Skip to main content

Dependencies & Constraints

In a professional schedule, tasks rarely exist in isolation. The relationship between tasks—how one affects the start or finish of another—is what defines the project's critical path.

Tasks and Links

Task Dependencies​

MSP Planner supports the four standard industry dependency types, allowing you to model complex project logic:

1. Finish-to-Start (FS) - The Standard​

The most common link. Task B cannot start until Task A is finished. Example: You cannot start "Testing" until "Development" is complete.

2. Start-to-Start (SS)​

Task B cannot start until Task A has started. Example: "Documentation" can start as soon as "Development" starts.

3. Finish-to-Finish (FF)​

Task B cannot finish until Task A is finished. Example: "User Acceptance Testing" cannot finish until "Bug Fixing" is finished.

4. Start-to-Finish (SF)​

Task B cannot finish until Task A has started. (Rarely used, typically for shift-handover scenarios).

Lead and Lag: Fine-Tuning the Schedule​

In real-world projects, dependencies are rarely perfectly flush. MSP Planner supports Lead and Lag to model these nuances:

  • Lag (Positive Value): Adds a mandatory delay between tasks. For example, a "Finish-to-Start + 2 days" link can model a waiting period, such as allowing concrete to dry before starting the next phase.
  • Lead (Negative Value): Creates an overlap between tasks. A "Finish-to-Start - 3 days" link allows Task B to start slightly before Task A finishes, which is common for overlapping phases like "Development" and "QA Testing."

By applying lead and lag, you avoid "over-optimistic" schedules and ensure that your critical path reflects real-world constraints rather than just theoretical links.

Managing Dependencies in the Workspace​

You can create dependencies using two high-efficiency methods:

  • The Toolbar: Select two tasks and click the Link button in the top menu.
  • The Gantt Chart: Click and drag the end of one task bar to the beginning of another to create a visual link.

To remove a dependency, select the linked tasks and click the Break button in the toolbar, or right-click the dependency line in the Gantt view and select "Delete."

Handling Constraints​

Beyond simple links, you can apply constraints to tasks to force specific behavior. In Auto-Scheduling mode, MSP Planner uses these constraints to ensure your manual date placements "stick" during recalculation.

  • Must Start On (SNET): The task cannot start before a specific date, regardless of its dependencies. This is often automatically set when you drag a bar's start edge.
  • Must Finish By (FNLT): The task has a hard deadline that must be respected. This is often automatically set when you drag a bar's finish edge.
  • As Soon As Possible (ASAP): The task will move as far left as its dependencies allow.

These constraints allow you to maintain a deterministic schedule while still having the flexibility to manually anchor specific tasks to key dates.

The Impact on the Schedule​

When you link tasks, MSP Planner's scheduling engine automatically recalculates the dates for all downstream tasks. If a critical task is delayed by two days, every dependent task will shift automatically, providing you with an instant, updated project finish date.

This automation is what allows you to perform "What-if" analysis: you can move a task to see how it impacts the overall project deadline without manually updating every subsequent date.