The basic types of task available are ASAP ('As Soon As Possible'), ALAP ('As Late As Possible'), and Fixed. (Although each Summary task will be designated by the software as ASAP, ALAP, or Fixed, for the purpose of this discussion we prefer to consider all summary tasks as ASAP.) Usually, it is best to use as many ASAP tasks as possible to allow Time Line to automatically reschedule them as plans change or get recycled. Use Fixed tasks sparingly for setting the project start date or the start of a series of ASAP tasks, or the end date of a series of ALAP tasks. Other tasks that might need to be Fixed are tasks with solidly-known plan dates, such as meetings, contracted delivery dates, or other 'externally controlled' dates (like trade shows, flight reservations, and so forth).
ASAP tasks are the most commonly used task, and are the easiest to understand. ALAP tasks are used when a project end date or product delivery date must be met, and tasks that lead up to the last task are then scheduled as close to the end date as possible, but happening as late as possible and pushing predecessor tasks backwards to earlier dates. (An example of this kind of end date might be the departure date of an airplane an ALAP tasks going backwards in time in this instance might be 'Board Airplane', 'Pick up Ticket', 'Arrive at Airport', and so forth.) ALAP scheduling can be riskier than ASAP scheduling, because all ALAP tasks are critical, and a delay in any ALAP task will probably cause a delay in the end date or delivery date. (In the above instance, you would miss the plane!)
The earliest possible date that any task in the schedule can start is determined by whatever the Schedule Start Date is set to. The software considers other conditions to determine exactly when it will reschedule ASAP, ALAP, and sometimes fixed tasks, which we explain below.
In the sample schedule 'Business Schedule', all tasks are ASAP tasks, and are 'swept by' the As-Of Date. (This is the red vertical line that appears in the Task Bar Area, at the date specified by 'As-Of Date' in Options, Calculations.) In other words, the earliest date that the program will normally schedule any ASAP task will be the As-Of Date. However, if the 'Slip Tasks to 'Slip Tasks to As-Of Date Line' option in Options, Calculations is turned off, the earliest date that any ASAP task will be scheduled is the Schedule Start Date. The Schedule Start Date can be set in Options, Schedule. Generally speaking, if your tasks start as scheduled, or if you are entering historical data (adding tasks that have already been started or are already done), leave the 'Slip Tasks' option turned off to allow each task's Start Date to be scheduled immediately after its predecessor.
It is possible to assign a fixed date to a task by putting the mouse pointer on the middle of the bar and dragging it left or right. Note that dragging the task bar will convert ASAP and ALAP tasks into Fixed Start tasks, just as if you manually entered a date into one of their date fields.
It would be typical for a project manager to enter a date into the Start Date field for the task 'Research Development', once the actual start date of the series of tasks has been determined or committed to. This way, all tasks in the series of tasks that follow 'Research Development' can automatically be rescheduled by Time Line to appropriate dates, since they have been connected together with dependencies. To enter a fixed date into a task, either enter it directly into the appropriate column, or enter it into the Task Info or Timing Info box.
For beginners: When tasks are 'connected together', they are not necessarily going to occur one immediately right after the other. Connections to predecessor tasks only control the soonest an ASAP successor task can occur. (Conversely, connections to successor tasks only control the latest an ALAP predecessor task can occur.) Other factors may cause ASAP tasks to be scheduled even later than their connection(s) would, or ALAP tasks to be scheduled even sooner than their connection(s) would. For example, although we said (above) that Task C (Paint House) has to happen before Task D (Sell House) can happen, Task D (Sell House) could still be delayed by any number of other factors, such as 'Accept Offer'.