@Override
  public IfcModelInterface execute()
      throws UserException, BimserverLockConflictException, BimserverDatabaseException {
    User user = getUserByUoid(getAuthorization().getUoid());
    Set<String> foundNames = new HashSet<String>();
    IfcModelSet ifcModelSet = new IfcModelSet();
    Project project = null;
    long incrSize = 0L;

    SerializerPluginConfiguration serializerPluginConfiguration =
        getDatabaseSession()
            .get(
                StorePackage.eINSTANCE.getSerializerPluginConfiguration(),
                serializerOid,
                Query.getDefault());

    for (Long roid : roids) {
      Revision virtualRevision = getRevisionByRoid(roid);
      project = virtualRevision.getProject();
      if (!getAuthorization().hasRightsOnProjectOrSuperProjectsOrSubProjects(user, project)) {
        throw new UserException(
            "User has insufficient rights to download revisions from this project");
      }
      Map<ConcreteRevision, Set<Long>> map = new HashMap<ConcreteRevision, Set<Long>>();
      for (String name : names) {
        if (!foundNames.contains(name)) {
          for (ConcreteRevision concreteRevision : virtualRevision.getConcreteRevisions()) {
            for (ObjectIdentifier objectIdentifier :
                getDatabaseSession()
                    .getOidsOfName(
                        name, concreteRevision.getProject().getId(), concreteRevision.getId())) {
              foundNames.add(name);
              if (!map.containsKey(concreteRevision)) {
                map.put(concreteRevision, new HashSet<Long>());
                incrSize += concreteRevision.getSize();
              }
              map.get(concreteRevision).add(objectIdentifier.getOid());
            }
          }
        }
      }
      final long totalSize = incrSize;
      final AtomicLong total = new AtomicLong();

      for (ConcreteRevision concreteRevision : map.keySet()) {
        IfcModel subModel = new IfcModel();
        int highestStopId = findHighestStopRid(project, concreteRevision);
        Query query =
            new Query(
                concreteRevision.getProject().getId(),
                concreteRevision.getId(),
                objectIDM,
                deep,
                highestStopId);
        subModel.addChangeListener(
            new IfcModelChangeListener() {
              @Override
              public void objectAdded() {
                total.incrementAndGet();
                progress = (int) Math.round(100.0 * total.get() / totalSize);
              }
            });
        Set<Long> oids = map.get(concreteRevision);
        getDatabaseSession().getMapWithOids(subModel, oids, query);
        subModel.getModelMetaData().setDate(concreteRevision.getDate());

        try {
          checkGeometry(
              serializerPluginConfiguration,
              bimServer.getPluginManager(),
              subModel,
              project,
              concreteRevision,
              virtualRevision);
        } catch (GeometryGeneratingException e) {
          throw new UserException(e);
        }

        ifcModelSet.add(subModel);
      }
    }
    IfcModelInterface ifcModel = new IfcModel();
    try {
      ifcModel =
          bimServer
              .getMergerFactory()
              .createMerger(getDatabaseSession(), getAuthorization().getUoid())
              .merge(project, ifcModelSet, new ModelHelper(ifcModel));
      ifcModel.getModelMetaData().setName("query");
      for (String name : names) {
        if (!foundNames.contains(name)) {
          throw new UserException("Name " + name + " not found");
        }
      }
      ifcModel.getModelMetaData().setRevisionId(1);
      ifcModel
          .getModelMetaData()
          .setAuthorizedUser(getUserByUoid(getAuthorization().getUoid()).getName());
      ifcModel.getModelMetaData().setDate(new Date());
      return ifcModel;
    } catch (MergeException e) {
      throw new UserException(e);
    }
  }
  private IfcModel realCheckout(
      Project project, Revision revision, DatabaseSession databaseSession, User user)
      throws BimserverLockConflictException, BimserverDatabaseException, UserException {
    SerializerPluginConfiguration serializerPluginConfiguration =
        getDatabaseSession()
            .get(
                StorePackage.eINSTANCE.getSerializerPluginConfiguration(),
                serializerOid,
                Query.getDefault());
    final long totalSize = revision.getSize();
    final AtomicLong total = new AtomicLong();

    IfcModelSet ifcModelSet = new IfcModelSet();
    for (ConcreteRevision subRevision : revision.getConcreteRevisions()) {
      IfcModel subModel = new IfcModel();
      int highestStopId = findHighestStopRid(project, subRevision);
      Query query =
          new Query(
              subRevision.getProject().getId(), subRevision.getId(), null, Deep.YES, highestStopId);
      subModel.addChangeListener(
          new IfcModelChangeListener() {
            @Override
            public void objectAdded() {
              total.incrementAndGet();
              if (totalSize == 0) {
                setProgress("Preparing checkout...", 0);
              } else {
                setProgress(
                    "Preparing checkout...", (int) Math.round(100.0 * total.get() / totalSize));
              }
            }
          });
      getDatabaseSession().getMap(subModel, query);
      try {
        checkGeometry(
            serializerPluginConfiguration,
            getBimServer().getPluginManager(),
            subModel,
            project,
            subRevision,
            revision);
      } catch (GeometryGeneratingException e) {
        throw new UserException(e);
      }
      subModel.getModelMetaData().setDate(subRevision.getDate());
      ifcModelSet.add(subModel);
    }

    IfcModelInterface ifcModel = new IfcModel();
    if (ifcModelSet.size() > 1) {
      try {
        ifcModel =
            getBimServer()
                .getMergerFactory()
                .createMerger(getDatabaseSession(), getAuthorization().getUoid())
                .merge(revision.getProject(), ifcModelSet, new ModelHelper(ifcModel));
      } catch (MergeException e) {
        throw new UserException(e);
      }
    } else {
      ifcModel = ifcModelSet.iterator().next();
    }

    ifcModel.getModelMetaData().setName(project.getName() + "." + revision.getId());
    ifcModel.getModelMetaData().setRevisionId(project.getRevisions().indexOf(revision) + 1);
    ifcModel.getModelMetaData().setAuthorizedUser(user.getName());
    ifcModel.getModelMetaData().setDate(new Date());
    return (IfcModel) ifcModel;
  }