The Product Flow Diagram is a very powerful feature of Product Based Planning. Though this diagram looks similar to Precedence Diagrams or Network Diagrams, the information that is represented is very different. For those familiar with the Capability Maturity Model Integration (CMMI), this diagram provides the core of the Product Integration (PI) Process Area though a lot wider.
My understanding of the PFD is that the focus is on 'Product Completion' order. For a product to be complete, the capabilities defined in the composition section must be complete and a quality check has been performed to demonstrate this. This means that if a product is dependent upon another product, the dependent product must be complete. In this context, the concept of an 'Integration Product' is also very important, for example, the quality check for an integration product is roughly similar to integration testing of the set of completed products. The quality check for an Integration Product might be the integration tests for the set of products.
In some project management approaches, the product flow diagram links are referred to as 'Hard Dependencies' based upon the physical nature of the product. 'Soft Dependencies' on the other hand tend to relate to resource availability and allocation as one example. If there are a number of products that can be done in parallel and in no particular order, resource allocation tends to be the major scheduling constraint. Soft dependencies tend to be handled using project management tools that do resource planning (MS Project). These tools can also show hard dependencies too.
Understanding the nature of the links on a PFD can help reduce the number of links on a diagram and help clarify the purpose of many products. For example, any products further down the flow from a product can rely on all previous products having been completed and approved. In the case of an integration product, the full collection of products that have been integrated can be considered complete. So a link from an integration product is a link from any of the completed products making up the integration product.
These concepts are also important when attempting to roll-up these links into a higher view of the product flow. I have attached a Product Based Plan PBP file to demonstrate some of these concepts. I'll provide some annotated pictures in some replys to this topic. The example includes integration products, one potentially redundant flow and an example of how common components can be shared across multiple flows. NOTE: this also has implications on the PBS.
FlowPatterns001.zip- Flow patterns and roll-up.
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I have also seen a few excellent examples of a PFD for complex multi-stage projects ... I hope the structure / patterns will be shared in this topic too..
Please share your thoughts and experiences using Product Flow Diagrams and any patterns that you may have found!! Feel free to comment on the above too!!
Regards, Bruce