2 files changed, 32 insertions, 18 deletions

diff --git a/src/main/scala/uk/ac/ox/cs/rsacomb/sparql/ConjunctiveQueryAnswers.scala b/src/main/scala/uk/ac/ox/cs/rsacomb/sparql/ConjunctiveQueryAnswers.scala
index ded8d6b..0f830eb 100644
--- a/src/main/scala/uk/ac/ox/cs/rsacomb/sparql/ConjunctiveQueryAnswers.scala
+++ b/src/main/scala/uk/ac/ox/cs/rsacomb/sparql/ConjunctiveQueryAnswers.scala
@@ -1,6 +1,6 @@
 package uk.ac.ox.cs.rsacomb.sparql
 
-import tech.oxfordsemantic.jrdfox.logic.expression.Resource
+import tech.oxfordsemantic.jrdfox.logic.expression.{Resource, Variable}
 
 /** A collections of answers to a query.
   *
@@ -13,6 +13,7 @@ import tech.oxfordsemantic.jrdfox.logic.expression.Resource
   */
 class ConjunctiveQueryAnswers(
     bcq: Boolean,
+    val variables: Seq[Variable],
     val answers: Seq[Seq[Resource]]
 ) {
 
@@ -21,8 +22,11 @@ class ConjunctiveQueryAnswers(
       if (answers.isEmpty) "FALSE" else "TRUE"
     } else {
       if (answers.isEmpty)
-        "NO ANSWER"
-      else
-        answers.map(_.mkString("(", ", ", ")")).mkString("\n")
+        "NO ANSWER."
+      else {
+        val header = variables map (_.getName) mkString "\t"
+        val body = answers.map(_.mkString("\t")).mkString("\n")
+        s"$header\n$body"
+      }
     }
 }
diff --git a/src/test/scala/uk/ac/ox/cs/rsacomb/sparql/ConjunctiveQueryAnswerSpecs.scala b/src/test/scala/uk/ac/ox/cs/rsacomb/sparql/ConjunctiveQueryAnswerSpecs.scala
index 65c3e29..ddc6377 100644
--- a/src/test/scala/uk/ac/ox/cs/rsacomb/sparql/ConjunctiveQueryAnswerSpecs.scala
+++ b/src/test/scala/uk/ac/ox/cs/rsacomb/sparql/ConjunctiveQueryAnswerSpecs.scala
@@ -2,28 +2,38 @@ package uk.ac.ox.cs.rsacomb.sparql
 
 import org.scalatest.flatspec.AnyFlatSpec
 import org.scalatest.matchers.should.Matchers
-import tech.oxfordsemantic.jrdfox.logic.expression.IRI
+import tech.oxfordsemantic.jrdfox.logic.expression.{IRI, Variable}
 
 object ConjunctiveQueryAnswerSpec {
 
+  val varX = Variable.create("X")
+  val varY = Variable.create("Y")
+  val varZ = Variable.create("Z")
   val iri1 = IRI.create("_:iri1")
   val iri2 = IRI.create("_:iri2")
   val iri3 = IRI.create("_:iri3")
 
-  val oneAnswer = new ConjunctiveQueryAnswers(false, Seq(Seq(iri1, iri2, iri3)))
+  val oneAnswer = new ConjunctiveQueryAnswers(
+    false,
+    Seq(varX, varY, varZ),
+    Seq(Seq(iri1, iri2, iri3))
+  )
   val multipleAnswers =
     new ConjunctiveQueryAnswers(
       false,
+      Seq(varY, varZ),
       Seq(Seq(iri1, iri1), Seq(iri1, iri2), Seq(iri1, iri3))
     )
-  val noAnswer = new ConjunctiveQueryAnswers(false, Seq())
-  val emptyAnswer = new ConjunctiveQueryAnswers(false, Seq(Seq()))
+  val noAnswer = new ConjunctiveQueryAnswers(false, Seq(), Seq())
+  val emptyAnswer =
+    new ConjunctiveQueryAnswers(false, Seq(varX, varY), Seq(Seq()))
 
-  val falseAnswer = new ConjunctiveQueryAnswers(true, Seq())
-  val trueAnswer1 = new ConjunctiveQueryAnswers(true, Seq(Seq()))
+  val falseAnswer = new ConjunctiveQueryAnswers(true, Seq(), Seq())
+  val trueAnswer1 = new ConjunctiveQueryAnswers(true, Seq(), Seq(Seq()))
   val trueAnswer2 =
     new ConjunctiveQueryAnswers(
       true,
+      Seq(varX, varY),
       Seq(Seq(iri1, iri1), Seq(iri1, iri2), Seq(iri1, iri3))
     )
 }
@@ -32,20 +42,20 @@ class ConjunctiveQueryAnswerSpec extends AnyFlatSpec with Matchers {
 
   import ConjunctiveQueryAnswerSpec._
 
-  "A conjunctive query" should "print a single line if it has a single answer" in {
-    oneAnswer.toString shouldBe s"($iri1, $iri2, $iri3)"
+  "A conjunctive query" should "print an header and a single line if it has a single answer" in {
+    oneAnswer.toString shouldBe s"X\tY\tZ\n$iri1\t$iri2\t$iri3"
   }
 
-  it should "print multiple answers on multiple lines" in {
-    multipleAnswers.toString shouldBe s"($iri1, $iri1)\n($iri1, $iri2)\n($iri1, $iri3)"
+  it should "print a header and multiple answers on multiple lines" in {
+    multipleAnswers.toString shouldBe s"Y\tZ\n$iri1\t$iri1\n$iri1\t$iri2\n$iri1\t$iri3"
   }
 
-  it should "print a special \"NO ANSWER\" string when it has no answer" in {
-    noAnswer.toString shouldBe "NO ANSWER"
+  it should "print a special \"NO ANSWER.\" string when it has no answer" in {
+    noAnswer.toString shouldBe "NO ANSWER."
   }
 
-  it should "print an empty list when it has an empty answer" in {
-    emptyAnswer.toString shouldBe "()"
+  it should "print only the header when it has an empty answer" in {
+    emptyAnswer.toString shouldBe "X\tY\n"
   }
 
   "A boolean conjunctive query" should "print \"FALSE\" when it has no answer" in {