The Schedule – Dependency Chain

"Things derive their being and nature by mutual dependence and are nothing in themselves.”

                                                                                                              - Nagarjuna

In my previous post on scheduling basics, I listed the essential requirements to have a well-formed schedule, which is also the sequence for developing them:

• WBS
• Dependency chain
• Task effort estimates
• Resource assignments
• Resource leveling
• Risk buffers

This post will discuss the Dependency Chain.  The dependency chain obviously sequences the tasks in the order that you plan to perform them.  A well-formed schedule, though, adds some best practices to the typical attributes. 

A true dependency relationship between two tasks is when a work product output of one task is necessary to start or complete a second task.  When that condition is true, there is a dependency from the second task on the first task.  What this excludes are artificial or convenience “dependencies” to accommodate resource availability, resource leveling, or the PM’s view of “reality.”

Assuming you are using a decent scheduling tool, the tool has features to effectively address resource availability (calendars) and resource leveling.  Thus, if you use dependency chains instead of the appropriate features, you are diminishing the effectiveness of the tool to support your scheduling efforts and you are introducing complexities when conditions change (as they always change) and you have to reschedule.  To restate that:  if you follow the best practice, then you maximize the effectiveness of the scheduling tool and enhance your flexibility to respond to changing conditions.

As you will see over the next few posts, we will continue to build on the foundation of the WBS, now with the dependency chain, to develop the well-formed schedule.

Do you agree that task dependencies should be based on work products (including deliverables)?  Is there ever an occasion to base a dependency on anything else?

The Schedule - Basics

Success is neither magical nor mysterious. Success is the natural consequence of consistently applying the basic fundamentals.

                                                                                                - Jim Rohn

On completing my recent series on the Work Breakdown Structure (WBS), I promised to continue the series on project management fundamentals with The Schedule.   In this post, I’ll discuss the basics of a well-formed schedule, to be followed in future posts with advanced scheduling techniques and best practices.

A schedule is more than just a timeline.  Most “schedules” that I see are actually timelines.  That is, they are a graphic representation of what the PM wants the schedule to look like, how the PM wants the project to flow.  A well-formed schedule, in contrast, is how the PM plans for the project to flow based on a given level of certainty (probability).  It is for this reason that a (time) schedule (and equally a cost schedule) can only be done integrally with appropriate risk management.

A well-formed schedule is built in these steps and, if any steps are omitted, it is not a well-formed schedule and therefore is not reliable:

• WBS
• Dependency chain
• Task effort estimates
• Resource assignments
• Resource leveling
• Risk buffers

We’ve already talked about the WBS.  Over the next few posts, I will expand on these other necessary elements of the schedule.  In addition, there is an optional step to quantify the reliability of the schedule.  This topic is challenging to explain and probably requires a full book to do it justice, but I will at least address the high-points.

One final thing before I close this post:  If you follow these steps and develop a well-formed schedule, will that guarantee a good schedule?  The short answer is: No.  Ignoring the obvious path that “good” is subjective and the pitfalls that leads to, my point is that following the “process” or steps of producing a schedule does not compensate for experience or fate.  That is, if an experienced PM produces a timeline without resource leveling, they will not have a reliable schedule.  On the other hand, if an inexperienced PM follows all of these steps, they still may not have a reliable schedule.   There are lots of ways to produce an unreliable schedule.  And sometimes God just laughs.

Other references on scheduling:
                PMBoK v4, chapter 6 (Project Time Management)
                The Practice Standard for Scheduling v2

The WBS - Intermediate

Two (or six) months into your project, you and your business owner disagree about whether a particular feature or component is included in the project.  You, of course, consider this controversial item obscure and expensive to include;  the business owner, in contrast, asserts that it is absolutely essential, the whole project is value-less without this item, and, further, that since it is in the original scope it shouldn’t cost more or take more time.  How do you resolve this dilemma?

Project Management success is determined by delivering both the project (what you promised) and customer/owner/stakeholder satisfaction (what they expected).  Failure at either of these is failure.  Even if you deliver the greatest technical solution imaginable, if the customer is not happy, you are not going to stay around long or get that next job.

Our success as project managers, then, is to get agreement up front for what we’re going to do, do it, and then get acceptance that we did it.  How then do we get agreement on scope up front?  How do we avoid the dilemma described in the opening paragraph?

The Work Breakdown Structure, which I’ve been discussing in the past several posts, is not an academic exercise.  It, along with the Task Dictionary, defines the scope of your project.  A well constructed WBS/ Task Dictionary agreed to at the start of the project by the key stakeholders will greatly reduce the kind of disagreements described above.  That is, the WBS becomes the basis for determining Project Change Management, and without the WBS it is just “I say – They say,” which ultimately leads to project failure.

Agreement on the WBS is more than just sending an email and asking for approval.  Sit down with your stakeholders, walk through each Deliverable and The Activities and The Tasks that comprise each deliverable.  Discuss what is included.  You’ll be amazed at the results.  Many misunderstandings will be cleared up here, early enough to easily resolve them and prevent acrimony later;  they will find that you’ve included activities that they disagree with;  they will identify missing activities;  and, most importantly, they will begin to take ownership of the mutual delivery of the project.

I’ll have more to say about Project Change Management in a future post, but the other essential value of the WBS is that it becomes the foundation for building the project schedule.  In the next series of posts, we’ll discuss what is needed to build a well-formed project schedule.

When was the last time you conducted a WBS walkthrough with your stakeholders?  How did it turn out?

The Activity

In my previous post, The WBS Basics, we developed a simple Work Breakdown Structure (WBS).  In previous posts related to this foundations series, I’ve discussed TheTask and Deliverables.  A WBS is, as previously noted, a hierarchical representation of the complete project scope.  (A list of all tasks without any organization structure would be more confusing that beneficial.)

But with a moment of consideration about the hierarchical nature of this representation, we realize that if we just have tasks at the bottom and deliverables at the top, we really haven’t improved the situation meaningfully.  With no hierarchy, a Deliverable with hundreds of tasks would be just as confusing as a project with hundreds of tasks.

Therefore, it’s easy to determine that for large projects, there could be several layers between the Deliverable and the Task, as represented by this diagram with arbitrary names for the intermediate levels.

A work breakdown structure is like an assembly Bill of Materials – it lists all of the components in the final product and shows graphically how they fit together from individual parts (Tasks), through subassemblies (Activities), to the top level assemblies (Deliverables).  And the WBS developed for project management much like the Bill of Materials developed for assembly and they serve much the same purpose.  Complex BoMs with randomly arranged layers are normal.  Likewise, there is nothing wrong with (defective about) a WBS like this and I’ve certainly seen many PMs comfortable with this (un)structure.

 

As already mentioned, large projects have many (thousands of) tasks and the hierarchical structure is needed to organize the work.  The intuitive choice for organizing the work, as a box is examined and decomposed, is to build the structure into progressively more levels, as shown above.  This is evident to most practitioners and quite obvious.

But this blog is for presenting Best Practices and I’m going to explain why an alternative, not necessarily as intuitive, is the Best Practice.  Let’s say you have a project template that you use that has four deliverables and usually takes a couple of months.  Thus, you produce a deliverable every couple of weeks.  Then you get a request for a really BIG version of this same project that will take two years.  The intuitive approach, as discussed, would be to build out detail within each box (for assemblies, what they would call exploding the BoM).  You would then have your familiar project structure with possibly several additional levels.

But do you really want to have only four deliverables over a two year period?  Do you want to “go dark” for six months at a time?  This is not a Best Practice.  All projects need frequent deliverables to get meaningful feedback on the quality of the work.  Consultancy PMs in particular benefit from frequent deliverables so that they can book the revenue.

As more deliverables are added to the WBS, it naturally flattens out so that a PM only needs a limited number of levels.  Gone are the Assemblies, Subassemblies, and Hemi-Demi-Semi-assemblies.  You can even deduce that a WBS with many layers would be a red flag to review the frequency and distribution of the deliverables.

I have run many large projects with only three hierarchies within the project:  Deliverable, Activity, and Task.  Further, unlike the example above that appears to have evolved randomly, a planned, well-structured WBS is the sign of an organized project.

Have you run a project where you didn’t have control over the WBS?  How did it turn out?

The WBS Basics

In the WBS, use nouns for deliverables and work packages;  use verbs to name tasks.

-          Danu M. Kothari, Managing Successful IT Projects with the basic “Tools of the Trade,” PMI ISSIG Webinar, July 20, 2006

I have talked about TheTask and Deliverables.  We now have the background to drill into the Work Breakdown Structure (WBS).  The WBS is a “deliverable- oriented hierarchical decomposition of the work to be executed by the project team to accomplish the project objectives and create the required deliverables.  It organizes and defines the total scope of the project.”  (PMBoK v4, p452).  Other than being a circular definition, this is consistent with what I said in “Deliverables as Revenue Agents.”  The stars of this definition are “hierarchical” and “deliverables.”   “Decomposition” and “scope” are supporting cast members.

Since Deliverables define the total scope, the structure starts like this:

Project WBS Example

·         Deliverable 1

·         Deliverable 2

·         Deliverable 3

We now have a decomposition of the total scope for a three deliverable project.  Is this a WBS?  No, the work (each Deliverable) has to be decomposed to the lowest level of work.  As I described in The Task, that level of decomposition is the task.  A well-formed task has one owner and one work product.  We can now show our example project structure as:

Project WBS Example

·         Deliverable 1

o   D1 Task 1

o   D1 Task 2

·         Deliverable 2

o   D2 Task 1

·         Deliverable 3

o   D3 Task 1

o   D3 Task n

This, in fact, is a simple well-formed WBS.  It has a hierarchical structure, is decomposed to the individual task, all tasks are contained within deliverables, and the deliverables (and tasks) define the total project scope.

In my next post, we’ll build on this foundation to explore variations on the basic WBS structure.

Are you ready for more advanced WBS concepts?