System Hierarchy and Breakdown Structures

By: Alex MillerSES 405

March 19th, 2013

● Two types of organizational structures:

○ Product Breakdown Structure (PBS)

○ Work Breakdown Structure (WBS)

● Creating a system hierarchy to manage the breakdown structure

● A look at JWSTs breakdown structure

Concepts Covered In This Module

Definition of 'Product Breakdown Structure' (PBS) According to The

Module

[On Next Slide]

Exploration Systems Engineering: Hierarchy Module

Creating a Product Breakdown Structure is a way of visually organizing all of the physical 'pieces' of an engineering project. It allows the project to be easily split up between large groups of people as well as providing an excellent framework for how all pieces of the system interact with each other.

My Definition of PBS

● The Module's Definition:

Hierarchy/Hierarchical Levels: The relationship of one item of hardware/software with respect to items above and below in the relative order of things.

To Create A Breakdown Structure, You Need Hierarchy!

● Organizes project work● Contains every possible physical and

intangible component of the design● 'Top-down' structure with the lowest-level

being the 'products'

Purpose and Benefit of The Hierarchy

Exploration Systems Engineering: Hierarchy Module

● Creates an in-depth visual model for how the systems will be operated and designed○ Helpful for creating design requirements ○ Assists with traceability

● Complex engineering designs can be tackled piece-by-piece○ Allows allocation of labor to very specific areas

The Pros of Breaking A Product Down

● Reveals unexpected interfacing needs between certain components of the design

● Forces the engineers to consider how system resources will be distributed

● Engineers responsible for certain hierarchal systems must come up with performance requirements

(These are the types of things that we have been struggling with in class but are essential for the design to work)

The Cons (Which Are Actually More 'Pros' In Disguise!)

I. Similarities to PBS:a. Based off of the PBSb. Lowest levels of the chart are still the end products

II. Differences from PBS:a. Includes required work, management, services, ect.

that it takes to design each component in the hierarchyi. Uses project life cycle for timelinesii. Good for developing budget estimatesiii. Dictates how components will be documented

[WBS visuals on next two slides...]---->

Work Breakdown Structure (WBS) [Similarities and Differences to PBS]

Exploration Systems Engineering: Hierarchy Module

Exploration Systems Engineering: Hierarchy Module

● In the following slides I've included some snippets of the important sections of JWST's WBS

● In this particular document, the authors opted for an outline and descriptive approach instead of using a block diagram

JWST Work Breakdown Structure

Backup Slides

Key Definitions [Next Two Slides...]

Common WBS Errors [Next Three Slides...]

Exploration Systems Engineering: Hierarchy Module

Exploration Systems Engineering: Hierarchy Module

Exploration Systems Engineering: Hierarchy Module