User's Guide to  

RiskyProject Professional

Predecessors and Lags

Information about predecessors and lags can be defined in the Predecessor tab of Task Information dialog box.

You can use the Standard toolbar button to link tasks; however, this method of creating task dependencies has limitations:

• You cannot link a task (from example Task #5) to a previous task (for example Task #3).
• You cannot input lag, which is time delay between predecessor and successor. RiskyProject allows you to setup probabilistic lag with statistical distribution defined by low, base, high number.

Tip: 

Sometimes it is convenient to use predecessor tab instead of link toolbar buttons when task has multiple predecessor or if there is a big difference in task Ids between current task and predecessor. For example, it is not convenient to link task number 5 to task number 74 using toolbar buttons.

To add a predecessor to a task:

1. Select the task to which you want to add a predecessor.

2. Open the Task Information dialog box. See the About Task Start Time, Finish Time, and Duration topic to read more about opening the Task Information    dialog box.

3. Click the Predecessor tab.

4. On the first row of the grid, click in the Task Name cell. A drop-down list appears containing a list of all available tasks or type 

5. Select the predecessor from the drop-down list
    Or
    Type in the id number associated with the predecessor in the ID column. By default, the predecessor type is Finish- Start (FS).

6. If required, enter a lag time. Use the Lag low and Lag high cells to enter a range of time. Lag can be positive or negative

7. If you are entering a base, high and low lag, you can change the default distribution using the drop-down list in the distribution cell.

• If the low and high lags are different, the default distribution is triangular. 
• If low, base, and high lag are the same, the distribution is undefined.

8. If required, edit the Seed number. Seed is the starting parameter used for the random number generation that is used to calculate lag. If you have two predecessors, and they have strong positive correlations between their lags, you can make their seeds the same. For example: low lag for one predecessor will coincide with low lag for another predecessor. 

9. Click OK

Notes:

• You can make a task be a predecessor to itself
• You cannot create a schedule that it will lead to a circular relationship between tasks
• You cannot link a summary task to one of its subtasks
• You cannot link two tasks twice.