Dependency Management

Let's talk Dependencies. A Dependency is a relationship between two activities, and is most often encountered in the Project Schedule. In this case they are used to structure the order of tasks, to help you plan the Project. Logically, there are four type of Dependency relationship - shown in the diagram below:

1. F-S: Finish to Start - When the first task finishes the second can begin. This is the most frequently encountered type of Dependency, and the one we would assume for most tasks in day to day life - when when task finishes the next can begin. For example I must finish putting my shoe on before I can travel to work.
2. S - S: Start to Start - When the 1st task starts, it will trigger the second task to start. When I leave the house to walk to work I will switch on my music for the journey. You tend to encounter this when multiple activities are waiting for something to start before they can start.
3. F -F: Finish to Finish - When task 1 finishes it will trigger task 2 to finish. When the bar closes the music will be stop playing.
4. S - F: Start to Finish - When task 1 starts then task 2 finishes. Best to avoid this one as it can be a bit confusing. We tend to arrange tasks in roughly chronological order, but this has task 2 finishing first. When the delayed football match finally kicks off, the pre-match bar will close.

Lag and Lead time in also a concept in these logical relationship. Lag represents a time delay following task 1 before task 2 initiates, such as waiting for paint to try before fitting the wall lights. Lead is essentially negative lag, for example you could start fitting wall lights on one wall before all of the other walls paint has dried.

We've seen people make the mistake of thinking that by logging Dependencies in the logic of the schedule, that's them covered. But the problem with this is that a big schedule may have thousands of tasks and thousands of dependencies - how do you "see the wood for the trees"? You tend to find that, although there are many Dependencies on a Project, there are only a few key Dependencies. It's not worth making a special effort to track pretty mundane day-to-day dependencies which we take for granted, but these key Dependencies are critical to your Project's success - and so warrant special attention.

You can think of these key Dependencies in terms of a "Give-Get" relationship; either you are Giving or you are Getting. Typically it will be a key delivery from a 3rd party or supplier, or a key milestone date you have to deliver something to the client. In this case you should use a Dependencies Log to track them; this will make sure you maintain visibility of them and are able to more easily monitor them. An alternative is to recognise Dependencies as a source of Risk on your Project, which they certainly are; any "Gets" which you are waiting for from outside of the Project are not under your direct control. So you may chose to scan Dependencies to identify Risks that you need to log and manage, or you may actually integrate your Dependency Management into your Risk Management Tool/Process entirely.

What experiences do you manage Dependencies on your Project? And if you need a Project Dependency Log Template we have you covered in our template store!

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