public override void SetObjectOperator(ResultOperatorBase resultOperator) { base.SetObjectOperator(resultOperator); if (ObjectVariable != null) { if (resultOperator is AnyResultOperator) { // When using x.Any(), we add a LIMIT 1 the query results in the SparqlQueryGenerator. // When using .Any(x => ..), the variable x is locally scoped and cannot be // used in outer queries. Therefore do not need to actually select it. // This avoids issues with Stardog: // https://community.stardog.com/t/sparql-union-only-working-with-inferencing-enabled/1040/9 } else if (resultOperator is AverageResultOperator) { var aggregate = new AverageAggregate(new VariableTerm(ObjectVariable.Name)); SetObjectVariable(aggregate.AsSparqlVariable(), true); } else if (resultOperator is CountResultOperator) { var aggregate = new CountDistinctAggregate(new VariableTerm(ObjectVariable.Name)); SetObjectVariable(aggregate.AsSparqlVariable(), true); } else if (resultOperator is FirstResultOperator) { // "Using LIMIT and OFFSET to select different subsets of the query solutions // will not be useful unless the order is made predictable by using ORDER BY." // Source: https://www.w3.org/TR/2013/REC-sparql11-query-20130321/#modOffset // Therefore, if no ordering exists we add an ordering on the current subject // to make the query result predictable. if (!QueryModel.BodyClauses.OfType <OrderByClause>().Any()) { OrderBy(SubjectVariable); } else { // In case the order was make explicit, we have to do nothing. } Limit(1); } else if (resultOperator is LastResultOperator) { // "Using LIMIT and OFFSET to select different subsets of the query solutions // will not be useful unless the order is made predictable by using ORDER BY." // Source: https://www.w3.org/TR/2013/REC-sparql11-query-20130321/#modOffset // Therefore, if no ordering exists we add an ordering on the current subject // to make the query result predictable. if (!QueryModel.BodyClauses.OfType <OrderByClause>().Any()) { OrderByDescending(SubjectVariable); } else { // Inverting the direction of the first ordering is handled in SparqlQueryModelVisitor.VisitOrdering(). // This is because the orderings are not necessarily processed *before* the result operators.. } Limit(1); } else if (resultOperator is MaxResultOperator) { var aggregate = new MaxAggregate(new VariableTerm(ObjectVariable.Name)); SetObjectVariable(aggregate.AsSparqlVariable(), true); } else if (resultOperator is MinResultOperator) { var aggregate = new MinAggregate(new VariableTerm(ObjectVariable.Name)); SetObjectVariable(aggregate.AsSparqlVariable(), true); } else if (resultOperator is SumResultOperator) { var aggregate = new SumAggregate(new VariableTerm(ObjectVariable.Name)); SetObjectVariable(aggregate.AsSparqlVariable(), true); } else if (resultOperator is OfTypeResultOperator) { OfTypeResultOperator ofType = resultOperator as OfTypeResultOperator; RdfClassAttribute type = ofType.SearchedItemType.TryGetCustomAttribute <RdfClassAttribute>(); if (type == null) { throw new ArgumentException("No RdfClass attrribute declared on type: " + ofType.SearchedItemType); } SparqlVariable s = ObjectVariable; SparqlVariable p = VariableGenerator.CreatePredicateVariable(); SparqlVariable o = VariableGenerator.CreateObjectVariable(); WhereResource(s, p, o); WhereResourceOfType(o, ofType.SearchedItemType); } else if (resultOperator is SkipResultOperator) { SkipResultOperator op = resultOperator as SkipResultOperator; Offset(int.Parse(op.Count.ToString())); } else if (resultOperator is TakeResultOperator) { TakeResultOperator op = resultOperator as TakeResultOperator; Limit(int.Parse(op.Count.ToString())); } else { throw new NotImplementedException(resultOperator.ToString()); } } }
private SparqlVariable BuildMemberAccess(MemberExpression memberExpression, IGraphPatternBuilder patternBuilder) { MemberInfo member = memberExpression.Member; // If we do access a member of a system type, like string.Length we actually select the // the declaring member and invoke a SPARQL built in call to get the value. if (member.IsBuiltInCall()) { MemberExpression parentMember = memberExpression.Expression as MemberExpression; return(BuildMemberAccess(parentMember, patternBuilder)); } else if (memberExpression.Expression is MemberExpression) { MemberExpression parentMember = memberExpression.Expression as MemberExpression; // Note: When we build an optional property path, we consider the relation to the // parent properties of the accessed property to be non-optional. IGraphPatternBuilder builder = member.IsUriType() ? patternBuilder : PatternBuilder; // We might encounter property paths (i.e. contact.Organization.Name). Therefore, // implement the parent expression of the current member recursively.. SparqlVariable po = BuildMemberAccess(parentMember, builder); // If we are building a node on a property path (parentExpression != null), we associate // the object variable with the parent expression so that it becomes the subject of the parent. VariableGenerator.SetSubjectVariable(memberExpression, po); } if (member.IsUriType()) { // When we access the .Uri member of a resource we do not need a property mapping and return the subject as the bound variable. // We create a triple pattern describing the resource in the local scope just in case it has not been described yet. // Todo: Improve. Check if triples actually need to be asserted. SparqlVariable s = VariableGenerator.TryGetSubjectVariable(memberExpression) ?? SubjectVariable; SparqlVariable p = VariableGenerator.CreatePredicateVariable(); SparqlVariable o = VariableGenerator.CreateObjectVariable(memberExpression); patternBuilder.Where(t => t.Subject(s).Predicate(p).Object(o)); VariableGenerator.SetSubjectVariable(memberExpression, s); return(s); } else if (memberExpression.Expression is QuerySourceReferenceExpression) { QuerySourceReferenceExpression querySource = memberExpression.Expression as QuerySourceReferenceExpression; if (VariableGenerator.TryGetSubjectVariable(memberExpression) == VariableGenerator.GlobalSubject) { // In case the accessed member is the global query subject (i.e. from x select x.Y).. SparqlVariable s = VariableGenerator.TryGetSubjectVariable(querySource); SparqlVariable o = VariableGenerator.GlobalSubject; if (s == null) { s = VariableGenerator.CreateSubjectVariable(querySource); BuildMemberAccess(memberExpression, patternBuilder, member, s, o); } return(o); } else { // Otherwise we are accessing a member of the globale query subject (i.e. from x where x.Y select x) SparqlVariable s = VariableGenerator.TryGetSubjectVariable(querySource) ?? VariableGenerator.GlobalSubject; SparqlVariable o = VariableGenerator.TryGetObjectVariable(memberExpression) ?? VariableGenerator.CreateObjectVariable(memberExpression); BuildMemberAccess(memberExpression, patternBuilder, member, s, o); return(o); } } else { SparqlVariable s = VariableGenerator.TryGetSubjectVariable(memberExpression) ?? VariableGenerator.CreateSubjectVariable(memberExpression); SparqlVariable o = VariableGenerator.TryGetObjectVariable(memberExpression) ?? VariableGenerator.CreateObjectVariable(memberExpression); BuildMemberAccess(memberExpression, patternBuilder, member, s, o); return(o); } }