IssueBanana.scala

import org.w3.banana.{Sesame,RDF,RDFModule,RDFOpsModule,TurtleWriterModule}
import org.apache.spark.rdd.RDD

// My Code
trait BlazeSesame extends Sesame
trait BlazeSesameModule extends SesameModule {
  type Rdf = BlazeSesame
}

trait MyDependencies extends RDFModule with RDFOpsModule with TurtleWriterModule with Serializable
trait MyImpl extends MyDependencies {
  def mapFn[Rdf <: RDF](r : (Seq[String],(String,String)))):Seq[Rdf#Triple] = {
    val rdfs = RDFSPrefix[Rdf]
    val sf = MyPrefix[Rdf]

    val sub1:Rdf#URI = sf.getABox(x._1.head)
    val sub2:Rdf#URI = sf.getABox(x._1(1))
    Seq(
        Triple(sub2, rdf.typ, sf.MyObject),
        Triple(sub2, rdf.typ, sf.MyObject)
      )
  }
  def main() {
    import ops._
    val r: RDD[(Seq[String],(String,String))] = getRDD()
    val l = r.flatMap(mapFn).collect().toList // this is where I am getting the error "No ClassTag available for Rdf#Triple"
    turtleWriter.asString(Graph(l),base = "")
  }
}

object MyImplObj extends MyImpl with BlazeSesameModule

I fixed it.

Spark's RDD require an implicit ClassTag with most of it's methods like map & flatMap. Since, being an user-defined type RDF#Triple's ClassTag had to be explicitly made available.

• To have the implicit ClassTag available at the parent trait, it is required to be as one of the implicit property

trait MyImpl extends MyDependencies {
    implicit val ctt: ClassTag[Rdf#Triple]

• The actual value will come from one of the implementing types

trait BlazeSesameModule extends SesameModule {
  type Rdf = BlazeSesame
  implicit val ct = classTag[Rdf#Triple]
}

• Once there, the flatMap function called within main function would automatically take the implicit ctt value as the ClassTag for the return type RDF#Triple