pre pre_deleteSomeElements
{
	"\n\nBefore the operation: ".println();
	printStatistics();
	
	deleteExceptionalElements();
}

post post_deleteSomeElements
{
	"\n\nAfter the operation: ".println();
	printStatistics();	
}

//Prints the statistics of the 
operation printStatistics()
{
	("Number of exceptional elements: " + InModel!ExceptionalElements.allInstances().size() + "").println();
}

===== Run 1 =====
Before the operation: 
Number of exceptional edges: 35

After the operation: 
Number of exceptional edges: 35

===== Run 2 =====
Before the operation: 
Number of exceptional edges: 0

After the operation: 
Number of exceptional edges: 0

abstract class OwnerElement
{
		property outEdges#start : Element[*] { ordered composes };
		property inEdges#end : Element[*] { ordered };
		
		//... some properties and attributes		
}

abstract class Element
{
	property start#outEdges : OwnerElement[1];
	property end#inEdges : OwnerElement[1];
}

class ExceptionalElement extends Element
{
	property details : ExceptionalElementDetails[1];
}

class ExceptionalElementDetails
{
	//... some properties and attributes
}

//Delete ExceptionalElements instances
operation deleteExceptionalElements()
{
	//Getting all the exceptional elements as a list
	var exceptionalElementsList = InModel!ExceptionalElement.allInstances();
	
	//Setting the start reference to null to remove the containment reference
	for(ee:InModel!ExceptionalElement in exceptionalElementsList)
	{
		ee.start = null;		
	}
	
	//Deleting the exceptional elements one by one
	while(not eexceptionalElementsList.isEmpty())
	{
		var ee = exceptionalElementsList.removeAt(exceptionalElementsList.size()-1);
		delete ee;
	}	
}

delete InModel!ExceptionalElement.allInstances();