Introduction to Software Reliability
Software Reliability is an essential validation performed to determine the characteristics of a software system in terms of quality assurance, functional compatibility, applicability, overall efficiency, system performance, maintainability, system competence, installation coverage, and process documentation continuance. It is known to be a hard-hitting exertion, and the reason is the intricacy of the software systems is inclined to be elevated as the technological world’s growth is exponential over the years. For any given system, it takes a lot of work to achieve a convincing level of reliability, and the system engineers are going beyond the expected technical edges in order to achieve an up-to-date software application.
Software Reliability Metrics
The Software Reliability metrics are used to measure and derive the reliability of the software system application in the form of numerical or any type of mass expression. The type of metric chosen by the application developers can be reliant on the system behavior, the business purpose of the software, expected recovery time, possibility of failure, types of users that access the software, etc. The below are the commonly used types of evaluations in real-time, by the software application development professionals, to estimate the software reliability,
Based on Requirements
The software development specification documentation is used to discover the actual Requirements from the client standpoint. Typically, it describes the expectation and needs for creating the software, including functional attributes, non -functional appearance, and dependencies/ dependability for the software from other related systems. It is used to identify the functionality, which is obligatory for the software to behold in it.
It is used to cover the non –functional areas like the appearance of the software, performance validation, compatibility, integrating ability, load passed through the software in real-time, etc. The result of this process should show that there are no discrepancies observed involving the software development team’s understanding and the client’s needs.
Based on Design and Code
In the Design and coding stages, the evaluation for the software reliability is performed on the action plan. The areas on which the estimation is applied are the size of the software, the usability aspects, and the component of the software. It is important to keep the system in smaller units so that the possibility for mishaps is reduced in a highly remarkable way. When the fault occurrences are contained, then the reliability scale will perform as required for the analysis. Instead of having one big complex system, it is a good practice to have multiple components with understandable and easily operable units of the software.
Testing Reliability Metrics
During the testing phase, the reliability metrics used are made up of two different segments. One is the validation for matching the developed application’s functional behavior with that of the requirements specifications mentioned in the documentation. And, the other segment is to evaluate the program functions and its performance. The first one is considered to be a black box testing process, and the later is known to be a white box testing typically performed by the developer.
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The testing process is carried out against the already placed documentations, in the name of requirement specifications from the client. So, any mismatch in this stage will be reported and handled as the part of the bug fix and tracked in the form of a defect life cycle. It is used to achieve an effective way of validating the entire system and to make sure that every nook and corner of the developed system is validated.
The below are the methods used, based on the required type of metric analysis, during the above-mentioned software development phases,
- Mean Time to Failure – (Total time) / (Number of units tested)
- Mean Time to Repair – (Total time for maintenance) / (total repairs)
- Mean Time Between Failure – MTTF + MTTR
- Rate of Occurrence of Failure – 1 / (MTTF)
- Probability of Failure – (Number of Failures) / (Total cases considered)
- Availability – MTTF / MTBF
Software Reliability Techniques
Software Reliability is calculated with the help of two different techniques, such as,
- Prediction Modeling
- Estimation Modeling
1. Prediction Modeling
As the name says, the Prediction Model is built based on the assumptions that one has on the requirements provided for developing the given software application. These assumptions include the data and contents from the historic events or functional behaviors of the software. It is performed during the design phase, that is, before starting the development process, as it is considered to be highly unreliable to predict during or after development. Predictions are made keeping in contemplation that the application is to be used in some future period, instead of considering the current circumstances.
2. Estimation Modeling
Estimation Model is built based on multiple aspects of the software, and it used the current data outcome obtained during the development or the testing processes. It is performed at the later point of time in the software development life cycle when all the required software aspects are in hand. The Estimation applied to the reliability of the software is done based on the current or immediately following time periods. A few other models designed by various software development analysts are Basic Execution Time Model, Shooman Model, The Bug Seeding Model, Logarithmic Poisson Time Model, Jelinski, and Moranda Model, Littlewood –Verrall Model, Goel –Okumoto Model and Musa –Okumoto Model.
Example to Implement Software Reliability
Let us consider the calculation of Mean Time to Failure, where the Total time& the number of units tested are required.
For Instance, if the values are as below, the MTTF is calculated as,
MTTF = (total time) / (number of units tested)
= 100 / 40
= 2.5
Advantages of Software Reliability
The advantages of implementing Software Reliability as a part of Software Development process are
- Software Reliability is used for data preservation.
- It helps to avoid software failure.
- Straightforward in the system upgrade process.
- System Efficiency & higher Performance gives greater productivity.
Conclusion
Software Reliability validation is a vital step in the software development process, as it ensures the software quality & performance, functional fulfillment as stated as the prerequisites, effortless maintenance activities, etc. Though it is a vigorous process, to be run against the software being developed, a sturdy step to achieve better quality is typically acceptable.
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