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.
In the building industry, this term is used for the information that allows you to understand a building and also the steps needed to keep both the building and the people who occupy it safe.
The golden thread will hold the information that those responsible for the building need to:
- Show that the building is compliant with applicable building regulations during its construction and provide evidence of meeting the requirements of the new building control route throughout the design and construction and refurbishment of a building.
- Identify, understand, manage and mitigate building safety risks in order to prevent or reduce the severity of the consequences of fire spread or structural collapse throughout the life cycle of a building
The information stored in the golden thread will be reviewed and managed so that the information retained, at all times, achieves these purposes.
The golden thread encompasses the information documents and the information management processes (or steps) used to support building safety. The golden thread information should be stored as structured digital information and managed, maintained and retained in line with the golden thread principles. The UK government will specify digital standards which will provide guidance on how these principles can be met.
The golden thread information management approach will apply through design, construction, occupation, refurbishment and ongoing management of buildings. It supports the wider changes in the regime to promote a culture of building safety. Building safety should be taken to include the fire and structural safety of a building and the safety of all the people in or in the vicinity of a building (including emergency responders).
Many people will need to access the golden thread to update and share information throughout a building’s lifecycle, including but not limited to building managers, architects, contractors and many others. Information from the golden thread will also need to be shared by the ‘Accountable Person’ with other relevant people including residents and emergency responders and will play a pivotal role in the safety case.
A Safety Case presents the argument (or claim) that a system is safe. The argument must be clearly structured and supported by evidence. An argument without evidence is unfounded and evidence without an argument is unexplained. A safety case is intended to justify that a system is acceptably safe in a specific operating environment. It provides a clear summary of the design and operating procedures required by the competent regulatory or operating body and allows them to make an informed decision on safety. It must provide the external viewer with the logical reasoning as to why a building or a change to the structure and operating procedures of that building is safe. Absolute safety is an unobtainable goal and the safety case is there to convince someone that the building is safe enough to be occupied . Context free safety is impossible to argue, almost any building can be unsafe if used inappropriately. It is the job of the Safety Case to define the context within which safety for the building is detailed.
A safety case is a comprehensive and structured set of safety documentation such as safety arguments and organization, safety analysis, compliance with the standards and best practice, acceptance tests, audits, inspections , feedback and safe use such as emergency procedures. Documentation should be prepared in sufficient detail so that anyone reading it will be able to see not only what decisions were reached but what the justification was for classifying risks as tolerable and acceptable. This is where the golden thread aligns with the safety case, providing the latest, up-to-date and relevant documents as ‘evidence’ in the safety case .
Regulators are increasingly requiring safety cases as a means to demonstrate that the required, tolerable levels of safety have been achieved and legislative & regulatory requirements met, as is now the case in the building industry.
Safety cases often amount to hundreds of thousands of pages and are compiled with input from many organizations and a myriad of information tools and sources. In this environment, relevant information can take a long time to find and the lack of explicit links to data means that information supporting arguments are duplicated in many places, leading to errors in amendment and update.
Although it is possible to communicate safety arguments clearly with text, unless very tightly and painstakingly controlled, its flexibility can allow unclear, ambiguous and misleading arguments to be expressed. It can be extremely difficult to clearly present complex interrelationships and cross-references, with text. This point has long been appreciated in most engineering disciplines, where engineering drawings and design notations are typically used to describe artefacts of any significant structural complexity.
The DSM uses Goal Structuring Notation (GSN) for the presentation of safety arguments. It is an internationally recognized graphical notation – explicitly representing the individual elements of any safety argument (requirements, claims, evidence and context) and (perhaps more significantly) the relationships that exist between these elements (i.e. how individual requirements are supported by specific claims, how claims are supported by evidence and the assumed context that is defined for the argument).