private boolean isMetaProperty(Label type, ColumnNode alignmentColumnNode) {
   // Check for the case of DataPropertyOfColumnLink and ColumnSubClassLink
   boolean case1 =
       (type.getUri().equals(DataPropertyOfColumnLink.getFixedLabel().getUri())
           || type.getUri().equals(ColumnSubClassLink.getFixedLabel().getUri()));
   if (case1) return true;
   Set<LabeledLink> incomingLinks =
       alignment.getCurrentIncomingLinksToNode(alignmentColumnNode.getId());
   if (incomingLinks != null && !incomingLinks.isEmpty()) {
     LabeledLink incomingLink = incomingLinks.iterator().next();
     if (incomingLink != null
         && (incomingLink instanceof ClassInstanceLink)
         && incomingLink.getKeyType().equals(LinkKeyInfo.UriOfInstance)) return true;
   }
   return false;
 }
  @Override
  public void generateJson(String prefix, PrintWriter pw, VWorkspace vWorkspace) {
    VWorksheet vWorksheet = vWorkspace.getViewFactory().getVWorksheetByWorksheetId(worksheetId);
    List<String> hNodeIdList = new ArrayList<String>();
    List<HNodePath> columns = vWorksheet.getColumns();
    for (HNodePath path : columns) hNodeIdList.add(path.getLeaf().getId());
    String alignmentId =
        AlignmentManager.Instance()
            .constructAlignmentId(vWorkspace.getWorkspace().getId(), vWorksheet.getWorksheetId());

    JSONObject topObj = new JSONObject();
    try {
      topObj.put(
          GenericJsonKeys.updateType.name(), AlignmentSVGVisualizationUpdate.class.getSimpleName());
      topObj.put(JsonKeys.alignmentId.name(), alignmentId);
      topObj.put(JsonKeys.worksheetId.name(), worksheetId);

      // Using Mohsen's GraphUtils method for graph traversal
      HashMap<Node, Integer> nodeHeightsMap = GraphUtil.levelingCyclicGraph(alignmentGraph);
      HashMap<Node, Set<ColumnNode>> nodeCoverage =
          GraphUtil.getNodesCoverage(alignmentGraph, nodeHeightsMap);
      /** Identify the max height * */
      int maxTreeHeight = 0;
      for (Node node : nodeHeightsMap.keySet()) {
        if (nodeHeightsMap.get(node) >= maxTreeHeight) {
          maxTreeHeight = nodeHeightsMap.get(node);
        }
      }

      /** * Add the nodes and the links from the Steiner tree ** */
      List<String> hNodeIdsAdded = new ArrayList<String>();
      JSONArray nodesArr = new JSONArray();
      JSONArray linksArr = new JSONArray();

      if (alignmentGraph != null && alignmentGraph.vertexSet().size() != 0) {
        /** Add the nodes * */
        Set<Node> nodes = alignmentGraph.vertexSet();
        HashMap<Node, Integer> verticesIndex = new HashMap<Node, Integer>();
        int nodesIndexcounter = 0;
        for (Node node : nodes) {
          /** Get info about the nodes that this node covers or sits above * */
          int height = maxTreeHeight - nodeHeightsMap.get(node);

          /** Add the hnode ids of the columns that this vertex covers * */
          JSONArray hNodeIdsCoveredByVertex = new JSONArray();
          for (Node v : nodeCoverage.get(node)) {
            if (v instanceof ColumnNode) {
              ColumnNode cNode = (ColumnNode) v;
              hNodeIdsCoveredByVertex.put(cNode.getHNodeId());
            }
          }

          String hNodeId = "";

          /** Add the semantic type information * */
          if (node instanceof ColumnNode) {
            ColumnNode cNode = (ColumnNode) node;
            hNodeId = cNode.getHNodeId();
            hNodeIdsAdded.add(cNode.getHNodeId());
          }
          JSONObject nodeObj =
              getNodeJsonObject(
                  node.getLocalId(),
                  node.getId(),
                  node.getType().name(),
                  height,
                  hNodeIdsCoveredByVertex,
                  hNodeId);
          nodesArr.put(nodeObj);
          verticesIndex.put(node, nodesIndexcounter++);
        }

        /** * Add the links ** */
        Set<Link> links = alignmentGraph.edgeSet();
        for (Link link : links) {
          Node source = link.getSource();
          Integer sourceIndex = verticesIndex.get(source);
          Node target = link.getTarget();
          Integer targetIndex = verticesIndex.get(target);
          Set<Link> outEdges = alignmentGraph.outgoingEdgesOf(target);

          if (sourceIndex == null || targetIndex == null) {
            logger.error("Edge vertex index not found!");
            continue;
          }

          JSONObject linkObj = new JSONObject();
          linkObj.put(JsonKeys.source.name(), sourceIndex);
          linkObj.put(JsonKeys.target.name(), targetIndex);
          linkObj.put(JsonKeys.sourceNodeId.name(), source.getId());
          linkObj.put(JsonKeys.targetNodeId.name(), target.getId());

          linkObj.put(JsonKeys.label.name(), link.getLabel().getLocalName());
          linkObj.put(JsonKeys.id.name(), link.getId() + "");
          linkObj.put(JsonKeys.linkStatus.name(), link.getStatus().name());
          linkObj.put(JsonKeys.linkUri.name(), link.getLabel().getUri());

          if (target.getType() == NodeType.ColumnNode && outEdges.isEmpty()) {
            linkObj.put(JsonKeys.linkType.name(), JsonValues.holderLink.name());
            if (link.getKeyType() == LinkKeyInfo.PartOfKey)
              linkObj.put(JsonKeys.label.name(), link.getLabel().getLocalName() + "*");
          }

          linksArr.put(linkObj);

          if (link.getType() == LinkType.ClassInstanceLink
              && link.getKeyType() == LinkKeyInfo.PartOfKey
              && target instanceof ColumnNode) {
            ColumnNode cNode = (ColumnNode) target;
            // Add the holder vertex object and the link that attaches nodes to the columns
            JSONArray hNodeIdsCoveredByVertex_holder = new JSONArray();
            hNodeIdsCoveredByVertex_holder.put(cNode.getHNodeId());

            JSONObject vertObj_holder =
                getNodeJsonObject(
                    JsonValues.key.name(),
                    source.getId() + "_holder",
                    NodeType.ColumnNode.name(),
                    0,
                    hNodeIdsCoveredByVertex_holder,
                    cNode.getHNodeId());
            nodesArr.put(vertObj_holder);
            nodesIndexcounter++;

            // Add the holder link
            JSONObject linkObj_holder =
                getLinkJsonObject(
                    JsonValues.key.name(),
                    "",
                    nodesIndexcounter,
                    nodesIndexcounter - 1,
                    "",
                    "",
                    "",
                    "");
            linksArr.put(linkObj_holder);
          }

          if (link.getType() == LinkType.DataPropertyOfColumnLink) {
            DataPropertyOfColumnLink dpLink = (DataPropertyOfColumnLink) link;
            String startHNodeId = dpLink.getSpecializedColumnHNodeId();

            // Get height of the class instance node
            int height = maxTreeHeight - nodeHeightsMap.get(link.getSource());

            // Add 2 more holder nodes
            // Start node
            JSONArray hNodeIdsCoveredByVertex_holder = new JSONArray();
            hNodeIdsCoveredByVertex_holder.put(startHNodeId);
            JSONObject startNode =
                getNodeJsonObject(
                    "",
                    source.getId() + "_holder",
                    JsonValues.DataPropertyOfColumnHolder.name(),
                    height - 0.35,
                    hNodeIdsCoveredByVertex_holder,
                    startHNodeId);
            nodesArr.put(startNode);

            nodesIndexcounter++;

            // End node
            String endHNodeId = ((ColumnNode) link.getTarget()).getHNodeId();
            JSONArray hNodeIdsCoveredByVertex_holder_2 = new JSONArray();
            hNodeIdsCoveredByVertex_holder_2.put(endHNodeId);
            JSONObject endNode =
                getNodeJsonObject(
                    "",
                    target.getId() + "_holder",
                    JsonValues.DataPropertyOfColumnHolder.name(),
                    height - 0.35,
                    hNodeIdsCoveredByVertex_holder_2,
                    endHNodeId);
            nodesArr.put(endNode);

            nodesIndexcounter++;

            // Add the horizontal link
            JSONObject linkObj_holder =
                getLinkJsonObject(
                    "",
                    "",
                    nodesIndexcounter - 2,
                    nodesIndexcounter - 1,
                    JsonValues.horizontalDataPropertyLink.name(),
                    "",
                    "",
                    "");
            linksArr.put(linkObj_holder);
          } else if (link.getType() == LinkType.ObjectPropertySpecializationLink) {
            ObjectPropertySpecializationLink opLink = (ObjectPropertySpecializationLink) link;
            Link specializedLink = opLink.getSpecializedLink();

            // Get height of the class instance node
            int height = nodeHeightsMap.get(specializedLink.getTarget());

            // Add 2 more holder nodes
            // Start node
            JSONArray hNodeIdsCoveredByVertex_holder = new JSONArray();
            for (Node v : nodeCoverage.get(specializedLink.getTarget())) {
              if (v instanceof ColumnNode) {
                ColumnNode cNode = (ColumnNode) v;
                hNodeIdsCoveredByVertex_holder.put(cNode.getHNodeId());
              }
            }
            JSONObject startNode =
                getNodeJsonObject(
                    "",
                    source.getId() + "_holder",
                    JsonValues.DataPropertyOfColumnHolder.name(),
                    height + 0.65,
                    hNodeIdsCoveredByVertex_holder,
                    "");
            nodesArr.put(startNode);

            nodesIndexcounter++;

            // End node
            String endHNodeId = ((ColumnNode) link.getTarget()).getHNodeId();
            JSONArray hNodeIdsCoveredByVertex_holder_2 = new JSONArray();
            hNodeIdsCoveredByVertex_holder_2.put(endHNodeId);
            JSONObject endNode =
                getNodeJsonObject(
                    "",
                    target.getId() + "_holder",
                    JsonValues.DataPropertyOfColumnHolder.name(),
                    height + 0.65,
                    hNodeIdsCoveredByVertex_holder_2,
                    endHNodeId);
            nodesArr.put(endNode);

            nodesIndexcounter++;

            // Add the horizontal link
            JSONObject linkObj_holder =
                getLinkJsonObject(
                    "",
                    "",
                    nodesIndexcounter - 2,
                    nodesIndexcounter - 1,
                    JsonValues.horizontalDataPropertyLink.name(),
                    "",
                    "",
                    "");
            linksArr.put(linkObj_holder);
          }

          linkObj.put(JsonKeys.linkType.name(), link.getType());
        }
      }

      // Add the vertices for the columns that were not in Steiner tree
      hNodeIdList.removeAll(hNodeIdsAdded);
      for (String hNodeId : hNodeIdList) {
        JSONArray hNodeIdsCoveredByVertex = new JSONArray();
        hNodeIdsCoveredByVertex.put(hNodeId);
        JSONObject vertObj =
            getNodeJsonObject(
                "", hNodeId, JsonValues.Unassigned.name(), 0, hNodeIdsCoveredByVertex, hNodeId);
        nodesArr.put(vertObj);
      }

      topObj.put(JsonKeys.maxTreeHeight.name(), maxTreeHeight);
      topObj.put(JsonKeys.nodes.name(), nodesArr);
      topObj.put(JsonKeys.links.name(), linksArr);

      pw.write(topObj.toString());
    } catch (JSONException e) {
      logger.error("Error occured while writing JSON!", e);
    }
  }