[news.eclipse.tools.uml2] ConnectableElement in sequence diagram

[Greg O'Keefe <greg.okeefe@xxxxxxxxxx>]

I am trying to make a model which includes a sequence diagram 
(Interaction).  The Lifelines are intended to represent objects.  But 
each Lifeline "represents" a ConnectableElement, and it is the "type" of 
this which gives the class of the Lifelines object.  The only concrete 
immediate subclasses of ConnectableElement are Property and Parameter.

So, the Lifeline must "represent" a Property, but my question is, a 
Property of what?  (or similarly with Parameter)  Do I need to add an 
ad-hoc Classifier and Property to the model for this purpose?