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