LeanCPM vs CPM
CPM is a network of activities and relationships where some of the metadata is calculated using given algorithms.
The good
CPM is highly parametric. If a task is delayed, we can immediately see the downstream and second-order effects.
If done correctly, you’ll always know exactly which tasks need to be worked on on any given day, and which tasks can take a back seat.
The bad
CPM is complex, especially for superintendents who spend most of their day in the field and not in front of a PC. It’s why Scheduling Consultants are the highest-paid professionals in the industry.
Some superintendents want control over their plan, or simply don’t have the resources for a professional scheduler and will manage their schedules independently.
Most of the time, they spin their wheels to get nowhere. The rest can create a plan, but it’s almost always riddled with logic busts or poor quality issues, exposing the project to litigation.
The ugly
The Gantt chart UI encourages planners to create poor quality schedules, promotes working in a silo, and outright confuses everyone.
What are the high-level differences?
The main flaw we try to fix with legacy CPM is the why.
LeanCPM is designed for individuals who work in the field and lack the time to learn the theory and science behind a flawed system.
1. Relationships
Relationships are the links between activities. Legacy CPM has four types of relationships: FS, SS, FF, and SF.
LeanCPM has dependencies instead of relationships, and there are only two types:
- Series: A blocker must finish before the blocked task can start; lag is not allowed
- Parallel: A start-start and finish-finish relationship with an optional lag
2. Constraints
Tasks do not have constraints. A constraint in legacy CPM is a hard date, usually fixed by an outside force, that constrains tasks. The why is often missing, and it’s impossible to track changes.
In LeanCPM, instead of arbitrarily constraining a task, we introduce a new concept called Issues. Issues are similar to tasks, but with a few key differences.
- They don’t always have a start date
- Anyone can create them (but must be accepted by a planner)
A milestone can also be used as a constraint.
3. Milestones
In LeanCPM, all milestones have Target dates, which are used to calculate early and late dates.
Milestones must be in series with their dependencies.
4. No Data Date or schedule button
Two relics from the past where schedulers used to travel to jobsites and then several days later return to their computer to update the schedule.
Since LeanCPM is intended to be used by the boots on the ground synchronously, there is no need for this.
5. Priority instead of Total Float
Total Float is used to make sure no one finishes early.
LeanCPM uses total float, among other factors, to calculate priority.
Drag, the opposite of float, refers to the number of days by which moving the task’s target finish date earlier would also advance its milestone by the same amount.
6. Target Dates
LeanCPM allows the planner to set target dates within the early and late dates for any given task with a valid dependency path
7. Soft logic
This is our definition of constraints: a set of tasks that cannot be worked on simultaneously. It’s up to the planner to determine which happens first, based on their preference for sorting.