Work breakdown structure
The WBS ( PSP ) ( English structure break down work abbreviated WBS ) is the result of a subdivision of the project in plan and controllable elements. A project is divided into subtasks and work packages as part of the structuring. Sub-tasks are elements that have to be subdivided further, work packages are elements that are located in the PSP on the lowest level and are not further subdivided there. Work packages contain the elements ( process , processes) that are required for the further planning stages. According to the current state of knowledge of project management, the creation of a project structure plan is one of the central tasks of project planning. The PSP is the basis for scheduling and scheduling, resource planning and cost planning. In addition, the findings from the PSP are incorporated into risk management. Because it can be seen as the basic planning for a project, the PSP is often referred to as the “plan of plans”.
The most important design goal for a work breakdown structure is the complete and one-time recording of all relevant activities of a project. In order to achieve this goal, starting from the top level, the project itself, a uniform structure principle - orientation - is used for each level when creating the next level down . The orientations permitted according to DIN standards 69900 ff. Are:
- Function-oriented structure
- The function-oriented structure asks for the functional areas of the organization carrying out the project. The focus is on the type of activity to be performed.
- Object-oriented structure
- With the object-oriented structure, the focus is on the product itself. The project object is broken down into its individual components, assemblies or individual parts.
- Time-based structure
- For a time-oriented structure, one considers the process or the phases of the project. These then form the subtasks or work packages of the respective level.
The most widespread project management standard worldwide, the PMBoK Guide of the Project Management Institute, names these structuring options, as does the later developed ICB standard , which is used by the European IPMA , the German GPM and thus also the German Standards Committee.
Mixed forms of the orientation method are possible insofar as different levels can be created according to different orientations. In order to be able to achieve the design goal, however, it is recommended in practice to use only one orientation method for one level.
Three methods are established for creating work breakdown structures:
- Top-down approach
- The deductive path leads from the whole into detail, the PSP is formed by breaking down the project through to the work packages.
- Name of the project
- Selection of the appropriate orientation method for the second level
- Breakdown of the overall project into sub-projects or subtasks
- List of the tasks or structural elements of the second level
- Selection of the appropriate orientation method for each element of the second level
- Further dismantling until work packages are available
This procedure is often chosen if there is already experience with similar projects or the contents of the project to be planned are largely known.
- Bottom-up approach
- The inductive path leads from the detail to the whole, the PSP is formed by combining the activity through to the project.
- Collection of tasks to be carried out in the project
- Analysis of relationships with the question of what is part of what
- Structure and composition in a tree structure
- Control of completeness and uniqueness of all tasks
This procedure is suitable for projects with a high degree of innovation.
- Yo-yo procedure
- In the countercurrent process, deductive and inductive steps are carried out alternately in order to use the strengths of both processes. In order to use this method sensibly, however, it should not be used for a section of the project that is too small.
To ensure that no tasks are forgotten and no tasks occur more than once, the following rules should be observed:
- Uniqueness: The structural elements of a level must be completely different from one another in terms of content.
- Completeness: The total content of the elements that belong to a higher-level element must match the content of the higher-level element.
Achieving the design goal of completeness and uniqueness is promoted if attention is paid to approximately the same level of detail when creating the work packages.
The tree structure has proven itself and established itself in practice for displaying work breakdown structures . This can be created horizontally ( outline ) or vertically. A text structure is also possible, which shows the work breakdown structure with the help of outline levels and indentations. That is u. a. the case with IT tools like Microsoft Project . The most important representation goal is clarity. Project structure plans should be created and presented in such a way that a competent person can understand the object under consideration without any effort.
Advantages and Limits
The advantages that a work breakdown structure offers are immense. The “hard factors” are that the project is fully recorded with the PSP, there is clarity about the work to be performed, the cost situation has been approximated, the required resources are known, etc. But “soft factors” also play an important role . The penetration of the project brings clarification of questions and misunderstandings, agreement on project goals and the internalization of the project for those involved in the planning (project manager, project planner, core team).
One cannot speak of the disadvantages of a work breakdown structure, but of its limits. It is particularly noticeable with function and object orientation that the process concept for the project is almost neglected. However, this is not the intention for a PSP at all; such questions will only be clarified in later planning steps.
New construction of a garage
In the following example, the top level is time-oriented because the focus is on the process. The second level is function-oriented, as in this case the subcontractors are viewed as functional units. A vertical tree structure is used for the display.
The results of the project structure planning are used in the following planning steps:
- Scheduling and process planning : As a rule, the work packages of the PSP form the basis for processes that are used in network planning , in Gantt charts, in process lists or in similar tools.
- Resource planning : Based on the work packages, it can be determined which resources are required when (in combination with scheduling and scheduling).
- Cost planning : In combination with resource planning, costs and the time at which costs are incurred can be planned.
- Risk planning : The work packages can be used to gain knowledge of technical, personnel and operational risks that must be recorded in the risk register.
Standard work breakdown structures
Since projects are basically one-off or first-time projects, it can also be assumed for work breakdown structures that each PSP is unique. However, if you take certain industries or certain types of projects into account, you find that the content of plans is repeated. This is particularly evident in companies that process orders in project form (software industry, construction industry, plant engineering, etc.). Standard breakdown structures offer the possibility of saving considerable planning work, since such a plan only has to be adapted to the existing task. If a standard PSP is designed as the maximum solution, it can also be used as a checklist. This ensures that no essential tasks are forgotten.
- Franz Xaver Bea, Steffen Scheurer, Sabine Hesselmann: Project management. 2nd Edition. UTB, Konstanz 2011, ISBN 978-3-8252-2388-5 .
- Günter Drews, Norbert Hillebrand: Lexicon of project management methods. 2nd Edition. Haufe, Freiburg 2010, ISBN 978-3-448-10224-6 .
- Gerald Patzak, Günter Rattay: Project Management. 5th edition. Linde, Vienna 2009, ISBN 978-3-7143-0149-6 .
- Heinz Schelle: Leading projects to success. 6th edition. DTV, Munich 2007, ISBN 978-3-423-05888-9 .
- Manfred Schulte-Zurhausen : Organization. 5th edition. Vahlen, Munich 2010, ISBN 978-3-8006-3736-2 .
- See: Erhard Motzel: Projektmanagement-Lexikon. 2nd Edition. Wiley-Verlag, Weinheim 2010, pp. 194f.
- DIN-Taschenbuch 472. Beuth-Verlag, Berlin 2009.
- A Guide To The Project Management Body Of Knowledge. 6th edition. Project Management Institute, Pennsylvania (USA) 2017, pp. 195ff.
- See: Gerold Patzak, Günter Rattay: Projektmanagement. 5th edition. Linde, Vienna 2009, p. 223f.
- Heinz Schelle: Leading projects to success. 6th edition. Munich 2007, p. 19.