Background - Using Event-B for Critical Device Software Systems - page 26

and accurate requirements of any medical system for designing and manufacturing
a safe system. The CDRH allows premarket review to identify relevant informa-
tion for processing, manufacturing, assembly handling, maintenance and disposal
of the system. Moreover, the CDRH also seeks to determine if the manufacturer
has captured the important aspects of the development life-cycle for producing a
product [ 59 , 66 ]. However, the CDRH is also concerned with potential users like
patient or clinician, who will use the device. FDA requires product performance to
be verified [ 59 , 60 , 66 ] and validated [ 59 , 66 ]. The FDA supports the performance
and safety assessment of a system through providing the evidence that the system
is adequate to use in practice. The FDA regulatory oversight of the manufacturing
process through the Quality System Regulation [ 59 , 66 ].
Increasing complexity and safety recalls in the medical systems advocate a new
approach for a good design for reliability (DFR) in the medical industries [ 42 ].
DFR describes the tools and techniques that can support product and process design
to ensure the system reliability. The DFR is a process that spans the entire product
development cycle from concept to release of a product. The DFR [ 42 ] indicates the
following paradigms that are essential to design a complex medical system:
1. Spend significant effort on requirement analysis
2. Critical failure is not an option for medical devices
3. Measure reliability in terms of total Life-cycle cost
4. Don't just design for reliability, design for durability
5. Design for prognostics to minimise surprise failures
2.8 Safety Standards
It is perhaps best to start by considering the various standards that exist for indus-
tries, which develop the safety critical systems. Standards are documented agree-
ments containing technical specifications, which produce precise criteria, consistent
rules, procedures to ensure reliability, software processes, methods, products, ser-
vices and use of products, are fit for their purpose in this world. Standards include a
set of issues corresponding to the product functionality and compatibility, facilitate
interoperability including designing, developing, enhancing, and maintaining. A set
of protocols and guidelines, which are produced by the standards, are consistent and
universally acceptable for the product development. The standards allow to under-
stand the quality of different products for competing with them, and provide a way
to verify the credibility of a new product [ 22 , 54 , 58 ].
Verification and validation (V & V) are part of the certification process for any
critical system. There are several reasons, why certification is required for any crit-
ical system. For example, medical device like a cardiac pacemaker must obtain a
certificate before to use in practices. Certification of the product not only assures
about the safety, but also helps to a customer to gain confidence to buy and to use
the product, which is also important for commercial reasons like having a sales
advantage to industry. Certifications are usually carried out by some national and