code: public static Constraint modificationConstraint(String modifTerm)
  	{
  		return new FieldOfMultiple(new MappedConst(new LinkedPE(LinkedPE.Type.TO_SPECIFIC), 0),
  			"PhysicalEntity/feature:ModificationFeature/modificationType/term",
  			Field.Operation.INTERSECT, modifTerm);
  	}
docs: Makes sure that the PhysicalEntity or any linked PE contains the modification term. Size = 1.
  @param modifTerm term to check
  @return constraint to filter out PhysicalEntity not associated to a modification term