Dependency Management: Different Types of Dependencies you Need to Manage

Dependency Management is at the heart of project planning and scheduling. However, much of the discussion on the topic focuses on the technical aspects, such as different type of task relationships. What is not discussed is the different categories of dependencies themselves. Read on to discover the different types of tasks relationships you need to manage, the different ways that you can link relationships and how different stakeholders influence and constrain your freedom to act. 

by Bryan Barrow

Definition of a dependency

A dependency is a relationship between activities or tasks, where the latter task cannot be completed without something from the former. Most writing on the nature of dependencies describes three types of dependencies, these are:

  • Logical dependencies, where a task or activity cannot take place without the start or finish of its predecessor;
  • Preference dependencies, where there are two or more options for the order in which a set of tasks can be completed. The actual ordering of the tasks is left to the person or team responsible to decide;
  • Resource dependencies, where the duration of a task may be reduced through the addition of extra resources or effort.

Although these are all accurate, as you’ll soon see, there’s more to the subject of Dependency Management than this. First though, let’s take a closer look at logical dependencies. From now on I’m going to use the term task relationships to distinguish between the linking of tasks and other aspects of dependencies.

Task relationships

Task relationships describe the ways that any two tasks may be connected and there are four ways to link any two tasks together:

  1. Finish-to-Start Relationships
  2. Start-to-Start Relationships
  3. Finish-to-Finish
  4. Start-to-Finish Relationships.

Finish-to-Start Relationships

The first type of relationship is the finish-to-start (FS) relationship, where the start date of Task B is dependent on the finish date of Task A. It will probably represent more than 90% of the relationships in your project.

A Finish-to-Start (FS) relationship

Start-to-Start Relationships

The second type of relationship is the start-to-start (SS) relationship, where the start date of Task B is dependent on the start date of Task A. This is common where several activities are all dependent on a common trigger.

A Start-to-Start (SS) relationship

Finish-to-Finish Relationships

The third type of relationship is the finish-to-finish (FF) relationship, where the two tasks may start at different times, but the finish date of Task B is dependent on the finish date of Task A.

A Finish-to-Finish (FF) relationship

Start-to-Finish Relationships

The final type of relationship is the start-to-finish (SF) relationship. With this relationship the finish date of Task B is dependent on the start date of Task A. Although this type of relationship isn’t used often there are circumstances where the start-to-finish relationship is appropriate, for example, where you want to switch over from one activity to another without a break in service.

A Finish-to-Start (FS) relationship

Simple and complicated task relationships

One thing that is often overlooked when discussing task relationships is that the examples above are the simplest form of relationships. There are many circumstances where there are several tasks that are related.

Task relationships can range from simple to complicated, and the more complicated the task relationship, the more likely you are to suffer setbacks if you don’t act. Although most of your project tasks can be described using simple finish-to-start relationships as shown above, there will be some instances where you have more complicated relationships to manage, especially with people and groups outside your project. Here are five ways that your tasks may be linked together, ranging from simple to complicated:

  1. The Handover
  2. The Exchange
  3. The Interdependency
  4. The Bottleneck
  5. The Delivery

The Handover

The first and most straightforward type of task relationship, where Task A is connected to Task B. If Task A is late, then this can have a knock-on effect on Task B and all subsequent work.

The Exchange

An exchange takes place where two parties exchange something between them at the same time. For example, if you order materials from a supplier which are to be paid for on delivery, you make the payment at the same time as your supplier hands over the delivery.

The Interdependency

This is where a third party supplies something to you, which you use to create something you later supply back to them. Any delay to either activity, either by you or your third party, may result in project slippage.

The Bottleneck

A bottleneck exists where several people or groups are dependent on the completion of the same predecessor task. A delay to the predecessor affects multiple other parties at the same time. If any of your project tasks are likely to affect several people or groups, then you are a potential bottleneck for them.

The Delivery

This type of relationship is more complex than the bottleneck. In this scenario you’re waiting on several prerequisites to be satisfied before you can get started. Each prerequisite may come from a different provider and run along different timelines, none of which are under your control. This is what makes it so difficult to manage, and so easy to be impacted.

Different types of dependency

We’ve said earlier that resource dependencies can affect the completion of tasks. What isn’t discussed is a much more important topic, the nature of the resources that you need to secure and manage. There are seven types of dependencies that you need to manage to deliver your project. These are:

  1. Tasks, the logical sequencing of project activities. We’ve already talked about different types of task relationships above;
  2. People: you need people to do project work on your behalf. Many of these people will not work directly for you, so you must secure their time;
  3. Assets: these are things that you need to do work that are limited in availability, controlled centrally, or supplied to you by others. Examples of assets include ingredients and materials, meeting- and training rooms, capital equipment, and artefacts created by others that you need as inputs to whatever work you are doing;
  4. Funding: money is a resource for projects just as it is for businesses, and making sure that you have the funding that you need at the right time can make or break your project just as it can bankrupt a business;
  5. Support: This includes both backing by key stakeholders at significant points in your project, as well as day-to-day actions and decisions that colleagues and collaborators take that can slow you down, even unintentionally (that you need to manage as inbound or outbound dependencies);
  6. Time: You probably don’t see time as a resource, but what you overlook is that your chances of successfully delivering your projects are strongly correlated with the amount of time you are given to complete them. A key part of setting up your project for success is managing expectations, in particular about how long your project will take;
  7. Team: You need create the conditions that bring people together on your project, so that they help, support, and sometimes carry each other. Think of your project as a relay race: everyone has their individual role to play, but the key determinant of success is how well team members collaborate.

The impact of dependency management on stakeholder relationships

This raises the question of whether tasks are internal to you project and / or internal to your company. Dependencies are internal to your project or external to your project, as shown below:

 

Outside – Inside Dependency Grid. Source: Girls Guide to PM

This view is based on tasks and their origin. Another way of looking at this is based on stakeholders and relationships. What is often overlooked in discussions about project dependencies is that project tasks must be completed by people and groups outside your team and a major cause of so many project problems is poor stakeholder management. 

Here’s why there is a link between your relationships with project stakeholders and your dependency management activities:

  • Projects leverage capabilities and utilise resources to deliver results that lead to benefits. You need to understand the expected results of your project and how they relate to the wider business benefits, so that you know how your project’s success will be measured along the way;
  • Your project will have several powerful stakeholders to satisfy. They have the power to stop your project if they choose, so you need to retain their support if you are to succeed. These stakeholder needs are often overlooked or under-appreciated, so you must invest enough time and effort to build relationships with these stakeholders;
  • Some of your stakeholders are internal to your organisation; these are people and groups with power and influence. Other stakeholders are outside your organisation; they are responsible for setting of laws, regulations, standards, policies, and guidelines that you must follow. As such, you are working to ensure and demonstrate compliance with these external standards, so that you project is not delayed;
  • Project activities are those that are within your ability to manage and control. However, you will be reliant on resources and subject to constraints that are outside your control. You need to negotiate for and secure these resources, so they are available when you need them. You must also be aware of any constraints that your project is affected by;
  • Your project is just one of many initiatives taking place at the same time. You need to be aware of other projects and activities that your project has a relationship with, so that you can work together and support each other;
  • Anything that is outside your ability to control is outside your scope and therefore is an external dependency. Some of these external dependencies are internal to the company (as seen in the Outside – Inside Dependency Grid), but others are with third parties, including vendors and sub-contractors. There will be steps involved in identifying, contracting with and working with these third parties that you need to plan for.

A Stakeholder-Dependency Matrix

When trying to understand your project and its environment you should think about your stakeholders, starting from the outside and work your way inwards. Here are some questions you should ask yourself:

  1. Why are you doing this project, and for whom?
  2. What external constraints and limits exist that will have a significant influence on your project’s approach and scope?
  3. Which other projects and initiatives are related to yours and what do you need from each other?
  4. What is it that your project needs to do and what resources do you need to achieve your objectives?
  5. How will your project’s success be measured?

Conclusion

Task relationships are a core part of project planning and control, but much of your success in executing projects comes down to cultivating relationships that allow you to secure legitimacy, resources and support. If you are to succeed in delivering your project you need to spend time thinking not just about how any two tasks may be linked, but also what resources you need, who you need to collaborate with and what external constraints your project may need to navigate. If you invest a small amount of your time managing dependencies and relationships, you will be rewarded several times over, in the form of supportive stakeholders, fewer delays and happier customers.

About Bryan

Bryan Barrow helps technology companies reduce project delivery costs by 10 – 20% while reducing risk of late delivery. Bryan is a business consultant and the author of several books on Project Management, including ‘Stakeholder Management’ and ‘The Project Planning Workshop Handbook’.

Picutre of the front cover of the book Dependency Management, by Bryan Barrow

Bryan’s latest book is for people who are struggling to deliver projects on time because they are not sure how to manage dependencies. It is due out in 2021. To join the list to be notified when the book launches, click here.