### Registration for Repository Objects
Custom Meta Data usage in Repository Objects needs to be registered
in their respective *module.xml* by adding the xml attribute *amet* to the 
*object* element.
```xml
...
<objects>
    <object ... id="grp" amet="1"
    ...
</objects>
...
```

The responsible GUI class for presenting the main features like *Settings* 
*Info-Screen* should provide a meta data tab and forward the meta data related 
commands to *ilObjectMetaDataGUI*.


```<?php declare(strict_types=1);

/*
 * ...
 * @ilCtrl_Calls ilObjGroupGUI:ilObjectMetaDataGUI
 * ...
 */
class ilObjXXXGUI extends ilObject2GUI 
{
	// Add meta data tab
	/**
	 * @inheritdoc
	 */
	protected function getTabs() 
	{
		global $DIC;
		
		if ($DIC->access()->checkAccess('write','',$this->ref_id))
		{
			$mdgui = new ilObjectMetaDataGUI($this->object);
			$mdtab = $mdgui->getTab();
			if($mdtab !== null)
			{
				$this->tabs_gui->addTab(
					"meta_data",
					$DIC->language()->txt('meta_data'),
					$mdtab,
					"",
					"ilobjectmetadatagui"
				);
			}
		}
	}
	//...
	// forward to meta data gui
	public function executeCommand() 
	{
		// ...
		switch($next_class) {
			
			case 'ilobjectmetadatagui';
				$this->tabs_gui->activateTab('meta_data');
				$md_gui = new ilObjectMetaDataGUI($this->object);	
				$this->ctrl->forwardCommand($md_gui);
				break;
		}
	}
}

```

### Known Issues

Display options don't respect the scope of the Metadata set, the
respective fields are also shown outside of the scope.

Fixing this is risky in terms of performance, if this is fixed in
the future the scope should probably be preloaded. See
`ilAdvancedMDSubstitution::getParsedSubstitutions` and
`ilAdvancedMDValues::preloadedRead`.