--- a/src/main/scala/SparqlToSparqlToSql.scala	Sun Feb 28 15:05:33 2010 -0500
+++ b/src/main/scala/SparqlToSparqlToSql.scala	Sun Feb 28 15:07:28 2010 -0500
@@ -18,29 +18,38 @@
 
       /* ... turn each triple pattern in the rule heads into a SQL pattern. */
       rule.head.triplepatterns.foldLeft(allgps)((gps, triple) => {
+	def substituteVar (term:sparql.Term, label:String):(sparql.Term, List[sparql.Var], List[sql.NamedAttribute]) = {
+	  term match {
+	    case sparql.TermUri(u) => (term, List[sparql.Var](), List(
+	      sql.NamedAttribute(sql.PrimaryExpressionTyped(sql.Datatype.STRING,sql.Name(u.toString)),
+				 sql.AttrAlias(sql.Name(label)))))
+	    case sparql.TermVar(v) => (sparql.TermVar(sparql.Var(label)), List(sparql.Var(label)), List[sql.NamedAttribute]())
+	    case sparql.TermLit(l) => (term, List[sparql.Var](), List(
+	      sql.NamedAttribute(sql.PrimaryExpressionTyped(sql.Datatype.STRING,sql.Name(l.toString)),
+				 sql.AttrAlias(sql.Name(label)))))
+	  }
+	}
+
+	/* Add constant for predicate into selects. */
 
 	/* Substituted SPARQL ?S and ?O into the triple pattern. */
-	val s = sparql.Var("S");
-	val o = sparql.Var("O")
+	val (s, sselects, sconsts) = substituteVar(triple.s, "S");
+	val (p, pselects, pconsts) = substituteVar(triple.p, "P");
+	val (o, oselects, oconsts) = substituteVar(triple.o, "O");
 	val select = sparql.Select(
-	  sparql.SparqlAttributeList(List(s, o)),
-	  sparql.TriplesBlock(
-	    List(sparql.TriplePattern(sparql.TermVar(s), triple.p, sparql.TermVar(o)))))
+	  sparql.SparqlAttributeList(sselects ++ pselects ++ oselects),
+	  sparql.TriplesBlock(List(sparql.TriplePattern(s, p, o)))
+	)
 
 	/* Convert to equivalent SQL SELECT. */
 	val asStem = sparql2sparql.SparqlToSparql(select, List(rule))
+	// println("triple: "+triple)
+	// println("asStem: "+asStem)
 	val sql.Select(sql.AttributeList(attributes), tablelist, expression) = sparql2sql.SparqlToSql(schema, asStem, stemUri, false, true)
-
-	/* Add constant for predicate into selects. */
-	val p = triple.p match {
-	  case sparql.TermUri(u) => sql.NamedAttribute(sql.PrimaryExpressionTyped(sql.Datatype.STRING,sql.Name("<" + u.s + ">")),
-						       sql.AttrAlias(sql.Name("P")))
-	  case sparql.TermVar(v) => error("triplification algorithm doesn't handly variable predicate in " + triple)
-	  case sparql.TermLit(_) => error("illegal literal in predicate position of " + triple)
-	}
+	// println("SQL: "+sql.Select(sql.AttributeList(attributes ++ sconsts ++ pconsts ++ oconsts), tablelist, expression))
 
 	/* Add resulting SELECT to list of graph patterns. */
-	gps :+ sql.Select(sql.AttributeList(attributes + p), tablelist, expression)
+	gps :+ sql.Select(sql.AttributeList(attributes ++ sconsts ++ pconsts ++ oconsts), tablelist, expression)
       })
     })