A work breakdown structure (WBS) in project management and systems engineering, is a instrument used to define and group a project's distinct work elements (or tasks) in a way that helps organize and identify the total work range of the project.

A work breakdown structure element may be a product, data, a service, or any combination. A WBS also provides the essential framework for detailed cost estimating and control along with providing direction for schedule improvement and control. Furthermore the WBS is a dynamic tool and can be revised and updated as needed by the project manager.

The S Curve is a well known project management tool and it consists in "a display of cumulative costs, labor hours or other quantities plotted against time”. The name comes from the S-like shape of the curve, flatter at the start and end and steeper in the middle, because this is the way most of the projects look like.

The S curve can be considered as a display and it's used for many applications associated to project management such as: target, baseline, cost, time etc. That's why there is a variety of S Curves such as:
-Cost versus Time S Curve; (appropriate for projects that contain labor and non-labor tasks).
-Target S Curve ;( This S Curve reflects the ultimate progress of the project if all tasks are completed as currently scheduled)
-Value and Percentage S Curves ;( Percentage S Curves are useful for scheming the project's actual percentage complete)
-Actual S Curve ;( This S Curve reflects the definite progress of the project to date)

In order to be able to generate an S Curve, A Baseline and Production Schedule are necessary because they hold essential information for each task: -the Baseline - contains information concerning Actual Start date and finish date.
-The Baseline - can also contain information about Man Hours and costs.
-The Production Schedule contains information about the actual percentage complete.

There is some software scheduling packages that generate automatically S Curves. For example MS Project does not have this possibility so a third party software application is needed to process the Baseline and Production Schedule data and generate the needed S Curve.( for example S Curve Generator that integrates with MS Excel to generate S Curves).