A Critical path is the sequence of project network terminal elements with the longest overall duration , determining the shortest time to complete the project.
The duration of the critical path determines the duration of the entire project. Any delay of a terminal element on the critical path directly impacts the planned project completion date (i.e. there is no slack on the critical path ).
A project can have several, parallel critical paths. An additional parallel path through the network with the total durations just shorter than the critical path is called a sub-critical path.
The critical path method was invented by the DuPont corporation and originally considered only logical dependencies among terminal elements
Application of Theory of Constraints (TOC) to Project Management
TOC Presented in his Business Novel The Goal
CCPM Presented in his Business Novel Critical Chain
TOC suggests that all real-world systems have at least one constraint; otherwise they would be capable of infinite throughput, which is clearly impossible.
TOC claims that a real-world system with more than three constraints is extremely unlikely.
Managing a complex system can be made simpler & effective, by providing managers with a few specific focus areas on which to focus -- maximizing performance in the areas of key constraints, or "elevating" the constraint
A System’s Optimum Performance IS NOT the Sum of Local Optima
A System Has Only One Constraint at a Time
Constraints Can Never Really be Eliminated
Can Move From One Part of the System to Another
In project management, the critical chain is the sequence of both precedence- and resource-dependent terminal elements that prevents a project from being completed in a shorter time, given finite resources.
If resource availability is not a constraint, then a project's critical chain is identical to its critical path.