Why Your Schedule’s Logic Matters More Than Its Dates
Ask most people what a Primavera P6 schedule *is*, and they’ll describe a Gantt chart, a wall of bars stretched across a calendar. That’s a fair mental picture, but it’s also a little misleading. The Gantt chart is the schedule’s face and what it shows depends entirely on what’s happening underneath.
Underneath every Gantt chart is a Network Diagram. A web of activities connected by relationships that determine, mathematically, when everything can happen. Change one relationship and dates cascade across the whole project. Get the relationships wrong and the schedule might still *look* fine while quietly telling you the wrong story.
That’s why the relationship types you choose, not the bars you see, are the real measure of a schedule’s quality. This is why the DCMA 14-Point Assessment cares so much about how activities are linked.
This ebook is a field guide to that layer of P6 scheduling.
What’s Inside
The Network Diagram opens the collection because everything else depends on it. Before relationship types mean anything, you need a clear picture of what a network diagram actually is.
Finish-to-Start (FS) Relationships covers the workhorse of the four relationship types, the one where a successor can’t begin until its predecessor finishes. It’s the most intuitive logic there is, it drives the Critical Path Method, and it’s the easiest for stakeholders to read at a glance.
Start-to-Start (SS) Relationships introduces the tool schedulers reach for when work needs to overlap rather than run strictly in sequence. SS lets a successor begin as soon as its predecessor begins, which is powerful for compressing a schedule.
Finish-to-Finish (FF) Relationships flips the focus from starts to endings. FF is the tool for coordinating a shared finish line. This chapter shows how FF constrains the back end of two activities and why getting a coordinated finish right is often harder than getting a coordinated start right.
Start-to-Finish (SF) Relationships rounds out the set with the relationship type almost nobody uses and explains why that’s usually the right call. This chapter is as much about recognizing when *not* to use SF as it is about the mechanics when you do.
How to Read This
You don’t need to read these in order, but there’s a logic to the sequence. Start with the Network Diagram to ground the vocabulary, then move through FS, SS, FF and SF as a progression from “use this by default” to “use this only when you have a very specific reason.”
Each chapter includes worked examples of the forward and backward pass, so you can see exactly how early dates, late dates and float get calculated under each relationship type. Not just what the relationship means, but what it *does* to your numbers.
The theme across all five chapters is the same idea. Transparency isn’t a nice-to-have in a schedule, it’s a quality metric!
