How does PISO work?
The PISO method is represented by a framework of stages and steps, as shown in the diagram on the right. As Data Flow Diagrams (dfds) are the core analysis technique, the steps that use dfds have been highlighted. It can be seen, however, that there is more to PISO that the use of dfds. In particular, note the parallel activities in stage 1.
As explained earlier, in PISO, the "employee stakeholders" are actively involved with the development to the point where many of them are expected to not only be conversant with, but actively engaged in, the techniques that the method uses.
The act of handing over the analysis techniques in this way empowers these stakeholders. This motivates them to work together to come up with agreed operational objectives, and finally a workable solution. And because everyone has worked together to agree the outcome, there tend to be few of the common "people" problems in implementing it.
The key to PISO's successful use of dfds is the way it introduces a new twist to the process of dfd logicalisation. It begins conventionally enough - stripping away all the physical constraints represented by a "current system" dfd in order to gain an efficient view of what a system is achieving, and an insight into the policy behind it.
Within conventional structured systems analysis, this new logical dfd would be completed by simply considering add-ons or changed facilities that had been requested, and creating a diagram that incorporated these. Instead, PISO demands that an agreed strategic objective to improve the business in some way, meet a need, solve a problem, is carefully defined before this second logicalisation is embarked upon.
Instead of assuming that the aim is to create a computer system that will efficiently carry out the current way of going on (perhaps with a few juicy extras), PISO gives the opportunity to ask not only "is the current way the right way?" but "are we fundamentally doing the right thing?" - and the re-engineered solution may or may not include changes to computer facilities, or recommendations for completely new ones, as part of the solution.
It uses the knowledge and creativity of the employee stakeholders to first determine operational objectives in line with the strategic objective, then think of these in terms of "dfd objectives", and then use these to re-engineer the first logicalised dfd in order to create a new one. Finally, as with conventional systems analysis, a "new physical" dfd is created (step 3.3 in the diagram) that represents a model for physical implementation - but with PISO it now encapsulates the strategic objective.
Those who would like to read more about the method will find a full description of PISO in "An Introduction to Systems Analysis Techniques (Second Edition)", Lejk and Deeks, Addison-Wesley, 2002. The book includes a full explanation as to how the Pontefract transformation came about, as well as other case study material.
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