SYSTEM RELIABILITY SPECIFICATION Software reliability
Software quality
In the context of software engineering, software quality refers to two related but distinct notions that exist wherever quality is defined in a business context...
What is software reliability?
Software Reliability is the probability of failure-free software operation for a specified period of time in a specified environment. Software Reliability is also an important factor affecting system reliability.
What are reliability requirements?
Reliability requirements are typically part of a technical specifications document. They can be requirements that a company sets for its product and its own engineers or what it reports as its reliability to its customers. They can also be requirements set for suppliers or subcontractors.
What is Software Reliability Program Plan (SRP)?
“Software Reliability Program Plan” tailored based on the risk level of the particular software release. Defines which Software Reliability Engineering (SRE) tasks are implemented for this program i.e. failure mode analysis, predictions, sensitivity analysis, etc.
What is the reliability performance of a component?
The reliability performance will be uncertain. Generally, suppliers desire to provide components that last longer than the products expected duration of use. Suppliers do not want to field customer complaints that their element of a product is causing premature or early failures.
What is reliability specification?
The reliability specification must cover all aspects of the use environment to which the item will be exposed and which can influence the probability of failure. The specification should establish in standard terminology the “use” conditions under which the item must provide the required performances.
What is meant by software reliability?
Software reliability is the probability of failure-free operation of a computer program for a specified period in a specified environment. Reliability is a customer-oriented view of software quality. It relates to operation rather than design of the program, and hence it is dynamic rather than static.
What is software reliability and how it is measured?
Software reliability testing is a field of software-testing that relates to testing a software's ability to function, given environmental conditions, for a particular amount of time. Software reliability testing helps discover many problems in the software design and functionality.
What is the importance of software reliability?
Software Reliability is an important to attribute of software quality, together with functionality, usability, performance, serviceability, capability, installability, maintainability, and documentation. Software Reliability is hard to achieve, because the complexity of software tends to be high.
What are the 3 types of reliability?
Reliability refers to the consistency of a measure. Psychologists consider three types of consistency: over time (test-retest reliability), across items (internal consistency), and across different researchers (inter-rater reliability).
What are the four types of reliability?
4 Types of reliability in researchTest-retest reliability. The test-retest reliability method in research involves giving a group of people the same test more than once over a set period of time. ... Parallel forms reliability. ... Inter-rater reliability. ... Internal consistency reliability.
How is reliability measured?
To measure interrater reliability, different researchers conduct the same measurement or observation on the same sample. Then you calculate the correlation between their different sets of results. If all the researchers give similar ratings, the test has high interrater reliability.
What are the types of reliability?
There are two types of reliability – internal and external reliability. Internal reliability assesses the consistency of results across items within a test. External reliability refers to the extent to which a measure varies from one use to another.
How can software reliability be improved?
3 Ways to Enhance Software Reliability and Increase Speed to MarketAgile Sets the Foundation. The Agile methodology and cross-functional teams deliver software faster and more reliably through an iterative approach to development. ... DevOps Builds Upon Agile. ... Cloud Provides the Environment.
What factors determine the reliability of software?
Factors Influencing Software ReliabilitySize and complexity of code.Characteristics of the development process used.Education, experience, and training of development personnel.Operational environment.
What is software reliability and availability?
Availability is a measure of the percentage of time that an IT service or component is in an operable state. Reliability, on the other hand, is a measure of the probability that the system will meet defined performance standards in performing its intended function during a specified interval.
What is meant by software reliability and availability?
Availability is a measure of the percentage of time that an IT service or component is in an operable state. Reliability, on the other hand, is a measure of the probability that the system will meet defined performance standards in performing its intended function during a specified interval.
What is the example of reliability?
The term reliability in psychological research refers to the consistency of a research study or measuring test. For example, if a person weighs themselves during the course of a day they would expect to see a similar reading. Scales which measured weight differently each time would be of little use.
What is software reliability and hardware reliability?
Software reliability tends to change continually during test periods. While hardware reliability may change during certain periods such as initial burn in or the end of useful life however it has a much greater tendency then software value.
What is software reliability modeling?
A software reliability model indicates the form of a random process that defines the behavior of software failures to time. Software reliability models have appeared as people try to understand the features of how and why software fails, and attempt to quantify software reliability.
What is software reliability?
As stated in opening, software reliability can be defined as the probability of failure-free operation of a computer program in a specified environment for a specified time. This definition is straightforward, but, when the reliability is expressed in this way, it is hard to interpret.
What is the main objective of a software reliability model?
The main objective of a software reliability model is to provide an opportunity to estimate software reliability, which means that Fig. 4 may be complemented as shown in Fig. 12.
Why is software reliability important in testing?
One of the primary goals of testing is to improve reliability, because reliability is a user-centric measure. This study attempts to gain some insight into the use of reliability assessment in GUI testing. Since the early seventies of the last century, several techniques have been developed to model and predict software reliability. Software reliability assessment techniques to be used differ according to the phase of software development process [4]. In testing phase, software reliability growth models (SRGMs) are used to predict reliability. Existing SRGMs attempt to statistically describe the software testing process and to determine or predict the reliability of the SUC. These techniques model the reliability based on particular assumptions or preconditions on probability distribution of cumulative number of failures, failure data observed, and form of the failure intensity function, etc. The most widely accepted of those models are collected and recommended in standards such as [5,6].
How many datasets are assessed in GSE?
GSE assessed two actual datasets using our formulated equations, which are related to three types of development uncertainties by employing simple approximations in GSRM. The results confirm that developments can be evaluated quantitatively. Additionally, a comparison of GSRM with existing software reliability models demonstrates that the approximation by GSRM is more precise than those by existing models [20].
How are SRGMs selected?
Some SRGMs are selected by comparing the properties of failure data and the assumptions of SRGMs.
Is software implementation less critical?
For non-critical and less critical types of applications, the software implementation process is, however, less constrained (as in the choice of language and tools that the processes use especially for verification and validation), which induces quality of any software, resulting in lower reliability of software, which can therefore induce behavior contrary to availability.
Can SRGMs be totally infeasible?
We expect that in GUI testing, methods and frameworks used may affect the shape of failure data. Some SRGMs may turn out to be totally infeasible. Therefore, SRGMs that demonstrate a better performance may vary with respect to the selected GUI testing framework. This work aims to gain some experimental insight in the use of SRGMs in GUI testing by discussing the following issues.
What is reliability statement?
The reliability statement may be as simple as a failure rate value, or a set of formulas describing the likely time to failure under specific stress. This latter example is very rare, unfortunately. Most reliability specifications are lacking one or more of the four elements of a fully stated reliability goal.
What is specific requirements?
Specific requirements for purchased elements of a product provide the supplier the necessary information to provide or craft an element of the product that enables the system to meet reliability goals. If the supplier does not know the reliability requirements, they will attempt to provide a part that meets the stated requirements only.
How long does it take for a component to be 99.9% reliable?
Instead of creating a component that is exactly 99% reliable over 5 years, the supplied part may actually achieve 99.9% reliability over 5 years.
When setting a reliability goal, what are the apportioned goals for purchased elements?
Just as when setting a reliability goal the apportioned goal for purchased elements require all four elements: Specific requirements for purchased elements of a product provide the supplier the necessary information to provide or craft an element of the product that enables the system to meet reliability goals.
How long does it take for a cell phone to be reliable?
If the cell phone has a system goal of 95% reliable over 5 years, then the main circuit board within the phone may have a reliability goal of 99% reliable over 5 years.
Can expectations and capabilities be communicated clearly?
This really only can occur if the two parties communication the expectations and capabilities clearly.
What is software reliability?
Software reliability is also defined as the probability that a software system fulfills its assigned task in a given environment for a predefined number of input cases, assuming that the hardware and the input are free of error.
Why is software reliability so hard to achieve?
Software Reliability is hard to achieve because the complexity of software turn to be high. While any system with a high degree of complexity, containing software, will be hard to reach a certain level of reliability, system developers tend to push complexity into the software layer, with the speedy growth of system size and ease ...
What is software reliability?
The goal of software reliability and maintainability is to assure that software performs consistently as desired when operating within specified conditions. Depending on the level of fault or failure tolerance needed, the software should operate safely or achieve a safe state in the face of errors.
What is reliability analysis?
Reliability analysis looks at the functionality of the software early and as the designs and development progress. The purpose is to help identify where potential weaknesses in the design may impact reliability. Typically, it includes reviewing error checklists for software safety or security to see if any known potential weaknesses are present. Analyses such as FMEA or FTA can also help find where additional fault tolerance or a change in design is needed.
What are the results of reliability planning activities?
The results of the reliability planning activities, including the system’s reliability level, the software target reliability level, the planned analyses, important metrics to be collected and/or analyzed, processes used for reliability, responding to hardware changes, issues, and communication, need to be documented in a software reliability plan (or a reliability section in the software assurance plan).
How to plan for a reliable software?
In order to plan the activities necessary for a reliable software, it is necessary to have a good understanding of the system and its reliability needs and what role software will have in supporting the system's reliability. It will be necessary to have a close working relationship with the system analysts and designers as the system develops in order to learn how the various functions will be designed and shared across hardware and software and what the reliability goals for these will be. The software goals will need to support the achievement of the system reliability goals. Different types of analyses need to be chosen and design features need to be chosen to monitor and respond to hardware faults and failures as well as other features in other areas that might negatively impact the reliability. And in order to be able to determine the attributes of reliability, metrics will need to be chosen and plans established for their collection and analysis.
Why do software goals need to be chosen?
Different types of analyses need to be chosen and design features need to be chosen to monitor and respond to hardware faults and failures as well as other features in other areas that might negatively impact the reliability.
What is good workmanship in software development?
Good workmanship means good SW development practices are established and followed. Those processes and practices need to find and remove defects from the SW products, changing the software development processes as needed to assure fewer error insertions. To assure good workmanship, using the defect analyses, the SA personnel track defects during development and determine the types of problems occurring, determine if they are systemic, and then work with SW Engineering on how to get rid of the source of error insertion. This may mean a process change, additional reviews, and even extra tests. Defects need to be detected, identified/typed, and recorded for additional analyses.
What are the areas of software assurance?
Software assurance personnel need to support the following areas within the development cycle to help the software people achieve greater software reliability: 1) Workmanship, 2) Software Requirements Analysis, 3) Software Design Analysis, and 4) Software Safety Analysis In order to perform these activities, the various reliability activities need to be planned so the appropriate activities can be performed during the right phases of development and so the basic information and resources needed will be available when needed. In order to properly plan the reliability activities, it is necessary to understand what each activity involves and how to apply the activities to the software being built.
What is reliability specification?
The reliability specification must cover all aspects of the use environment to which the item will be exposed and which can influence the probability of failure. The specification should establish in standard terminology the “use” conditions under which the item must provide the required performances.
What is reliability requirement?
a quantitative statement of the reliability requirement. a full description of the environment in which the equipment/system will be stored, transported, operated and maintained. the time measure or mission profile. a clear definition of what constitutes failure.
What is the first step in reliability engineering?
The first step in the reliability engineering process is to specify the required reliability that the equipment/system must be designed to achieve. The essential elements of a reliability specification are:
What is satisfactory performance?
The definition of satisfactory performance must include limits for each case. These are necessary since if the radar falls below the specified limits for each case, it is considered to have failed the reliability requirement. An important consideration in developing the reliability requirement is that it be realistic in terms of real need, yet consistent with current design state-of-the-art. Otherwise, the requirement may be unattainable or attainable only at a significant expenditure of time and money.
What is the mission reliability of an airborne radar system?
The mission reliability for the airborne radar system shall be at least 0.9 for a six hour mission having the typical operational sequence in the appendix defining mission profile.
Why is time important in reliability?
Time is vital to the quantitative description of reliability. It is the independent variable in the reliability function. The system usage from a time standpoint in large measure determines the form of the reliability expression of which time is an integral part.
What is minimum acceptable value?
As a minimum acceptable value below which the customer would find the system totally unacceptable and could not be tolerated in the operational environment a value based upon the operational requirements.
What is reliability in design?
Designs are usually based on specifications. Reliability requirements are typically part of a technical specifications document. They can be requirements that a company sets for its product and its own engineers or what it reports as its reliability to its customers. They can also be requirements set for suppliers or subcontractors. However, reliability can be difficult to specify. It is easy to use "qualitative" language such as, "our product needs to exceed customer expectations" or "our product should be more reliable than its competition." Joseph Juran, a famous quality pioneer, said, "If you don't measure it, you don't manage it." If an organization does not specify reliability goals numerically, it loses control over managing its products' reliability improvements.
What percentile of stress is reliability?
To be able to estimate reliability at the 98 th percentile of the stress level, units would have to be tested at that stress level or, using accelerated testing methods, the units could be tested at different stress levels and the reliability could be projected to the 98 th percentile of the stress.
Can you use a single number to describe a lifetime distribution?
Attempting to use a single number to describe an entire lifetime distribution can be misleading and may lead to poor business decisions.
Is the Weibull distribution symmetrical?
In this example, because the Weibull distribution is not a symmetrical distribution, the MTTFs do not correspond to the 50 th percentile of failures. The actual percentiles can be calculated using the reliability function. The percentile, P, of units that would fail by t = MTTF is:
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 evalu…
Software Reliability Techniques
- Software Reliability is calculated with the help of two different techniques, such as, 1. Prediction Modeling 2. Estimation Modeling
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 1. Software Reliability is used for data preservation. 2. It helps to avoid software failure. 3. Straightforward in the system upgrade process. 4. 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.
Recommended Articles
- This is a guide to Software Reliability. Here we discuss an introduction to Software Reliability, metrics, techniques with respective advantages. You can also go through our other related articles to learn more – 1. Software Design 2. Software Metrics 3. What is Software Testing? 4. Types of Software Testing