id	definition
01	Beginning Activity
02	Ending Activity
03	Activity
04	Interface Activity (when 2 or more separate networks are combined to create 1 network)
05	Summary Activity
06	Milestone
07	Event
08	Constraint - Finish to Start
09	Constraint - Start to Finish
10	Constraint - Finish to Finish
11	Constraint - Start to Start
12	Constraint - Dummy
20	Cost Account Activity
21	Work Package Activity
22	Data Item
PI	Maintenance Period Identifier
PM	Proposed Maintenance Action
SM	Scheduled Maintenance Action
ZZ	Mutually Defined