Out of Sequence Conditions

“. . . and you will respect my authoritah!”

- Eric Cartman, South Park

What is an out of sequence condition?

In this check, DCMA is looking for out of sequence tasks and milestones. An out of sequence condition exists between a predecessor and successor when there are forecast or actual dates that violate the relationship type. DCMA considers all incomplete predecessor tasks and milestones in the schedule.

Let’s use a finish-to-start (FS) relationship as an example. Suppose that Task A is an incomplete FS predecessor to Task B. If Task B has a forecasted or actual start that is before Task A’s forecasted finish, it is out of sequence. Consider this relationship where we’re saying that Task B cannot start before Task A finishes. The schedule shows that Task B is scheduled to start (or has begun) before Task A is forecasted to finish.

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Why are out of sequence conditions an issue?

Presumably, the relationship exists for a good reason. The schedule, in its current state, has a plan that disrespects that relationship. At the very least, breaking the relationship bears some attention.

What other out of sequence conditions exist?

If any of the other three relationship types (FF, SS, and SF) are violated, an out of sequence condition exists. For example, if a start-to-start (SS) relationship exists and the successor’s forecast or actual start is before the predecessor’s forecast start, we are out of sequence.

Won’t leads cause out of sequence conditions?

They will. A lead is essentially a negative lag. While a lag introduces a fixed delay between a predecessor and successor, a lead is an overlap. In a finish-to-start relationship, for example, if the successor begins two days before the predecessor is forecast to finish, there is a lead of two days. DCMA counts out of sequence conditions caused by leads as part of the results, and in those cases, they will determine whether there is adequate justification for the lead.

Next steps

It’s not possible to “undo” an out of sequence condition because you can’t “unstart” a task. However, it would be prudent to discover why the out of sequence conditions are happening. For each out of sequence successor, investigate by checking with the person responsible for the start of the successor. Some things to consider:

  • Is there a breakdown in communication? Sometimes collaboration issues can be the cause of out of sequence conditions.

  • Are there parties who are trying to cut corners by starting early?

  • If the reason for the relationship is legitimate, what are the consequences of Task B starting out of sequence? 

  • If there are no consequences for the task being out of sequence, are there other relationships in the schedule that aren’t necessary? Can they be removed to simplify the schedule?

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