diff --git a/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/controller/admin/WorkerController.scala b/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/controller/admin/WorkerController.scala
index f704f36..3c369af 100644
--- a/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/controller/admin/WorkerController.scala
+++ b/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/controller/admin/WorkerController.scala
@@ -1,7 +1,7 @@
 package org.dbpedia.databus_mods.server.core.controller.admin
 
 import com.fasterxml.jackson.annotation.JsonView
-import org.dbpedia.databus_mods.server.core.persistence.WorkerRepository
+import org.dbpedia.databus_mods.server.core.persistence.WorkerRepo
 import org.dbpedia.databus_mods.server.core.views.Views
 import org.slf4j.LoggerFactory
 import org.springframework.beans.factory.annotation.Autowired
@@ -13,7 +13,7 @@ class WorkerController {
 
   private val log = LoggerFactory.getLogger(classOf[WorkerController])
 
-  @Autowired private var workerRepository: WorkerRepository = _
+  @Autowired private var workerRepository: WorkerRepo = _
 
   @JsonView(value = Array(classOf[Views.PublicWorkerView]))
   @RequestMapping(value = Array(), method = Array(RequestMethod.GET, RequestMethod.DELETE, RequestMethod.POST))
diff --git a/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/execution/Singleton.scala b/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/execution/Singleton.scala
new file mode 100644
index 0000000..cd69766
--- /dev/null
+++ b/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/execution/Singleton.scala
@@ -0,0 +1,12 @@
+package org.dbpedia.databus_mods.server.core.execution
+
+import org.dbpedia.databus_mods.server.core.service.{MetadataService, TaskService}
+
+
+object Singleton {
+
+  var taskService: TaskService = _
+
+  var metadataService: MetadataService = _
+
+}
\ No newline at end of file
diff --git a/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/execution/WorkerThread.scala b/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/execution/WorkerThread.scala
index ffab996..cff1dd1 100644
--- a/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/execution/WorkerThread.scala
+++ b/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/execution/WorkerThread.scala
@@ -4,6 +4,7 @@ import org.dbpedia.databus.mods.core.worker.api.ModActivityClientHttp
 import org.dbpedia.databus_mods.server.core.persistence.{Task, TaskStatus, Worker}
 import org.dbpedia.databus_mods.server.core.service.TaskService
 import org.slf4j.LoggerFactory
+//import org.dbpedia.databus_mods.server.core.execution.Singleton
 
 import java.net.URI
 
diff --git a/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/persistence/Task.scala b/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/persistence/Task.scala
index 6c9e98b..eb9d084 100644
--- a/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/persistence/Task.scala
+++ b/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/persistence/Task.scala
@@ -19,7 +19,7 @@ class Task
   @(JoinColumn@field)(name = "databusFile_id")
   @BeanProperty
   @(JsonView@field)(value = Array(classOf[Views.PublicTaskView]))
-  var databusFile: DatabusFile,
+  var databusFile: DataIdPart,
   @(ManyToOne@field)(fetch = FetchType.EAGER)
   @BeanProperty
   @(JsonView@field)(value = Array(classOf[Views.PublicTaskView], classOf[Views.DatabusFileView]))
@@ -31,10 +31,10 @@ class Task
   @(JsonView@field)(value = Array(classOf[Views.Default]))
   var id: Long = _
 
-  @PreRemove
-  def removeTaskFromDatabusFile(): Unit = {
-    databusFile.getTasks.remove(this)
-  }
+//  @PreRemove
+//  def removeTaskFromDatabusFile(): Unit = {
+//    databusFile.getTasks.remove(this)
+//  }
 
   //  @BeanProperty
   //  var uri: String = _
diff --git a/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/service/DatabusFileService.scala b/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/service/DatabusFileService.scala
index ba20429..e8e0cf4 100644
--- a/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/service/DatabusFileService.scala
+++ b/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/service/DatabusFileService.scala
@@ -3,13 +3,13 @@ package org.dbpedia.databus_mods.server.core.service
 import java.util.Optional
 import java.util
 
-import org.dbpedia.databus_mods.server.core.persistence.{DatabusFile, DatabusFileRepository}
+import org.dbpedia.databus_mods.server.core.persistence.{DataIdPart, DataIdPartRepo}
 import org.springframework.stereotype.Service
 
 @Service
-class DatabusFileService(databusFileRepository: DatabusFileRepository) {
+class DatabusFileService(databusFileRepository: DataIdPartRepo) {
 
-  def add(df: DatabusFile): Unit = {
+  def add(df: DataIdPart): Unit = {
     val databusFile = databusFileRepository.findByDataIdSingleFileAndChecksum(df.dataIdSingleFile, df.checksum)
     if(databusFile.isPresent) {
       df.copyOf(databusFile.get)
@@ -18,11 +18,11 @@ class DatabusFileService(databusFileRepository: DatabusFileRepository) {
     }
   }
 
-  def get(databusId: String, checksum: String): Optional[DatabusFile] = {
+  def get(databusId: String, checksum: String): Optional[DataIdPart] = {
     databusFileRepository.findByDataIdSingleFileAndChecksum(databusId,checksum)
   }
 
-  def getAll: util.Iterator[DatabusFile] = {
+  def getAll: util.Iterator[DataIdPart] = {
     databusFileRepository.findAll().iterator()
   }
 }
diff --git a/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/service/ModService.scala b/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/service/ModService.scala
index f1f3d10..7c7c3e0 100644
--- a/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/service/ModService.scala
+++ b/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/service/ModService.scala
@@ -3,7 +3,7 @@ package org.dbpedia.databus_mods.server.core.service
 import java.util
 import java.util.Optional
 
-import org.dbpedia.databus_mods.server.core.persistence.{Mod, ModRepository, Worker, WorkerRepository}
+import org.dbpedia.databus_mods.server.core.persistence.{Mod, ModRepository, Worker, WorkerRepo}
 import org.slf4j.LoggerFactory
 import org.springframework.beans.factory.annotation.Autowired
 import org.springframework.stereotype.Service
@@ -18,7 +18,7 @@ class ModService {
 
   @Autowired private var modRepository: ModRepository = _
 
-  @Autowired private var workerRepository: WorkerRepository = _
+  @Autowired private var workerRepository: WorkerRepo = _
 
   def add(m: Mod): Unit = {
     val mod = modRepository.findByName(m.name)
diff --git a/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/service/WorkerService.scala b/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/service/WorkerService.scala
index 92ef140..a70dd82 100644
--- a/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/service/WorkerService.scala
+++ b/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/service/WorkerService.scala
@@ -4,14 +4,14 @@ import java.util
 import java.util.Optional
 
 import org.dbpedia.databus_mods.server.core.execution.{WorkerThreadExceptionHandler, WorkerThreadPool}
-import org.dbpedia.databus_mods.server.core.persistence.{Worker, WorkerRepository}
+import org.dbpedia.databus_mods.server.core.persistence.{Worker, WorkerRepo}
 import org.springframework.stereotype.Service
 
 
 @Service
 class WorkerService(
                      workerThreadPool: WorkerThreadPool,
-                     workerRepository: WorkerRepository, taskService: TaskService) {
+                     workerRepository: WorkerRepo, taskService: TaskService) {
 
   def add(w: Worker): Unit = {
     val worker = workerRepository.findByUrl(w.getUrl)
diff --git a/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/utils/DatabusQueryUtil.scala b/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/utils/DatabusQueryUtil.scala
index dda105d..af7dbea 100644
--- a/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/utils/DatabusQueryUtil.scala
+++ b/databus-mods-server/databus-mods-server-core/src/main/scala/org/dbpedia/databus_mods/server/core/utils/DatabusQueryUtil.scala
@@ -3,16 +3,16 @@ package org.dbpedia.databus_mods.server.core.utils
 import java.sql.Timestamp
 
 import org.apache.jena.query.{QueryExecutionFactory, QueryFactory, Syntax}
-import org.dbpedia.databus_mods.server.core.persistence.DatabusFile
+import org.dbpedia.databus_mods.server.core.persistence.DataIdPart
 
 import scala.collection.mutable.ArrayBuffer
 
 object DatabusQueryUtil {
 
-  def getUpdates(query: String, endpoint: String): Array[DatabusFile] = {
+  def getUpdates(query: String, endpoint: String): Array[DataIdPart] = {
     val limit = 10000
     var responseSize, offset = 0
-    val databusFilesBuffer = new ArrayBuffer[DatabusFile]()
+    val databusFilesBuffer = new ArrayBuffer[DataIdPart]()
 
     do {
       responseSize = 0
@@ -26,7 +26,7 @@ object DatabusQueryUtil {
         responseSize += 1
         val qs = resultSet.next()
         databusFilesBuffer.append(
-          new DatabusFile(
+          new DataIdPart(
             qs.getResource("file").getURI,
             qs.getResource("downloadURL").getURI,
             qs.getLiteral("sha256sum").getLexicalForm,
@@ -40,7 +40,7 @@ object DatabusQueryUtil {
     databusFilesBuffer.toArray
   }
 
-  def queryDatabusFileByURI(uri: String, endpoint: String): Option[DatabusFile] = {
+  def queryDatabusFileByURI(uri: String, endpoint: String): Option[DataIdPart] = {
     val query =
       s"""PREFIX dataid: <http://dataid.dbpedia.org/ns/core#>
          |PREFIX dct:    <http://purl.org/dc/terms/>
@@ -58,7 +58,7 @@ object DatabusQueryUtil {
     val resultSet = queryExec.execSelect()
     val possibleDatabusFile = if (resultSet.hasNext) {
       val qs = resultSet.next()
-      Some(new DatabusFile(
+      Some(new DataIdPart(
         uri,
         qs.getResource("downloadURL").getURI,
         qs.getLiteral("sha256sum").getLexicalForm,