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/*
* Copyright 2020, 2021 KRR Oxford
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package uk.ac.ox.cs.rsacomb.sparql
import java.util.{Map => JMap, HashMap => JHashMap}
import tech.oxfordsemantic.jrdfox.Prefixes
import tech.oxfordsemantic.jrdfox.client.DataStoreConnection
import tech.oxfordsemantic.jrdfox.logic.datalog.{TupleTableAtom, TupleTableName}
import tech.oxfordsemantic.jrdfox.logic.expression.Variable
import tech.oxfordsemantic.jrdfox.logic.sparql.pattern.{
ConjunctionPattern,
QueryPattern,
TriplePattern
}
import tech.oxfordsemantic.jrdfox.logic.sparql.statement.SelectQuery
import uk.ac.ox.cs.rsacomb.util.RDFoxUtil
/** Factory for [[uk.ac.ox.cs.rsacomb.sparql.ConjunctiveQuery]]. */
object ConjunctiveQuery {
/** Creates a new ConjunctiveQuery instance.
*
* @param query `SelectQuery` instance representing the actual query
*/
def apply(id: Int, query: SelectQuery): ConjunctiveQuery =
new ConjunctiveQuery(id, query)
/** Creates a new ConjunctiveQuery from a query string
*
* @param query a string representing the query in SPARQL format
* @param prefixes additional prefixes used in the query. Defaults to
* an empty set of prefixes.
* @return an [[scala.Option]] containing a ConjunctiveQuery if the
* input query represents one, None is returned otherwise.
*/
def parse(
id: Int,
query: String,
prefixes: Prefixes = new Prefixes()
): Option[ConjunctiveQuery] =
RDFoxUtil.parseSelectQuery(query, prefixes).map(ConjunctiveQuery(id, _))
}
/** A conjunctive query
*
* A thin layer around
* [[tech.oxfordsemantics.jrdfox.logic.sparql.statement.SelectQuery]].
*
* Instances should be created using the companion object.
*
* @todo additional checks need to be performed in order for a
* `SelectQuery` to be considered a conjunctive query.
*/
class ConjunctiveQuery(
val id: Int,
query: SelectQuery,
val prefixes: Prefixes = new Prefixes()
) {
/** Simplify conversion between Java and Scala collections */
import uk.ac.ox.cs.rsacomb.implicits.JavaCollections._
/** SELECT section of the SPARQL query.
*
* Simply exposes the underlying `getSelection` method in
* [[tech.oxfordsemantics.jrdfox.logic.sparql.statement.SelectQuery]].
*/
val select = query.getSelection
/** WHERE section of the SPARQL query.
*
* Simply exposes the underlying `getWherePattern` method in
* [[tech.oxfordsemantics.jrdfox.logic.sparql.statement.QueryBody]].
*/
val where = query.getQueryBody.getWherePattern
/** Returns true if it is a boolean CQ.
*
* @note checking for `select` being empty is not enough. When a
* query selects '''all''' variables with `*`, `select` is empty as
* well.
*/
val bcq: Boolean = select.isEmpty && !query.getAllPossibleVariables
/** Returns the query body as a sequence of atoms (triples). */
def atoms(graph: TupleTableName): List[TupleTableAtom] =
where
.asInstanceOf[ConjunctionPattern]
.getConjuncts
.collect { case t: TriplePattern =>
TupleTableAtom.create(graph, t.getSubject, t.getPredicate, t.getObject)
}
// where match {
// case b: ConjunctionPattern => {
// b.getConjuncts.toList.flatMap { conj: QueryPattern =>
// conj match {
// case c: TriplePattern =>
// Seq(
// TupleTableAtom.rdf(c.getSubject, c.getPredicate, c.getObject)
// )
// case _ => List()
// }
// }
// }
// case _ => List()
// }
/** Returns the full collection of variables involved in the query. */
val variables: List[Variable] =
where
.asInstanceOf[ConjunctionPattern]
.getConjuncts
.collect { case t: TriplePattern =>
Set(t.getSubject, t.getPredicate, t.getObject).collect {
case v: Variable => v
}
}
.flatten
.distinct
// (where match {
// case b: ConjunctionPattern => {
// b.getConjuncts.toList.flatMap { conj: QueryPattern =>
// conj match {
// case c: TriplePattern =>
// Set(c.getSubject, c.getPredicate, c.getObject).collect {
// case v: Variable => v
// }
// case _ => List()
// }
// }
// }
// case _ => List()
// }).distinct
/** Returns the collection of answer variables in the query. */
val answer: List[Variable] =
if (query.getAllPossibleVariables)
variables
else
select.map(_.getVariable).toList.distinct
/** Returns the collection of bounded (existential) variables in the query. */
val bounded: List[Variable] = variables diff answer
override def toString(): String = query.toString
}
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