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Linking Tasks and Dependencies

How to link tasks in ProjectLibre using the Critical Path Method, the four dependency types, and lag and lead.

ProjectLibre uses the Critical Path Methodology (CPM) to calculate your schedule. Linking tasks ensures that if a predecessor’s timeline shifts, the successor’s dates adjust automatically.

To test the structure and discipline of that CPM model, use Project Audit (DCMA Schedule Quality Audit).

Three Ways to Link Tasks

Gantt Chart Drag-and-Drop: Click and hold a predecessor task bar, then drag the connector line to the successor task bar.
The Predecessor Column: Type the ID number of the predecessor directly into the “Predecessor” column in the spreadsheet. For multiple links, use a semicolon (e.g., 3;4).
Network Diagram: Click and drag between task nodes (boxes) to create a logic flow.

Relationship Types & Offsets

Click on any link line (the arrow) to edit the relationship type. The Edit Task Dependency dialog offers FS / FF / SS / SF plus Lag (Days) — for example Start-to-Start with a 2-day lag (SS+2d), as shown in the 2.0 preview.

Code	Type	Meaning
FS	Finish-to-Start	(Default) Successor starts when predecessor finishes.
SS	Start-to-Start	Successor starts when predecessor starts.
FF	Finish-to-Finish	Successor finishes when predecessor finishes.
SF	Start-to-Finish	Successor finishes when predecessor starts (Rare).

Using Lag and Lead

Two ways to offset a link: lag and lead:

Lag (Positive): FS+2d adds a 2-day delay after the predecessor finishes.
Lead (Negative): FS-1d allows the successor to start 1 day before the predecessor finishes.

Example: Project Precedence Logic

The following table shows how data in the Predecessor column builds a logical sequence:

ID	Task Name	Predecessor	Relationship Logic
1	Project Summary	N/A	Automatically rolls up subtask data.
2	Design	—	The project start point.
3	Development	2	Starts after Design finishes (FS).
4	Document	2	Runs in parallel with Development.
5	Test	3;4	Starts only when both Dev and Doc are complete.
6	Product Rollout	5	Final Milestone after successful testing.

Spreadsheet with the Predecessor column filled in (2, 2, 3;4, 5) and the linked Gantt bars for Design, Development, Document, Test, and Product Rollout

Network Diagram with Design linking to Development and Document, both linking to Test, then to the Product Rollout milestone

Dependencies set the logic network. Next, assign people (Assigning Resources), then use Scheduling for baselines, calendars, constraints, task types, and tracking — before Resource Leveling resolves overallocation.