Discuss Quality and reliability  in Software Engineering and the relationship between Quality and Reliability

Answer:

Quality is the standard of something as measured against other things of a similar kind; the degree of excellence of something.

In software development, quality of design encompasses requirements, specifications, and the design of the system. Quality of conformance is an issue focused primarily on implementation. If the implementation follows the design and the resulting system meets its requirements and performance goals, conformance quality is high.

Quality control involves the series of inspections, reviews, and tests used throughout the software process to ensure each work product meets the requirements placed upon it. Quality control includes a feedback loop to the process that created the work product. The combination of measurement and feedback allows us to tune the process when the work products created fail to meet their specifications. This approach views quality control as part of the manufacturing process. 

Quality control activities may be fully automated, entirely manual, or a combination of automated tools and human interaction. A key concept of quality control is that all work products have defined measurable specifications to which we may compare the output of each process.

But a product is of high quality does not always mean it is highly reliable as well. 

We can measure reliability of a product in terms of whether it is sustainable, durable, safe to use, etc. Now it is expected that a good quality product will have such characteristics. A product X may be built with high design quality and high features but built to last only for a year without errors. So if we have to discuss reliability in long durability, it is not reliable after a year.

Statistically the software reliability may be defined as the probability of an operation of a computer program which is free from error or has not failed during the operation time, tested under a specified environment and for specified time. 

Failure refers to non conformance to the requirements of the software stated. 

One of the simple measures of reliability is the express it as the meantime between failure (MBF) which is the sum of mean time of occurrence of failure (MTF) and mean time towards repair (MTR). It is necessary to identify and assess the hazards in software projects that affect the software performance. If it is possible to identify the hazards in the early stages of the software project then a module to counteract such hazards could be developed or built in to the software which will then be able to rectify errors leading to hazards. Suitable models could be used to achieve this safety.