public XmlElement AddLifelineElement(XmlElement parentElement,XmlElement collaborationElement,Process lifelineItem)
{
LifelineElementCreator elementCreator=new LifelineElementCreator(xmiDocument,this);
XmlElement newLifelineElement=elementCreator.CreateLifelineElement(parentElement,collaborationElement,lifelineItem);
return newLifelineElement;
}