Defining the Project Boundaries

At an early stage in the project planning it is necessary to carefully define the scope of the system or module under examination. Limiting and articulating the scope is necessary to define the boundaries that have been applied to the analysis. More importantly, this formalises those system entities which have not been subject to analysis. The safety case will therefore say nothing about the clinical risk associated with those components outside of that defined boundary. By instituting boundaries early on in a project one is able to more accurately size the target and define the resources and timescales necessary to complete the task. 

Beyond defining the product and configuration often the easiest place to start setting a boundary is with the logical system architecture. For example, the system may be modular with weU-demarcated interfaces to other components. In this case, it is reasonable to apply a boundary around the module and either include or exclude the relevant interfaces. On the other hand, it is quite possible that a module is only ever deployed in conjunction with other modules and therefore this level of granularity may be inappropriate. 

One should also consider the physical architectural components of the system. Would it be appropriate to undertake separate safety analyses on the processing, storage and network components of the system For example, suppose a hospital 

For some systems, a geographical approach may be taken in defining scope. For example, one may need to consider the safety impact of a hospital s servers being destroyed in a fire or natural disaster. It would be sensible in this case to draw boundaries around those systems which are hosted together or have similar dependencies. 

A key purpose of the safety case and the associated hazard log is to formally communicate those controls which other stakeholders are required to implement. In many cases, this translates into a natural boundary between the supplier of a HIT system and the healthcare organisation who implements it. Safety cases frequently demarcate the scope at this convenient level and also make it possible for the parties developing safety cases to mirror the commercial contract. 

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