Question:  What are predecessors in Scheduling? What is a critical path? How do you use them?


Using predecessors maximizes schedule efficiency by setting the subtask order so each task may begin as soon as possible or progress in the ideal order.

When you set a task as a predecessor, you are creating a critical path relationship between two tasks. A predecessor will indicate that Task 2 needs to begin a certain number of days before or after Task 1 is completed. Using predecessors creates a critical path, which is a string of dependent tasks. If the start date is moved for a task in the critical path, you will be able to see what tasks are affected and how your completion date is affected.

UDA Scheduling offers multiple tools for defining and analyzing predecessor and critical path relationships, including Autoset Predecessor, Lag Time, Show the Predecessor Tree, Show Critical Path, and Show Duplicate Tasks.

Set a predecessor

1.   Determine which subtask needs to be complete for a second subtask to begin.  You will set a predecessor for the second subtask. For example, you might set a predecessor of Electrical Labor for Electrical Rough-In Inspection. 

2.   To create a predecessor, click the predecessor cell for the second subtask.

3.   In the predecessor dialog box, enter the number in the ID column for the first (preceding) subtask.

4.   In the predecessor dialog box, click Advanced to schedule a Lag Time. A lag time schedules the subtask to start a specified number of work days before or after its predecessorís end date. Select a positive number of days to schedule a subtask to start after its predecessorís end date, or a negative number of days to schedule a subtask to start before its predecessorís end date.

5.   Click OK.

6.   UDA Scheduling will set the start date for the second subtask as the next work day after its predecessor is completed, or according to the lag time you specified.

For more information on predecessors, see Scheduling.