/// <summary>
/// Evaluates a Zero or More Path
/// </summary>
/// <param name="context">Evaluation Context</param>
/// <returns></returns>
public override BaseMultiset Evaluate(SparqlEvaluationContext context)
{
List<List<INode>> paths = new List<List<INode>>();
BaseMultiset initialInput = context.InputMultiset;
int step = 0, prevCount = 0, skipCount = 0;
String subjVar = this.PathStart.VariableName;
String objVar = this.PathEnd.VariableName;
bool bothTerms = (subjVar == null && objVar == null);
bool reverse = false;
if (subjVar == null || (subjVar != null && context.InputMultiset.ContainsVariable(subjVar)) || (objVar != null && !context.InputMultiset.ContainsVariable(objVar)))
{
//Work Forwards from the Starting Term or Bound Variable
//OR if there is no Ending Term or Bound Variable work forwards regardless
if (subjVar == null)
{
paths.Add(((NodeMatchPattern)this.PathStart).Node.AsEnumerable().ToList());
}
else if (context.InputMultiset.ContainsVariable(subjVar))
{
paths.AddRange((from s in context.InputMultiset.Sets
where s[subjVar] != null
select s[subjVar]).Distinct().Select(n => n.AsEnumerable().ToList()));
}
}
else if (objVar == null || (objVar != null && context.InputMultiset.ContainsVariable(objVar)))
{
//Work Backwards from Ending Term or Bound Variable
if (objVar == null)
{
paths.Add(((NodeMatchPattern)this.PathEnd).Node.AsEnumerable().ToList());
}
else
{
paths.AddRange((from s in context.InputMultiset.Sets
where s[objVar] != null
select s[objVar]).Distinct().Select(n => n.AsEnumerable().ToList()));
}
reverse = true;
}
if (paths.Count == 0)
{
this.GetPathStarts(context, paths, reverse);
}
//Traverse the Paths
do
{
prevCount = paths.Count;
foreach (List<INode> path in paths.Skip(skipCount).ToList())
{
foreach (INode nextStep in this.EvaluateStep(context, path, reverse))
{
List<INode> newPath = new List<INode>(path);
newPath.Add(nextStep);
paths.Add(newPath);
}
}
//Update Counts
//skipCount is used to indicate the paths which we will ignore for the purposes of
//trying to further extend since we've already done them once
step++;
if (paths.Count == 0) break;
skipCount = prevCount;
//Can short circuit evaluation here if both are terms and any path is acceptable
if (bothTerms)
{
bool exit = false;
foreach (List<INode> path in paths)
{
if (reverse)
{
if (this.PathEnd.Accepts(context, path[0]) && this.PathStart.Accepts(context, path[path.Count - 1]))
{
exit = true;
break;
}
}
else
{
if (this.PathStart.Accepts(context, path[0]) && this.PathEnd.Accepts(context, path[path.Count - 1]))
{
exit = true;
break;
}
}
}
if (exit) break;
}
} while (paths.Count > prevCount || (step == 1 && paths.Count == prevCount));
if (paths.Count == 0)
{
//If all path starts lead nowhere then we get the Null Multiset as a result
context.OutputMultiset = new NullMultiset();
}
else
{
context.OutputMultiset = new Multiset();
//Evaluate the Paths to check that are acceptable
foreach (List<INode> path in paths)
{
if (reverse)
{
if (this.PathEnd.Accepts(context, path[0]) && this.PathStart.Accepts(context, path[path.Count - 1]))
{
Set s = new Set();
if (!bothTerms)
{
if (subjVar != null) s.Add(subjVar, path[path.Count - 1]);
if (objVar != null) s.Add(objVar, path[0]);
}
context.OutputMultiset.Add(s);
//If both are terms can short circuit evaluation here
//It is sufficient just to determine that there is one path possible
if (bothTerms) break;
}
}
else
{
if (this.PathStart.Accepts(context, path[0]) && this.PathEnd.Accepts(context, path[path.Count - 1]))
{
Set s = new Set();
if (!bothTerms)
{
if (subjVar != null) s.Add(subjVar, path[0]);
if (objVar != null) s.Add(objVar, path[path.Count - 1]);
}
context.OutputMultiset.Add(s);
//If both are terms can short circuit evaluation here
//It is sufficient just to determine that there is one path possible
if (bothTerms) break;
}
}
}
//Now add the zero length paths into
IEnumerable<INode> nodes;
if (subjVar != null)
{
if (objVar != null)
{
nodes = (from s in context.OutputMultiset.Sets
where s[subjVar] != null
select s[subjVar]).Concat(from s in context.OutputMultiset.Sets
where s[objVar] != null
select s[objVar]).Distinct();
}
else
{
nodes = (from s in context.OutputMultiset.Sets
where s[subjVar] != null
select s[subjVar]).Distinct();
}
}
else if (objVar != null)
{
nodes = (from s in context.OutputMultiset.Sets
where s[objVar] != null
select s[objVar]).Distinct();
}
else
{
nodes = Enumerable.Empty<INode>();
}
if (bothTerms)
{
//If both were terms transform to an Identity/Null Multiset as appropriate
if (context.OutputMultiset.IsEmpty)
{
context.OutputMultiset = new NullMultiset();
}
else
{
context.OutputMultiset = new IdentityMultiset();
}
}
//Then union in the zero length paths
ZeroLengthPath zeroPath = new ZeroLengthPath(this.PathStart, this.PathEnd, this.Path);
BaseMultiset currResults = context.OutputMultiset;
context.OutputMultiset = new Multiset();
BaseMultiset results = context.Evaluate(zeroPath);//zeroPath.Evaluate(context);
context.OutputMultiset = currResults;
foreach (Set s in results.Sets)
{
if (!context.OutputMultiset.Sets.Contains(s))
{
context.OutputMultiset.Add(new Set(s));
}
}
}
context.InputMultiset = initialInput;
return context.OutputMultiset;
}
/// <summary>
/// Converts a Path into its Algebra Form
/// </summary>
/// <param name="context">Path Transformation Context</param>
/// <returns></returns>
public override ISparqlAlgebra ToAlgebra(PathTransformContext context)
{
PathTransformContext lhsContext = new PathTransformContext(context);
PathTransformContext rhsContext = new PathTransformContext(context);
ISparqlAlgebra lhs = new ZeroLengthPath(lhsContext.Subject, lhsContext.Object, this._path);
ISparqlAlgebra rhs = this._path.ToAlgebra(context);
return new Union(lhs, rhs);
}
/// <summary>
/// Evaluates a Zero or More Path
/// </summary>
/// <param name="context">Evaluation Context</param>
/// <returns></returns>
public override BaseMultiset Evaluate(SparqlEvaluationContext context)
{
List <List <INode> > paths = new List <List <INode> >();
BaseMultiset initialInput = context.InputMultiset;
int step = 0, prevCount = 0, skipCount = 0;
String subjVar = PathStart.VariableName;
String objVar = PathEnd.VariableName;
bool bothTerms = (subjVar == null && objVar == null);
bool reverse = false;
if (subjVar == null || (context.InputMultiset.ContainsVariable(subjVar)))
{
// Work Forwards from the Starting Term or Bound Variable
// OR if there is no Ending Term or Bound Variable work forwards regardless
if (subjVar == null)
{
paths.Add(((NodeMatchPattern)PathStart).Node.AsEnumerable().ToList());
}
else if (context.InputMultiset.ContainsVariable(subjVar))
{
paths.AddRange((from s in context.InputMultiset.Sets
where s[subjVar] != null
select s[subjVar]).Distinct().Select(n => n.AsEnumerable().ToList()));
}
}
else if (objVar == null || (context.InputMultiset.ContainsVariable(objVar)))
{
// Work Backwards from Ending Term or Bound Variable
if (objVar == null)
{
paths.Add(((NodeMatchPattern)PathEnd).Node.AsEnumerable().ToList());
}
else
{
paths.AddRange((from s in context.InputMultiset.Sets
where s[objVar] != null
select s[objVar]).Distinct().Select(n => n.AsEnumerable().ToList()));
}
reverse = true;
}
if (paths.Count == 0)
{
GetPathStarts(context, paths, reverse);
}
// Traverse the Paths
do
{
prevCount = paths.Count;
foreach (List <INode> path in paths.Skip(skipCount).ToList())
{
foreach (INode nextStep in EvaluateStep(context, path, reverse))
{
List <INode> newPath = new List <INode>(path);
newPath.Add(nextStep);
paths.Add(newPath);
}
}
// Update Counts
// skipCount is used to indicate the paths which we will ignore for the purposes of
// trying to further extend since we've already done them once
step++;
if (paths.Count == 0)
{
break;
}
skipCount = prevCount;
// Can short circuit evaluation here if both are terms and any path is acceptable
if (bothTerms)
{
bool exit = false;
foreach (List <INode> path in paths)
{
if (reverse)
{
if (PathEnd.Accepts(context, path[0]) && PathStart.Accepts(context, path[path.Count - 1]))
{
exit = true;
break;
}
}
else
{
if (PathStart.Accepts(context, path[0]) && PathEnd.Accepts(context, path[path.Count - 1]))
{
exit = true;
break;
}
}
}
if (exit)
{
break;
}
}
} while (paths.Count > prevCount || (step == 1 && paths.Count == prevCount));
if (paths.Count == 0)
{
// If all path starts lead nowhere then we get the Null Multiset as a result
context.OutputMultiset = new NullMultiset();
}
else
{
context.OutputMultiset = new Multiset();
// Evaluate the Paths to check that are acceptable
HashSet <ISet> returnedPaths = new HashSet <ISet>();
foreach (List <INode> path in paths)
{
if (reverse)
{
if (PathEnd.Accepts(context, path[0]) && PathStart.Accepts(context, path[path.Count - 1]))
{
Set s = new Set();
if (!bothTerms)
{
if (subjVar != null)
{
s.Add(subjVar, path[path.Count - 1]);
}
if (objVar != null)
{
s.Add(objVar, path[0]);
}
}
// Make sure to check for uniqueness
if (returnedPaths.Contains(s))
{
continue;
}
context.OutputMultiset.Add(s);
returnedPaths.Add(s);
// If both are terms can short circuit evaluation here
// It is sufficient just to determine that there is one path possible
if (bothTerms)
{
break;
}
}
}
else
{
if (PathStart.Accepts(context, path[0]) && PathEnd.Accepts(context, path[path.Count - 1]))
{
Set s = new Set();
if (!bothTerms)
{
if (subjVar != null)
{
s.Add(subjVar, path[0]);
}
if (objVar != null)
{
s.Add(objVar, path[path.Count - 1]);
}
}
// Make sure to check for uniqueness
if (returnedPaths.Contains(s))
{
continue;
}
context.OutputMultiset.Add(s);
returnedPaths.Add(s);
// If both are terms can short circuit evaluation here
// It is sufficient just to determine that there is one path possible
if (bothTerms)
{
break;
}
}
}
}
// Now add the zero length paths into
IEnumerable <INode> nodes;
if (subjVar != null)
{
if (objVar != null)
{
nodes = (from s in context.OutputMultiset.Sets
where s[subjVar] != null
select s[subjVar]).Concat(from s in context.OutputMultiset.Sets
where s[objVar] != null
select s[objVar]).Distinct();
}
else
{
nodes = (from s in context.OutputMultiset.Sets
where s[subjVar] != null
select s[subjVar]).Distinct();
}
}
else if (objVar != null)
{
nodes = (from s in context.OutputMultiset.Sets
where s[objVar] != null
select s[objVar]).Distinct();
}
else
{
nodes = Enumerable.Empty <INode>();
}
if (bothTerms)
{
// If both were terms transform to an Identity/Null Multiset as appropriate
if (context.OutputMultiset.IsEmpty)
{
context.OutputMultiset = new NullMultiset();
}
else
{
context.OutputMultiset = new IdentityMultiset();
}
}
// Then union in the zero length paths
context.InputMultiset = initialInput;
ZeroLengthPath zeroPath = new ZeroLengthPath(PathStart, PathEnd, Path);
BaseMultiset currResults = context.OutputMultiset;
context.OutputMultiset = new Multiset();
BaseMultiset results = context.Evaluate(zeroPath);//zeroPath.Evaluate(context);
context.OutputMultiset = currResults;
foreach (ISet s in results.Sets)
{
if (!context.OutputMultiset.Sets.Contains(s))
{
context.OutputMultiset.Add(s.Copy());
}
}
}
context.InputMultiset = initialInput;
return(context.OutputMultiset);
}
