In Section 8 of “Building a Safer Future” the UK government describes the need for a “golden thread” of safety information which will be maintained throughout the life of a large residential building. It describes the challenges of out-of-date information as:
- It is unclear whether any changes have been made between original design and the completion of construction which may have an impact on the building safety strategy.
- The building owner does not have the required up-to-date information to be able to easily and effectively manage building safety across its life cycle.
- When refurbishing a building, it will be difficult to ascertain what effects any changes may have on building safety.
However it is not enough merely to update the building plans or other documentation: the impact on the safety case must be considered too.
This is where a structured argument, especially in a notation like GSN, comes into its own. GSN links arguments to evidence, so the impact assessment is simply a matter of checking any changes to the evidence against the arguments that it currently supports. If this happens because of differences between plans and as-built then the impact is simple to assess, and if necessary a revised safety argument can be produced which uses new arguments and evidence. If this happens when planning a refurbishment then the relevant low-level safety goals can be added to the specifications.
This table provides a cross-referenced list of each “goal” (i.e. a component of the safety argument) that the building documentation must meet. So for instance any change to the building signs must maintain the prohibition of storing things in the stairwells. This table is generated automatically from the structured safety argument, so it is guaranteed to be updated along with the argument.
Without this table any change to the building will depend on some combination of personal knowledge and an exhaustive review of every aspect of the safety case. With this table the review becomes trivial; look up the modified documents in the table, and read off the relevant safety goals.