Buildmetadata-Plugin executed multiple times

The buildmetadata plugin ist executed multiple times according to the messages written to the console during the execution of the build 'site' (relevant lines marked with "##"):

[INFO] Preparing surefire-report:report

1. 1. [INFO] [buildmetadata:provide-buildmetadata {execution: default}

      ]

   2. [INFO] Reusing previously built metadata file.
      [INFO] [resources:resources {execution: default-resources}

      ]
      [INFO] Using 'UTF-8' encoding to copy filtered resources.
      [INFO] skip non existing resourceDirectory D:\Projekte\workspaces\smartics\deployment-metadata\src\main\resources
      [INFO] [compiler:compile

      {execution: default-compile}

      ]
      [INFO] Nothing to compile - all classes are up to date
      [INFO] [resources:testResources

      {execution: default-testResources}

      ]
      [INFO] Using 'UTF-8' encoding to copy filtered resources.
      [INFO] skip non existing resourceDirectory D:\Projekte\workspaces\smartics\deployment-metadata\src\test\resources
      [INFO] [compiler:testCompile

      {execution: default-testCompile}

      ]
      [INFO] No sources to compile
      [INFO] [surefire:test

      {execution: default-test}

      ]
      [INFO] No tests to run.
      [INFO] Preparing surefire-report:report-only
      [INFO] No goals needed for project - skipping
      [INFO] Preparing javadoc:javadoc

   3. [INFO] [buildmetadata:provide-buildmetadata {execution: default}

      ]
      [INFO] Preparing javadoc:test-javadoc

   4. [INFO] [buildmetadata:provide-buildmetadata {execution: default}

      ]
      [INFO] [resources:resources

      {execution: default-resources}

      ]
      [INFO] Using 'UTF-8' encoding to copy filtered resources.
      [INFO] skip non existing resourceDirectory D:\Projekte\workspaces\smartics\deployment-metadata\src\main\resources
      [INFO] [compiler:compile

      {execution: default-compile}

      ]
      [INFO] Nothing to compile - all classes are up to date
      [INFO] Preparing jdepend:generate

   5. [INFO] [buildmetadata:provide-buildmetadata {execution: default}

      ]
      [INFO] [resources:resources

      {execution: default-resources}

      ]
      [INFO] Using 'UTF-8' encoding to copy filtered resources.
      [INFO] skip non existing resourceDirectory D:\Projekte\workspaces\smartics\deployment-metadata\src\main\resources
      [INFO] [compiler:compile

      {execution: default-compile}

      ]
      [INFO] Nothing to compile - all classes are up to date
      [INFO] Preparing findbugs:findbugs

   6. [INFO] [buildmetadata:provide-buildmetadata {execution: default}

      ]
      [INFO] [resources:resources

      {execution: default-resources}

      ]
      [INFO] Using 'UTF-8' encoding to copy filtered resources.
      [INFO] skip non existing resourceDirectory D:\Projekte\workspaces\smartics\deployment-metadata\src\main\resources
      [INFO] [compiler:compile

      {execution: default-compile}

      ]
      [INFO] Nothing to compile - all classes are up to date
      [INFO] Preparing cobertura:cobertura

   7. [INFO] [buildmetadata:provide-buildmetadata {execution: default}

      ]
      [INFO] [resources:resources

      {execution: default-resources}

      ]
      [INFO] Using 'UTF-8' encoding to copy filtered resources.
      [INFO] skip non existing resourceDirectory D:\Projekte\workspaces\smartics\deployment-metadata\src\main\resources
      [INFO] [compiler:compile

      {execution: default-compile}

      ]
      [INFO] Nothing to compile - all classes are up to date
      [INFO] [cobertura:instrument

      {execution: default-instrument}

      ]
      [INFO] [resources:testResources

      {execution: default-testResources}

      ]
      [INFO] Using 'UTF-8' encoding to copy filtered resources.
      [INFO] skip non existing resourceDirectory D:\Projekte\workspaces\smartics\deployment-metadata\src\test\resources
      [INFO] [compiler:testCompile

      {execution: default-testCompile}

      ]
      [INFO] No sources to compile
      [INFO] [surefire:test

      {execution: default-test}

      ]
      [INFO] No tests to run.
      [INFO] [site:site

      {execution: default-site}

      ]