Difference among WBS, OBS, RBS and RAM


RBS or Risk Breakdown Structure

RBS is an hierarchical representation of risks, starting from higher levels and going down to finer level risks. This is similar to the organization of the Work Breakdown Structure (WBS). For instance, at the top level you could split your risk into technical risk, management risk, scheduling risk and external risks (Level 1), then go on to finer levels such as design risks, funding risk etc (Level 2) and so on. You can keep subdividing the risks into deeper levels as long it makes sense.

OBS or Organization Breakdown Structure

Organization Breakdown Structure or OBS is a hierarchical model describing the established organizational framework for project planning, resource management, time and expense tracking, cost allocation, revenue/profit reporting, and work management.



WBS or Work Breakdown Structure

Work Breakdown Structure or WBS is a key project deliverable that organizes the team’s work into manageable sections. The Project Management Body of Knowledge (PMBOK) defines the work breakdown structure as a “deliverable oriented hierarchical decomposition of the work to be executed by the project team.

RBS or Resource Breakdown Structure

In project management, the resource breakdown structure (RBS) is a hierarchical list of resources related by function and resource type that is used to facilitate planning and controlling of project work.


resource breakdown structure 2

RAM or Responsibility Assignment Matrix

RAM or a Responsibility Assignment Matrix, otherwise known as an RACI matrix, is an incredibly useful tool which project managers can use to accurately track the various roles and responsibilities of their team. RACI is an acronym of Responsible, Accountable, Consulted and Informed.





This identifies those who do the work to achieve the desired outcome in a task. There is always at least one person in a project deemed as Responsible, although others can be delegated to assist that role. The word ‘approver’ could also be used in this context, as this describes the person who will ultimately approve the completion of a task, as delivered by the Responsible. Often the people in this category are experts on a particular subject whose knowledge in that area is sought in order to improve the outcome of a project. This describes those who are kept up to date with a project’s progress and with which there is only a one-way communication. Informed roles do not have any input during the progress of a project.
Raci Matrix

Information from PMI,,,

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