These nicknames are derived from adjectives that end in the suffix ILITY, which are commonly used to describe the desired nonfunctional characteristics. For example: performance, security, maintenance, & operability. In the APPENDIX you must include an engineering analysis of any significant decisions regarding tradeoffs between competing attributes. We’ve already covered different types of software requirements, but this time we’ll focus on non-functional ones, and how to approach and document them. Understanding up front how maintainable software needs to be for a certain project is important, due to its impact on your architecture. SEG3101 (Fall 2010). EXAMPLE: [Accessible by people who are hard of hearing] All course lessons will provide a text alternative to audio content. The needs of discrete stakeholder groups are also specified to define what they expect from a particular solution. When eliciting verifiability requirements, consider Verification and Validation techniques that might be used, possible inspection checks, and installability of the system. •Therefore, unless you have unrealistic values, requirements are usually met •Important to know what measures exist! DEFINITION: Installability is the ease with which a software system can be installed, uninstalled, or reinstalled into a target environment. When eliciting access security requirements, consider needs regarding user registration, user authorization, and user authentication. Non functional definition is the criteria that all product’s features should fall under. Efficiency — how well the software system handles capacity, throughput, and response time. Here are some questions to ask yourself as you consider how to structure maintainability requirements. There exists a gap between both types of requirements. These statements are treated as a problem that must be solved. ELICITATION: Modifiability requirements address the user concern for how quickly and cost effectively changes can be made to a software system. An entity with relatively low costs in these areas is considered maintainable whereas an entity with high costs may be considered unmaintainable or "high maintenance." System performance, security, failover, capacity, scalability, usability, and reliability are just a few categories. EXAMPLE: [Student scalability] The RQ Website shall be scalable to accommodate unrestricted growth in the number of students taking on-demand courses. Architectural standards: Accepted standards and design patterns should be used in the construction of the base architecture: 4.2. However, if there were no plans for the ERP system and the lifespan of the price quoting system would be longer, then making the system highly maintainable makes sense. Availability Availability indicates when a system is operational as well as how reliable it is during operational periods. Types of Non-functional Requirements Non-Functional Requirements deal with issues like scalability, maintainability, performance, portability, security, reliability, and many more. When eliciting efficiency requirements, consider needs regarding response time, throughput, process capacity, and storage capacity. Users must change the initially assigned login password immediately after the first successful login. This is - potentially - a lot of non-functional requirements! DEFINITION: Usability is the ease with which the user is able to learn, operate, prepare inputs and interpret outputs through interaction with a software system. This principle is true of all non-functional requirements. When eliciting usability requirements, consider needs regarding ease of entry, ease of learning, ease of handling, likability, and possible metrics. EXAMPLE: [Plug-in upgrades] Installation of plug-in upgrades shall leave all website content and administrator settings unchanged. Make your non-functional requirements testable by combining them. DEFINITION: Safety is the degree to which a software system prevents harm to people or damage to the environment in the intended context of use. Here, are some examples of non-functional requirement: 1. These are attributes that will help you define crucial user expectations and control product quality. Simply said, a non-functional requirement is a specification that describes the system’s operation capabilities and constraints that enhance its functionality. They are also known as quality or supplementary requirements. Nonfunctional categories included in the revision group are flexibility, maintainability, modifiability, scalability, and verifiability. When eliciting portability requirements, consider aspects of portability with regard to data, program, end-user, and developer documentation. Time of servers and other devices shall be synchronized to a reliable reference time. Here is a little explanation to get you into the same page: Non-functional requirement specifies how the system behaves in terms of constraints or prerequisites. Verifiability — the extent to which tests, analysis, and demonstrations are needed to prove that the software system will function as intended. •The chosen values, however, will have an impact on the amount of work during development as well as the number of The rationale for this requirement is that the RQ Admin can make simple course content adjustments without developer assistance. Non-functional requirements have been taken into account if they have had a bad experience in the past. In essence, it tests the way a system or circuit operates, rather than specific behaviors of that system or circuit. Getting them just as nailed down as the functional requirements … When a new lesson video is added it shall by default be non-viewable (video cannot be played unless the course is purchased). Therefore, when thinking about your next project, keep maintainability in mind. DEFINITION: Modifiability is the degree to which changes to a software system can be developed and deployed efficiently and cost effectively. Furthermore, nonfunctional requirements are referred to by the acronym NFR. An example would be a … DEFINITION: Availability is the degree to which users can depend on the system to be up (able to function) during “normal operating times.”. Non-functional requirements examples. • How likely is a change? Nonfunctional categories included in the transition group are installability, interoperability, portability, and reusability. Volere requirements template and non-functional requirements – another view provided by Suzanne and James Robertson which is very useful. But, one of our indicators of the quality of a ‘good’ requirement is that it is testable, so it … Solution requirements. While a system can still work if NFRs are not met, it may not meet user or stakeholder expectations, or the needs of the business. Non-functional requirements are requirements that specify criteria used in evaluating the operation of a system instead of specific behavior as is the case with functional requirements. As you can see from that list, non-functional requirements are often referred to as "-ilities." Join hundreds of other smart people who get tips, tricks, The REVISION group describes the user need for a system that is easy to correct when errors occur, and is easy to add on new functions. DEFINITION: Integrity is the degree to which the data maintained by the software system are accurate, authentic, and without corruption. Non-functional requirements can be derived in many ways, but the best and most industries tried and tested way is from functional requirements. When eliciting reusability requirements, consider aspects of feasibility of software reuse, possible areas for reuse, and development standards. We can restrict the number we document by applying 2 rules: only document the non-functional requirements that apply to the solution - not all solutions will need to specify all non-functional requirements. • When is a change made? Non-Functional Requirements Classification of NFRs Criteria and Factors Portability, Reliability, Performance Example NFR for an Automated Money Machine Information Systems Analysis and Design csc340 2004 John Mylopoulos Non-Functional Requirements -- 2 Non-Functional Requirements --NFRs (also Software Qualities) ELICITATION: Integrity requirements address the user concern for the accuracy and authenticity of the data. EXAMPLE: [Data backup] Customer orders shall be backed up at least once per month to prevent data loss. Sign up for our monthly newsletter below to get more details such as featured articles, upcoming training and webinars, free resources, and best practice advice from our experts. This can be the result of unknown future business process changes, resource constraints, technology upgrades, etc. © Seilevel, Inc. 2019, All Rights Are Reserved. System and Solution Architect and Engineering are often responsible for defining and refining these NFRs.All teams must be aware of the special attributes they’re creating for the system. When eliciting integrity requirements, consider needs regarding routine backups of data to prevent loss, backing up data to multiple locations, data restore procedures, and authenticity of data with respect to the original data source. You don’t need to automate everything some non-functional testing requires a manual approach, those supporting Recoverability and Disaster Recovery in particular. Consider the following needs when eliciting availability requirements: downtime impact on the business, partial availability impact on the business, transparent unavailability, and minimizing unavailability. Testability Analysis Framework for Non-functional Requirements. This may be quite trivial to many, but it is still an indication of the lack of uniformity. The categories presented below are detailed in Roxanne Miller’s book NFR-Group: … As mentioned, clearly defined requirements are the key to project success. What is a Non-Functional Requirement? Therefore, making a large investment into a new price quoting system doesn’t make sense. ELICITATION: Installability requirements address the user concern for how easy it is to install, reinstall, and uninstall a software system. The basic types of non-functional requirements … Transition requirements describe the ability of the software system to adapt to its surrounding environment. Non Functional Requirements: Maintainability, This impact makes maintainability an important. Examples include reliability, availability, portability, scalability, usability, maintainability. When eliciting interoperability requirements consider aspects such as software testing, product engineering, industry partnership, standard implementation, and common technology. EXAMPLE: [Forgotten password] Students may request a temporary password, and shall receive a link sent to their primary email address. Usability: Usability which means that how easy the software performs the specific task.in other words, … 4. ELICITATION: Availability requirements address the user concern for how dependable the system is during normal operating times. There are lots of bells and whistles that have become standard expectations, like calling, emailing, texting, photography, voice activation and notifications. Prior to discussing how requirements are created, let’s differentiate their types. Nonfunctional categories included in the operation group are access security, accessibility, availability, confidentiality, efficiency, integrity, reliability, safety, survivability, and usability. As you can see from that list, non-functional requirements are often referred to as "-ilities." As presented in chapter 4 of The Quest for Software Requirements, the following simplified definition is used in the context of this site: Example: Reduce the risk of missing nonfunctional requirements, Collaborate with others to develop nonfunctional requirements, Apply a user-focused approach to eliciting nonfunctional requirements, Represent nonfunctional requirements in any development environment such as waterfall and agile, Understand factors that contribute to challenges in eliciting nonfunctional requirements. Example u The system shall ensure that data is protected from unauthorised access. The user perceives the system as a set of programmed language statements. Whereas functional requirements convey what features the Product Owner would like built, non functional requirements (NFRs) describe system behaviors, attributes and constraints, and they can fall under multiple categories. Yes, I want a free Nonfunctional Requirement Categories job aid! When eliciting flexibility requirements, consider aspects such as organizational differences, industry differences, country differences, and whether the software system will be used at a single site or multiple sites. The non-functional requirements are also called Quality attributes of the software under development. So it’s important that you analyze the system correctly and figure out all the necessary requirements. User contact with the software system might occur in the following ways: OPERATION, or using the functionality. EXAMPLE: [Probability of Failure on Demand] The RQ Website probability of failure on demand (POFOD) shall be 0.0001 (1 out of 10000 plays) when a student requests to play a course video. NonNon--Functional Requirements Functional Requirements Practices and Recommendations: A Brief Synopsis Why What Some Classification Schemes NFRs and RE Processes Product-Oriented Approach: Some Individual NFRs The NFR Framework Appendix With Rational Unified Process and UML With VolereRequirements Specification Templates Others For the purposes of this article an Availability Requirement is any requirement that is not a functional, data or process requirement concerned with defining the periods when the solution can be u… They specify the quality attribute of the software. Portability — how easily the software system can be transferred from its current hardware or software environment to another environment. "Say you are building a 2BHK house for your customer with a hall and a beautiful lawn, the user needs a hall and double bedroom, does not care about the structure, size and strengrh. This is the ultimate nonfunctional requirements course! How to define non-functional requirements. Modifiability — how easily changes to the system can be developed and deployed in an efficient and cost effective manner. These requirements are not applied individually to each function. Often deciding on quality attributes requires making tradeoffs, e.g., between performance and maintainability. While functional requirements describe what tasks the system is to perform, the operation requirements describe how well the system performs the tasks. A non-functional requirement is an qualitative requirement for a product, service, system, process, document, location, infrastructure component or facility. 5 SEG3101 (Fall 2010). Users who come in contact with the software system by managing the upkeep of the system are generally most concerned with transition requirements. Maintainability — how easily faults in the software system can be found and fixed. DEFINITION: Confidentiality is the degree to which the software system protects sensitive data and allows only authorized access to the data. EXAMPLE: [Video load time] All course lesson videos should load in 2 seconds or less. ELICITATION: Efficiency requirements address the user concern for how fast the system functions, how efficiently the system takes in inputs and processes outputs, and how much can be processed at a time. ELICITATION: Scalability requirements address the user concern for how easy it is to expand or upgrade the system’s capabilities. ELICITATION: Portability requirements address the user concern for how easy it is to transport the system. EXAMPLE: [Update failure detected] When an update failure is detected all updates performed during the failed session shall be rolled back to restore the data to pre-session condition. Users who come in contact with the software system by managing the upkeep of the system are generally most concerned with transition requirements. A functional requirement describes what a software system should do, while non-functional requirements place constraints on how the system will do so.. Let me elaborate. Let us take the example from our Infotainment systems that we have already taken in a few places in this article. A non-functional requirement is an qualitative requirement for a product, service, system, process, document, location, infrastructure component or facility. For those who are not familiar with non-functional requirements. From this point of view, the user is concerned with how well the system operates. EXAMPLE: [No sensitive cardholder retention] The RQ Website will not retain customer credit or debit card information entered during the Checkout payment processing. No doubt also stemming from inconsistent terminology and confusing definitions, we cannot agree on how to spell these important requirements. To clarify how to apply these questions, and the resulting requirements, let’s look at an example: SeiAg is an agricultural company that has a five-year plan to roll out a state-of-the-art ERP. It is designed to test the readiness of a system as per nonfunctional parameters which are never addressed by functional testing. Availability — how dependable the system is able to function during normal operating times. EXAMPLE: [Course page content] RQ Website course marketing pages shall be editable in Cornerstone. This download product is an editable, easy-to-use Microsoft Excel® file of the 2,000+ questions presented in Roxanne Miller’s book, The Quest for Software Requirements. NON-FUNCTIONAL TESTING is defined as a type of Software testing to check non-functional aspects (performance, usability, reliability, etc) of a software application. Reusability — how easily a portion of the software system can be converted for use in another. type of requirement in systems engineering In systems engineering and requirements engineering, a non-functional requirement is a requirement that specifies criteria that can be used to judge the operation of a system, rather than specific behaviors. In the APPENDIX you must include an engineering analysis of any significant decisions regarding tradeoffs between competing attributes. That is, the user is concerned with aspects such as packaging, transport, and compatibility with other systems. The difference between functional and non-functional requirements is not so essential. Its purpose is to stream course lesson videos. Non-functional requirements from Wikipedia – a huge variety of categories for non-functional requirements are suggested and described here. They are the basis of non-functional testing scenarios. EXAMPLE: [Quarterly website upgrades] Routine software upgrades shall be applied no more frequently than once every three months, and whenever possible shall be installed while the RQ Website is active. Scalability — how well the software system is able to expand its processing capabilities upward and outward to support business growth. TRANSITION, or managing the upkeep of the system. Note: for the definition of Non-Functional requirements in general see the article “Non-Functional Requirements”. The revision group comprises the following nonfunctional categories: Flexibility — how easily the software can be modified to adapt to different environments, configurations, and user expectations. At each intersection can be any combination of non-functional requirements. Use this list as a guideline for determining what nonfunctional requirements are required by the system and to define those requirements. Non-functional requirements exist in every system. Such attempt should be reported to the security administrator. The operation group subdivides into the following nonfunctional categories: Access Security — how well the system is safeguarded against deliberate and intrusive faults from internal and external sources. The software user is any person who comes into contact with the software system. When eliciting installability requirements consider aspects such as installation process, people who will perform the install, configuration of the target platform, and types of software. If you’ve ever dealt with non-functional requirements, you may know that differen… We take care to protect your email and other information in the same way we would want our own personal information protected. In order to apply a user-focused approach, it is necessary to understand who the user is. ELICITATION: Confidentiality requirements address the user concern for how well the system protects sensitive data and makes it available to authorized users. Examples of Non-Functional Requirements. DEFINITION: Accessibility is the extent to which the software system can be used by people with the widest range of capabilities to achieve a specified goal in a specified context of use. They are basically the requirements stated by the user which one can see directly in the final product, unlike the non-functional requirements. DEFINITION: Flexibility is the ease in which the software can be modified to adapt to different environments, configurations, or user expectations. LOOKING FOR A NONFUNCTIONAL REQUIREMENTS TEMPLATE? Is this difference even important? (The roll out of corporate memberships will not restrict growth or negatively affect website performance.). Confidentiality — how well the system protects sensitive data and allows only authorized access to the data. Non-Functional Requirements deal with issues like scalability, maintainability, performance, portability, security, reliability, and many more. There is no obligation to purchase. ELICITATION: Access security requirements address the user concern for how well the system is safeguarded against unauthorized access. - Non-functional requirements are constraints on the system or the development process: a) Non-functional requirements may be more critical than functional requirements b) If these are not met, the system is useless. When eliciting confidentiality requirements, consider aspects related to access control, privacy of communication channels, input interfaces, and secure storage of sensitive data. Maintainability are the relative costs of fixing, updating, extending, operating and servicing an entity over its lifetime. It depends on what type of non-functional requirements you are documenting and at what level they apply. EXAMPLE: [Mean preventative maintenance time] The mean preventative maintenance time on applying routine plug-in updates to the RQ Website shall be less than 30 minutes every 2 weeks. As you pore over your requirements document, you may wonder what the difference is between a functional requirement and a non-functional requirement. an order is placed, a customer signs up, etc). When eliciting reliability requirements, consider needs regarding possible causes of system failure, preventative actions or procedures necessary to avoid failure, failure classes, and reliability metrics. • Who does the change? Section 3 Non-Functional Requirements List contains the detailed non-functional ... for example the provision of ... Maintainability is the degree of effectiveness and efficiency with which a product or system can be modified by the intended maintainers. The devil is in the details. Inconsistent terminology, confusing definitions, and the absence of a universally accepted classification scheme make understanding nonfunctional requirements a challenge. On the whole system, Non-functional requirements are applied. These quality assurance attributes of the Product can be considered under the quality component too. Deriving Non-Functional Requirements From Functional Requirements. It is further divided into performance, security, usability, compatibility as the characteristics of the software. We will detail below why the difference isimportant, and dig into how to generate and write thes… I agree to Seilevel’s Privacy Policy *. DEFINITION: Interoperability is the extent to which the software system is able to couple or facilitate the interface with other systems. There is no agreement within various industry groups on what these types of requirements are called. Addressing a user concern will necessitate the formulation of a number of functional requirements, but the user concerns will also act to constrain other requirements that are characteristic of nonfunctional requirements. Receive a FREE copy of the Nonfunctional Requirement Categories quick-reference job aid. Functional and non-functional requirements prioritization empirical evaluation of IPA, AHP-based, and HAM-based approaches.pdf Content uploaded by Mohammad Dabbagh Author content Functional requirements specify specific behaviors of a system and are generally defined in the use cases. Non functional requirements ©Guy Beauchamp/smart-BA 2009 Page 4 of 7 How to document non-functional requirements It depends. When eliciting survivability requirements, consider needs regarding failure detection techniques and fault recovery techniques. The price quoting system has reached the end of its life due to obsolete technology that can no longer be supported. Solution requirements describe the characteristics that a product must have to meet the needs of the stakeholde… Employees never allowed to update their salary information. Interoperability — how well the software system is able to couple or facilitate the interface with other systems. Nonfunctional Requirement – a specification of how well a software system must function. EXAMPLE: [Downloads are easy to access] Students shall have the option to download course materials when viewing a course lesson or the course overview. Stakeholder requirements. ELICITATION: Accessibility requirements address the user concern for how easy the system is to use by people with varying capabilities. If you think of functional requirements as those that define what a system is supposed to do, non functional requirements (NFRs) define constraints which affect how the system should do it.. Non-Functional Requirements are the constraints or the requirements imposed on the system. This attribute is the flexibility with which the application can be modified, … - Selection from Mastering Non-Functional Requirements [Book] For example, consider the cell phone and what it does. ELICITATION: Maintainability requirements address the user concern for how easy it is to upkeep and repair the system. Maintainability Maintainability is the ability of the application to go through changes with a fair degree of effortlessness. EXAMPLE: [Parallel course launch] One or more courses shall be loaded and launched from a neutral party’s website. When eliciting accessibility requirements, consider aspects related to legislation and standards, and specific needs such as visual, hearing, cognitive, and mobility. They serve as constraints on the design of the solution and state which qualities are needed or valuable. They specify criteria that judge the operation of a system, rather than specific behaviours, for example: “Modified data in a database should be … These may be speed, security, reliability, etc. However, four examples of Non-functional requirements we are discussing here are usability, reliability, performance, supportability, and scalability. When eliciting scalability requirements, consider aspects such as ability to cope with increasing processing load, expanding business locations, recycling hardware to minimize waste, and possible causes for degradation. Nonfunctional requirements specify overall characteristics such as cost and reliability. Non-functional requirements address pervasive qualities like performance, reliability, security, and maintainability. This user perceives the system as an electronic tool that helps to automate what would otherwise be done manually. These include high-level statements of goals, objectives, and needs. Non-functional requirements cover all the remaining requirements which are not covered by the functional requirements. They specify criteria that judge the operation of a system, rather than specific behaviours, for example: “Modified data in a database should be … It depends on what type of non-functional requirements you are documenting and at what level they apply. Shift-left as much as you can to de-risk your non-functional requirements. Non-Functional Requirements (NFR) specifies "how well" the "what must behave". Types of Non-functional Requirements Many non-functional requirements will have direct implications to a project in the form of cost implications, performance objectives and future growth potential. ELICITATION: Safety requirements address the user concern for how well the system protects people and the environment from harm. This impact makes maintainability an important non-functional requirement to consider … There is no one standard definition of an Availability Non-Functional Requirement. In this situation, if SeiAg decides to replace the price quoting system with a stop-gap measure, then making the software highly maintainable is not a top priority. - Non-functional requirements are constraints on the system or the development process: a) Non-functional requirements may be more critical than functional requirements b) If these are not met, the system is useless. Integrity — how well the data are maintained by the software system in terms of accuracy, authenticity, and without corruption. DEFINITION: Scalability is the degree to which the software system is able to expand its processing capabilities upward and outward to support business growth. ELICITATION: Survivability requirements address the user concern for the system’s resilience from failure. Non-Functional Requirements Lawrence Chung Department of Computer Science ... for example, software performance requirements, software external interface requirements, design ... – quality of the design: measured in terms such as maintainability, enhanceability, portability. Like many professions, the world of engineering and project management has its own “terms of art” that can be confusing to experts and novices alike. In the Requirement gathering techniques, the focus is on the functional requirement rather than non-functional requirements. Of course, not all non-functional requirements end in "-ility." This FREE, editable MS WORD template is available in the TOOLS and TEMPLATES page under RESOURCES. These are attributes that will help you define crucial user expectations and control product quality. Nonfunctional Requirements. Safety — how well the system prevents harm to people or damage to the environment. The system must be analyzed, modified, and tested as problems arise, or the business changes the way it operates. Maintainability is how easy it is for a system to be supported, changed, enhanced, and restructured over time. Non-Functional requirements Software Quality (2) •An interesting phenomenon: Measurable objectives are usually achieved! 70% must obtain “highly maintainable” and none . DEFINITION: Portability is the ease with which a software system can be transferred from its current hardware or software environment to another environment. This impact makes maintainability an important non-functional requirement to consider when developing software. From this point of view, the system carries similar characteristics as hardware. XIV. Non-functional Requirements capture conditions that do not directly relate to the behaviour or functionality of the solution, but rather describe environmental conditions under which the solution must remain effective or qualities that the systems must have. The Quest for Software Requirements. Often deciding on quality attributes requires making tradeoffs, e.g., between performance and maintainability. When eliciting maintainability requirements, consider aspects such as maintenance performance metrics, maintenance support features, system maintenance features, system complexity, development process, maintenance process cycle, and possible problems. In many cases this can lead to teams using only functional requirements or having to constantly evaluate their non-functional requirements for correctness. 4.1. Nonfunctional Requirements (NFRs) define system attributes such as security, reliability, performance, maintainability, scalability, and usability. Non-Functional Requirements are the constraints or the requirements imposed on the system. Accessibility — how easily people with the widest range of capabilities can use the system. But wait – there’s more: 1. The transition group includes the following nonfunctional categories: Installability — how easily the system can be installed, uninstalled, or reinstalled into a target environment. Non-functional requirements (NFRs) describe the desired behavior of a system from several perspectives that are not directly visible to a functional user. For example, the practice of eliciting user needs will identify a number of non-functional requirements. This parallel launch will help to verify the audio and sound quality of all course lesson videos. DEFINITION: Verifiability is the extent to which tests, analysis, and demonstrations are needed to prove that the software system will function as intended. This compilation is included with the course downloadable materials in the on-demand course Nonfunctional Requirements. So it’s important that you analyze the system correctly and figure out all the necessary requirements. • What can change? DEFINITION: Maintainability is the ease with which faults in a software system can be found and fixed. Non-functional requirements cover all the remaining requirements which are not covered by the functional requirements. The basic types of non-functional requirements … EXAMPLE: [Operation monitoring] The Medication Monitoring System shall not dispense doses of medication that are greater than maximum amount prescribed by the physician. Here are some examples of non-functional requirements: Performance requirements Maintainability; Maintainability describes how well the system can be kept functional and how well it can be changed. The main article on Non-Functional Requirements discusses why the following table is a reasonable tool to use to assess at what level to document non-functional requirements. Addressing a user concern will necessitate the formulation of a number of functional requirements, but the user concerns will also act to constrain other requirements that are characteristic of nonfunctional requirements. Examples include reliability, availability, portability, scalability, usability, maintainability. Hundreds of examples of nonfunctional requirement statements are assembled into an 8-page PDF. ELICITATION: Verifiability requirements address the user concern for how easy it is to show that the system performs its functions. Non-functional requirements examples. Non functional requirements ©Guy Beauchamp/smart-BA 2009 Page 4 of 7 How to document non-functional requirements It depends. If they are not properly addressed, undesirable results occur such as unsatisfied users, developers, and clients, and schedule and budget overruns to correct the software that was developed without the nonfunctional requirements in mind. The 14 categories presented in the book, along with 5 additional categories, are explored in the on-demand course, Nonfunctional Requirements. quick-reference job aid! DEFINITION: Efficiency is the extent to which the software system handles capacity, throughput, and response time. The following are illustrative examples. But our experience has shown that customers mainly consider the functional requirements. N… DEFINITION: Reusability is the extent to which a portion of the software system can be converted for use in another system. NFRs are associated with backlogs at all levels of SAFe, as Figure 1 illustrates.Because NFRs are significant attributes of the solution that the Agile Release Train (ART) and Value Streams create, their most obvious representation is at the program and large solution levels. Understanding up front how maintainable software needs to be for a certain project is important, due to its impact on your architecture.