Overview of Key Terms

CPM Method – Critical Path Method (CPM) scheduling is a mathematically based scheduling technique used for scheduling an interdependent set of activities to complete a project.  A critical path is determined by identifying the longest path of dependent activities and measuring the time required to complete those activities from start to finish.  The CPM method requires that all activities (typically categorized within a work breakdown structure – WBS), activity durations (time), constraints (end points such as milestones or deliverables), and relationships or “logic” between activities are defined. The “Critical” path is the only path that extends from start to finish of the project – with no room for delay.  Every other path is considered “Non Critical” and have “Float” which can be delayed without making the project longer.

Activity or Task – A discrete scheduled component of work.

Data Date – The “as-of” date of the schedule.

Calendar – The sequencing of days for which an activity can be performed. (e.g. 5-day work week, 6-day, etc.)

Logic Types

• Finish-to-Start (FS): A tie denoting that a Successor can start after its Predecessor is Complete (e.g. Land must be purchased before road building can start). The Predecessor must finish before Successor can start.
• Start-to-Start (SS): A tie denoting that a Successor can start after its Predecessor has started (e.g. Road excavating must start before asphalt can be laid). The Predecessor must start before the Successor can start but the Successor can finish before or after the Predecessor.
• Finish-to-Finish (FF): A tie denoting that a Successor can finish after its Predecessor is finished. (e.g. Lying asphalt must be complete before line painting can be completed). The Predecessor must finish before the Successor can finish.
• Start-to-Finish (SF): A tie denoting that a Successor can finish after its Predecessor has started. (e.g. Road excavating must start before line painting can be completed). The Predecessor must start before the Successor can finish.

Planned Duration – The total number of working days estimated to complete an activity or task.

Milestone – A significant event in the project schedule, such as an event restraining future work

Constraint – A schedule constraint is a limitation that affects the start or end date of an activity. Schedule constraints can take the form of fixed imposed dates for a work item. Wide use of constraints is discouraged.

WBS Structure - Work Breakdown Structure - A work breakdown structure (WBS) is the hierarchical organization of the project activities into manageable scopes of work.  The Project Management Institute’s (PMI) Project Management Body of Knowledge (PMBOK) defines the work breakdown structure as a "deliverable oriented hierarchical decomposition of the work to be executed by the project team."  The work breakdown structure defines the scope into manageable chunks that a project team can understand, as each level of the work breakdown structure provides further definition and detail.  Starting with WBS Level 1 as the most summarized level, each subsequent WBS Level further breaks down the scope of work into more detail.

• Level 1 WBS – Most Summarized / Least Detailed
• Levels 2 through Level X – More Detailed Activities based on the scope of work to be performed

Float - or slack is the amount of time that a task in a project network can be delayed without causing a delay to: subsequent tasks ("free float"), or project completion date ("total float").  The total float represents the schedule flexibility.  Total Float (finish date) and Free Float (tasks).

Lag (Positive / Negative) – Lag: an additional time component that can be assigned to a relationship (e.g. a relationship with a Finish-to-Start relationship with a 2 day lag means that the Successor starts 2 days after the finish of the Predecessor.) Lag can be positive or negative.

Critical Path Delay – Critical Path Delay represents the amount of time in days the activities on the longest path have been delayed (e.g. delay impacting the project end date).  SmartPM’sTM Schedule Delay section indicates the total delay, future recovery, and end date variance from the Baseline to the latest update on the Project.

Recovery – Recovery represents the amount of time in days an activity or schedule has progressed better than planned.

End Date Variance - The difference between a scheduled end date and another scheduled end date. Typically measured in days from the Baseline schedule to the most recent or current updated schedule.

Compression – SmartPM’sTM Schedule Compression captures the amount of effort remaining in the schedule as compared to the baseline. This is an indicator of the effort required to meet the scheduled completion date. 

• A schedule compression value of 1.0 or 0% represents a non-compressed schedule
• A schedule compression value > 1.0 or > 0% represents a compressed schedule
• A schedule compression value < 1.0 or < 0% represents a decompressed schedule

Forecasted Completion - SmartPM’s™ Forecasted Completion date uses a proprietary AI based algorithm utilizing current progress to give an estimate of what the completion date of the schedule should be given things progress as they have thus far. The scheduled completion date shows the estimated completion date based on the current schedule update, delays to date, recovery, and schedule compression.