/** Only works wiht m to n relationships to & through pntDbObjects 
	* with id properties corrsponding to the steps and mapped to the database
	* The path should not refer to the mToNproperty but to the corresponding 1ToNproperty
	* whose type corresponds to the JOINed table, and from there to the nTo1property 
	* on that type.  
	* For example if the name of $mToNproperty is 'keywords', wich gives
	* access to an array of objects of type Keyword. The path could then be 
	* 'keywordRelations.keyword'. Property keywordRelations would give access to 
	* an array of objects of type KeywordRelation and property KeywordRelation>>keyword
	* would give access to one object of type Keyword.
	* @param String $path from a peanut whose property is described by $this
	* to the m to n related objects.
	*	(two steps, like the result of "$1ToNpropertyName.$nTo1propertyName")
	*/
	function setDerivationPath($value) {
		$this->derivationPath = $value;
	}