT * WHERE { { ?s :p1 ?v1 } UNION {?s :p2 ?v2 } }"
#Union( BGP(?s :p1 ?v1) , BGP(?s :p2 ?v2) )
TEST2_REPR=\
"Union(BGP((?s,http://example.com/p1,?v1)),BGP((?s,http://example.com/p2,?v2)))"
TEST3 = "BASE <http://example.com/> SELECT * WHERE { ?s :p1 ?v1 OPTIONAL {?s :p2 ?v2 } }"
#LeftJoin(BGP(?s :p1 ?v1), BGP(?s :p2 ?v2), true)
TEST3_REPR=\
"LeftJoin(BGP((?s,http://example.com/p1,?v1)),BGP((?s,http://example.com/p2,?v2)))"
TEST4 = "BASE <http://example.com/> SELECT * WHERE { ?s :p ?o. { ?s :p1 ?v1 } UNION {?s :p2 ?v2 } }"
#Join(BGP(?s :p ?v),Union(BGP(?s :p1 ?v1), BGP(?s :p2 ?v2)))
TEST4_REPR=\
"Join(BGP((?s,http://example.com/p,?o)),Union(BGP((?s,http://example.com/p1,?v1)),BGP((?s,http://example.com/p2,?v2))))"
TEST5 = "BASE <http://example.com/> SELECT * WHERE { ?a ?b ?c OPTIONAL { ?s :p1 ?v1 } }"
#Join(BGP(?s :p ?v),Union(BGP(?s :p1 ?v1), BGP(?s :p2 ?v2)))
TEST5_REPR=\
"LeftJoin(BGP((?a,?b,?c)),BGP((?s,http://example.com/p1,?v1)))"
TEST6="BASE <http://example.com/> SELECT * WHERE { ?a :b :c OPTIONAL {:x :y :z} { :x1 :y1 :z1 } UNION { :x2 :y2 :z2 } }"
TEST6_REPR=\
"Join(LeftJoin(BGP((?a,http://example.com/b,http://example.com/c)),BGP((http://example.com/x,http://example.com/y,http://example.com/z))),Union(BGP((http://example.com/x1,http://example.com/y1,http://example.com/z1)),BGP((http://example.com/x2,http://example.com/y2,http://example.com/z2))))"
TEST7="BASE <http://example.com/> SELECT * WHERE { ?s :p1 ?v1 OPTIONAL { ?s :p2 ?v2. FILTER( ?v1 < 3 ) } }"
TEST7_REPR=\
"LeftJoin(BGP((?s,http://example.com/p1,?v1)),Filter(.. a filter ..,BGP(?s,http://example.com/p2,?v2)))"
TEST8="BASE <http://example.com/> SELECT * WHERE { ?s :p1 ?v1. FILTER ( ?v1 < 3 ) OPTIONAL { ?s :p3 ?v3 } }"
TEST8_REPR=\
"LeftJoin(Filter(.. a filter ..,BGP(?s,http://example.com/p1,?v1)),BGP((?s,http://example.com/p3,?v3)))"
TEST10=\
"""
PREFIX data: <http://example.org/foaf/>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
SELECT ?mbox ?nick ?ppd
FROM NAMED <http://example.org/foaf/aliceFoaf>
FROM NAMED <http://example.org/foaf/bobFoaf>
WHERE
{
GRAPH data:aliceFoaf
{
?alice foaf:mbox <mailto:alice@work.example> ;
foaf:knows ?whom .
?whom foaf:mbox ?mbox ;
rdfs:seeAlso ?ppd .
?ppd a foaf:PersonalProfileDocument .
} .
GRAPH ?ppd
{
?w foaf:mbox ?mbox ;
foaf:nick ?nick
}
}"""
reducableSPARQL=\
"""
PREFIX mf: <http://www.w3.org/2001/sw/DataAccess/tests/test-manifest#>
PREFIX qt: <http://www.w3.org/2001/sw/DataAccess/tests/test-query#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
SELECT ?test ?testName ?testComment ?query ?result ?testAction
WHERE {
{ ?test a mf:QueryEvaluationTest }
UNION
{ ?test a <http://jena.hpl.hp.com/2005/05/test-manifest-extra#TestQuery> }
?test mf:name ?testName.
OPTIONAL { ?test rdfs:comment ?testComment }
?test mf:action ?testAction;
mf:result ?result.
?testAction qt:query ?query }"""
reducableSPARQLExpr=\
"Join(LeftJoin(Join(Union(BGP((?test,http://www.w3.org/1999/02/22-rdf-syntax-ns#type,mf:QueryEvaluationTest)),BGP((?test,http://www.w3.org/1999/02/22-rdf-syntax-ns#type,http://jena.hpl.hp.com/2005/05/test-manifest-extra#TestQuery))),BGP((?test,mf:name,?testName))),BGP((?test,rdfs:comment,?testComment))),BGP((?test,mf:action,?testAction),(?test,mf:result,?result),(?testAction,qt:query,?query)))"
ExprTests = \
[
(TEST1,TEST1_REPR),
(TEST2,TEST2_REPR),
(TEST3,TEST3_REPR),
(TEST4,TEST4_REPR),
(TEST5,TEST5_REPR),
(TEST6,TEST6_REPR),
(TEST7,TEST7_REPR),
(TEST8,TEST8_REPR),
(reducableSPARQL,reducableSPARQLExpr),
]
test_graph_a = """
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
_:a foaf:name "Alice" .
_:a foaf:mbox <mailto:alice@work.example> .
_:a foaf:knows _:b .
_:b foaf:name "Bob" .
_:b foaf:mbox <mailto:bob@work.example> .
_:b foaf:nick "Bobby" .
_:b rdfs:seeAlso <http://example.org/foaf/bobFoaf> .
<http://example.org/foaf/bobFoaf>
rdf:type foaf:PersonalProfileDocument ."""
test_graph_b = """
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
_:z foaf:mbox <mailto:bob@work.example> .
_:z rdfs:seeAlso <http://example.org/foaf/bobFoaf> .
_:z foaf:nick "Robert" .
<http://example.org/foaf/bobFoaf>
rdf:type foaf:PersonalProfileDocument ."""
scopingQuery=\
"""
PREFIX data: <http://example.org/foaf/>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
SELECT ?ppd
FROM NAMED <http://example.org/foaf/aliceFoaf>
FROM NAMED <http://example.org/foaf/bobFoaf>
WHERE
{
GRAPH ?ppd { ?b foaf:name "Bob" . } .
GRAPH ?ppd { ?doc a foaf:PersonalProfileDocument . }
}"""
class TestSPARQLAlgebra(unittest.TestCase):
def setUp(self):
self.store = plugin.get('IOMemory', Store)()
self.graph1 = Graph(self.store,identifier=URIRef('http://example.org/foaf/aliceFoaf'))
self.graph1.parse(StringIO(test_graph_a), format="n3")
self.graph2 = Graph(self.store,identifier=URIRef('http://example.org/foaf/bobFoaf'))
self.graph2.parse(StringIO(test_graph_b), format="n3")
self.unionGraph = ReadOnlyGraphAggregate(graphs=[self.graph1,self.graph2],store=self.store)
# def testScoping(self):
# from rdflib.sparql.bison.Processor import Parse
# from rdflib.sparql.QueryResult import SPARQLQueryResult
# from rdflib.sparql.bison.Query import Prolog
# p = Parse(scopingQuery)
# prolog = p.prolog
# if prolog is None:
# prolog = Prolog(u'',[])
# prolog.DEBUG = True
# rt = TopEvaluate(p,self.unionGraph,passedBindings = {},DEBUG=False)
# rt = SPARQLQueryResult(rt).serialize(format='python')
# self.failUnless(len(rt) == 1,"Expected 1 item solution set")
# for ppd in rt:
# self.failUnless(ppd == URIRef('http://example.org/foaf/aliceFoaf'),
# "Unexpected ?mbox binding :\n %s" % ppd)
def testExpressions(self):
from rdflib.sparql.bison.Processor import Parse
global prolog
for inExpr,outExpr in ExprTests:
p = Parse(inExpr)
prolog = p.prolog
p = p.query.whereClause.parsedGraphPattern.graphPatterns
if prolog is None:
from rdflib.sparql.bison.Query import Prolog
prolog = Prolog(u'',[])
if not hasattr(prolog,'DEBUG'):
prolog.DEBUG = False
self.assertEquals(repr(reduce(ReduceToAlgebra,p,None)),outExpr)
def testSimpleGraphPattern(self):
from rdflib.sparql.bison.Processor import Parse
global prolog
p = Parse("BASE <http://example.com/> SELECT ?ptrec WHERE { GRAPH ?ptrec { ?data :foo 'bar'. } }")
prolog = p.prolog
p = p.query.whereClause.parsedGraphPattern.graphPatterns
if prolog is None:
from rdflib.sparql.bison.Query import Prolog
prolog = Prolog(u'',[])
prolog.DEBUG = True
assert isinstance(reduce(ReduceToAlgebra,p,None),GraphExpression)
# def testGraphEvaluation(self):
# from rdflib.sparql.bison.Processor import Parse
# p = Parse(TEST10)
# print TEST10
# rt = TopEvaluate(p,self.unionGraph,passedBindings = {})
# from rdflib.sparql.QueryResult import SPARQLQueryResult
# rt = SPARQLQueryResult(rt).serialize(format='python')
# self.failUnless(len(rt) == 1,"Expected 1 item solution set")
# for mbox,nick,ppd in rt:
# self.failUnless(mbox == URIRef('mailto:bob@work.example'),
# "Unexpected ?mbox binding :\n %s" % mbox)
# self.failUnless(nick == Literal("Robert"),
# "Unexpected ?nick binding :\n %s" % nick)
# self.failUnless(ppd == URIRef('http://example.org/foaf/bobFoaf'),
# "Unexpected ?ppd binding :\n %s" % ppd)
if __name__ == '__main__':
unittest.main()
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