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- Herausgeber: Packt Publishing
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
Non-functional Requirements are key to any software/IT program and cannot be overlooked or ignored. This book provides a comprehensive approach to the analysis, architecture, and measurement of NFRs. It includes considerations for bespoke Java, .NET, and COTS applications that are applicable to IT applications/systems in different domains.
The book outlines the methodology for capturing the NFRs and also describes a framework that can be leveraged by analysts and architects for tackling NFRs for various engagements.
This book starts off by explaining the various KPIs, taxonomies, and methods for identifying NFRs. Learn the design guidelines for architecting applications and systems relating to NFRs and design principles to achieve the desired outcome. We will then move on to various key tiers/layers and patterns pertaining to the business, database, and integrating tiers. After this, we will dive deep into the topics pertaining to techniques related to monitoring and measurement of NFRs, such as sizing, analytical modeling, and quality assurance.
Lastly, we end the book by describing some pivotal NFRs and checklists for the software quality attributes related to the business, application, data, and infrastructure domains.
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Veröffentlichungsjahr: 2017
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Copyright
Mastering Non-Functional Requirements
Copyright © 2017 Packt Publishing
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First published: May 2017
Production reference: 1150517
ISBN 978-1-78829-923-7
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Credits
Author
Sameer Paradkar
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About the Author
Sameer Paradkar is an enterprise architect with 15+ years of solid experience in the ICT industry which spans across consulting, systems integration, and product development. He is an Open Group TOGAF, Oracle Master Java EA, TMForum NGOSS, IBM SOA Solutions, IBM Cloud Solutions, IBM MobileFirst, ITIL Foundation V3 and COBIT 5 certified enterprise architect. He serves as an advisory architect on enterprise architecture programs and continues to work as a subject matter expert. He has worked on multiple architecture transformations and modernization engagements in the USA, UK, Europe, Asia Pacific and the Middle East Regions that presented a phased roadmap to the transformation that maximized the business value while minimizing risks and costs.
Sameer is part of IT Strategy and Transformation Practice in AtoS. Prior to AtoS, he has worked in organizations such as EY - IT Advisory, IBM GBS, Wipro Consulting Services, Tech Mahindra, and Infosys Technologies and specializes in IT strategies and enterprise transformation engagements.
I would like to dedicate this book to my wife, family members and friends for their encouragement, support and love.
Many people throughout my career have directly and indirectly contributed to this book. I would like to take this opportunity to acknowledge their contribution, influence, and inspiration. I believe I am lucky to have found opportunities to work with extremely talented and exceptions individuals who extended their wholehearted support throughout my career. My eternal thanks to them for believing in me and providing exciting opportunities. I would like to thank my team members, chief and lead architects, mentors, discussion partners, reviewers, and supporters, whose valuable comments and feedback have significantly contributed to this book. I look forward to your comments and valuable inputs on an on-going basis. I would like to recognize and thank my current and former colleagues who made my corporate journey exciting, enriching and fulfilling.
About the Reviewer
James D. Miller is an IBM certified expert, creative innovator and accomplished Director, Sr. Project Leader and Application/System Architect with +35 years of extensive applications and system design and development experience across multiple platforms and technologies. Experiences include introducing customers to new and sometimes disruptive technologies and platforms, integrating with IBM Watson Analytics, Cognos BI, TM1 and Web architecture design, systems analysis, GUI design and testing, Database modelling and systems analysis, design, and development of OLAP, client/server, web and mainframe applications and systems utilizing; IBM Watson Analytics, IBM Cognos BI and TM1 (TM1 rules, TI, TM1Web and Planning Manager), Cognos Framework Manager, dynaSight--ArcPlan, ASP, DHTML, XML, IIS, MS Visual Basic and VBA, Visual Studio, PERL, SPLUNK, WebSuite, MS SQL Server, ORACLE, SYBASE Server, and so on.
Responsibilities have also included all aspects of Windows and SQL solution development and design including: analysis; GUI (and Web site) design; data modelling; table, screen/form and script development; SQL (and remote stored procedures and triggers) development/testing; test preparation and management and training of programming staff. Other experience includes development of ETL infrastructure such as data transfer automation between mainframe (DB2, Lawson, Great Plains, and so on) systems and client/server SQL server and Web based applications and integration of enterprise applications and data sources.
Mr. Miller has acted as Internet Applications Development manager responsible for the design, development, QA and delivery of multiple Web Sites including online trading applications, warehouse process control and scheduling systems, administrative and control applications. Mr. Miller also was responsible for the design, development and administration of a Web based financial reporting system for a 450 million dollar organization, reporting directly to the CFO and his executive team.
Mr. Miller has also been responsible for managing and directing multiple resources in various management roles including project and team leader, lead developer and applications development director.
Jim has authored Cognos TM1 Developers Certification Guide, Mastering Splunk, Learning IBM Watson Analytics and a number of whitepapers on best practices such as Establishing a Center of Excellence and continues to post blogs on a number of relevant topics based upon personal experiences and industry best practices.
Jim is a perpetual learner continuing to pursue experiences and certifications, currently holding the following current technical certifications:
IBM Certified Business Analyst - Cognos TM1
IBM Cognos TM1 Master 385 Certification (perfect score 100% on exam)
IBM Certified Advanced Solution Expert - Cognos TM1
IBM Cognos TM1 10.1 Administrator Certification C2020-703 (perfect score 100% on exam)
IBM OpenPages Developer Fundamentals C2020-001-ENU (98% on exam)
IBM Cognos 10 BI Administrator C2020-622 (98% on exam)
IBM Cognos 10 BI Professional C2020-180
Specialties: The evaluation and introduction of innovative and disruptive technologies, Cloud migration, IBM Watson Analytics, Big Data, Data Visualizations, Cognos BI and TM1 application Design and Development, OLAP, Visual Basic, SQL Server, Forecasting and Planning; International Application Development, Business Intelligence, Project Development and Delivery and process improvement.
I would like to thank Nanette L. Miller who is always on my mind and always in my heart…
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Table of Contents
About the Reviewer
Preface
What this book covers
Who this book is for
Conventions
Reader feedback
Customer support
Errata
Piracy
Questions
Understanding NFRs
Introducing NFRs
Performance
Scalability
Availability
Capacity
Security
Maintainability
Manageability
Reliability
Extensibility
Recovery
Interoperability
Usability
Summary
Taxonomy and Framework for NFRs
Taxonomy of non-functional requirements
Non-functional requirements framework
NFR life cycle
Analysis and planning for NFRs
Architecture for NFR
Engineering for NFRs
Monitoring and improvements - NFRs
NFRs KPI and KRA examples
Performance
Scalability
Availability
Capacity
Security
Maintainability
Manageability
Reliability
Extensibility
Recovery
Interoperability
Usability
Summary
Methodology Eliciting - Non Functional Requirements
Methodology discovering non-functional requirements
Stakeholder goals
Legacy system restraints
Market scan of software qualities
Domain trends
Requirements templates and catalogues
Summary
Solutions Addressing NFRs
NFR modeling methodology
Performance
Key drivers
Methodology
Solution options
Checklist
KPIs
Scalability
Key drivers
Methodology
Solution options
Checklist
KPIs
Availability
Key drivers
Methodology
Solution options
Checklist
KPIs
Capacity
Key drivers
Methodology
Solution options
Checklist
KPIs
Security
Key drivers
Methodology
Solution options
Checklist
KPIs
Maintainability
Key drivers
Methodology
Solution options
Checklist
KPIs
Manageability
Key drivers
Methodology
Solution options
Checklist
KPIs
Reliability
Key drivers
Methodology
Solution options
Checklist
KPIs
Extensibility
Key drivers
Methodology
Solution options
Checklist
KPIs
Recovery
Key drivers
Methodology
Solution options
Checklist
KPIs
Interoperability
Key drivers
Methodology
Solution options
Checklist
KPIs
Usability
Key drivers
Methodology
Solution options
Checklist
KPIs
Summary
Architectural Patterns and its Impact on NFRs
Core architecture patterns
Component-based architecture
Context
Drivers
Solution
Impact on NFR's
N-tier architecture
Context
Drivers
Solution
Impact on NFRs
Message Bus
Context
Drivers
Solution
Impact on NFRs
Service-oriented architecture
Context
Drivers
Solution
Impact on NFRs
Business tier patterns
Active/Passive clustering
Context
Drivers
Solution
Impact on NFRs
Load-balancing architecture
Context
Drivers
Solution
Impact on NFRs
Session failover
Context
Drivers
Solution
Impact on NFRs
Resource pooling
Context
Drivers
Solution
Impact on NFRs
Caching
Context
Drivers
Solution
Impact on NFRs
Database tier patterns
Data replication
Context
Drivers
Solution
Impact on NFRs
Connection pooling
Context
Drivers
Solution
Impact on NFRs
Reporting
Context
Drivers
Solution
Impact on NFRs
Information security
Context
Drivers
Solution
Impact on NFRs
Integration tier patterns
Logging and exception management
Context
Drivers
Solution
Impact on NFRs
Enterprise Monitoring and Management
Context
Drivers
Solution
Impact on NFRs
Demilitarized zone
Context
Drivers
Solution
Impact on NFRs
Summary
Sizing, Measurement and Monitoring
NFR - Sizing
NFR - Analytical modeling
NFR - Simulation
Enterprise Monitoring and Management - EMM
Challenges faced by the ASM teams:
Monitoring landscape
Functionality - dimensions
End-user experience monitoring
Real user monitoring:
Synthetic
Discovery, modeling, and display
User defined transactions
Component deep dive monitoring
Application performance analytics
Monitoring tools - managing the problem
APM dashboard
APM future roadmap
Summary
Understanding Pivotal NFRs and Closing Thoughts
Pivotal NFRs
Pivotal NFRs KPI and framework
Pivotal NFR classification
Integrity
Infrastructure domain
Business domain
Application domain
Data domain
Infrastructure domain
Business continuity
Business domain
Application domain
Data domain
Infrastructure domain
Resilience
Business domain
Application domain
Data domain
Infrastructure domain
Confidentiality
Business domain
Application domain
Data domain
Integratability
Business domain
Application domain
Data domain
Infrastructure domain
Robustness
Business domain
Application domain
Data domain
Infrastructure domain
Auditability
Business domain
Application domain
Data domain
Flexibility
Business domain
Application domain
Data domain
Infrastructure domain
Portability
Application domain
Data domain
Infrastructure domain
Reusability
Business domain
Application domain
Data domain
Infrastructure domain
Testability
Business domain
Application domain
Data domain
Infrastructure domain
Accessibility
Business domain
Application domain
Closing thoughts
Audit and accountability
Architecture reviews and risks
Audit and business objectives
Summary
Preface
Maintaining software is hard and therefore expensive and IT departments are often under funded. However, if they are in a just do it mode then non-functional requirements are easy to be forgotten. The consequences of leaving these NFRs lead directly to the aforementioned maintenance problems and increased technical debt.
NFRs are necessary to completing the story of the IT application. While you might consider two or three important NFRs (like performance and security), you’ll probably not cover the others extensively enough, or you might miss out on them all together. And if you do allocate time to deal with them, when the project schedule slips, the NFRs may be the first thing to get drop. So, whether you plan for NFRs or not, chances are high you won’t cover them 100% of the time. You should try to avoid adding technical debt and maintenance nightmares to your future portfolio.
NFRs are key to any software/IT program. They cannot be overlooked or ignored. The book provides a comprehensive approach from analysis, architecture and measurement of non-functional requirements. The book outlines the methodology for capturing the NFRs and also describes a taxonomy framework that can leveraged by analyst and architects for tackling NFRs on engagements.
To summarize, the key differentiators for the book are:
Covers all the three stages of non-functional requirements that is, analysis, architecture and measurement.
NFR framework and taxonomy provides guidance around the modelling phase for the NFRs
Describes the process for capturing and analyzing the KPI and KRAs. These are the key metrics that are required by different stakeholders.
Trade-offs between various NFRs are covered as part of the title
Describes the application performance management domain which is a key practice for managing and monitoring of enterprise applications that helps monitor and analyze NFR KPIs and KRAs as part of the ongoing process.
Coverage of the book:
This book covers areas pertaining to analysis, architecture and measurement of non-functional requirements. A topic with-out which software systems cannot be build or deployed. NFRs are a life-line of any software application and capturing and addressing them is a critical activity in any IT project. The topic in itself is very critical and applicable for IT systems/applications for various industry verticals. The book provides a comprehensive approach from analysis, architecture and measurement of non-functional requirements.
Part I - Analysis:
The books provides and introduction of NFRs and why NFRs are a critical for building software systems. The next section describes the taxonomy of NFRs that is, scalability, availability, reliability and so on. The books outlines various methodology for capturing the NFRs, The books also outlines and describes a framework that can leveraged by analyst and architects for tackling NFRs for various engagements. The framework will focus on the KPIs and KRA for each of the NFRs which will be the key input for solution design phase. The NRF framework will focus on the most critical NFRs applicable for any given situation and any industry.
Part II - Architecture:
This section focus on the solution part of the NFRs providing insights into how they will be addressed in the solution design phase. The book covers key NFRs that are most critical for any project and for each NFR provides the various alternatives pertaining to the solution, the design principle that needs to be applied to achieve the desired outcome for example, high availability or scalability or reliability as covered. The book includes considerations for bespoke (Java, .NET) and COTS applications and are applicable to any IT applications/systems in different domains.
Part III - Assessment:
This part deals with the measurement of NFRs. This outlines the methodology for NFRs measurement. This sections also describes the trade-offs between various NFRs and the best practices to be applied on engagements.
What this book covers
Chapter 1, Understanding NFRs, the chapter provides and introduction of NFRs and why NFRs are a critical for building software systems. The chapter also explains the various KPI for each of the key of NFRs that is, scalability, availability, reliability and so on. The book covers the most critical 24 NFRs that are applicable for IT applications and systems.
Chapter 2, Taxonomy and Framework for NFRs, this chapter describes the taxonomy of NFRs that is, scalability, availability, reliability and so on. The chapter outlines entire life cycle of NFRs, The chapter describes a framework that can leveraged by business analyst and architects for discovering NFRs on various engagements. The framework will focus on the KPIs and KRA for each of the NFRs which will be the critical input for the solution design phase.
Chapter 3, Methodology Eliciting - Non Functional Requirements, this chapter outlines methodology for discovering (elicitations) NFRs. The chapter describes a framework that can be leveraged by business analyst for elicitations of NFRs. The chapter also outlines a framework for prioritization of NFRs. The output of this stage will be the critical input for the solution architecture phase.
Chapter 4, Solutions Addressing NFRs, this chapter outlines the solutioning part of the NFRs providing insights, guidance and principles for architecting NFRs. The book covers all the key NFRs that are critical for any project and for each NFR provides the various alternatives pertaining to the solutioning and the design principles that need to be applied to achieve the desired outcome for example, high availability or scalability or reliability and so on. The book includes considerations for bespoke (Java, .Net) and COTS applications and are applicable to any IT applications/systems in different domains.
Chapter 5, Architectural Patterns and its Impact on NFRs, this chapter outlines the patterns for NFRs providing insights into architecting NFRs. The chapter covers all the key tiers / layers that are critical for any project and describes various patterns pertaining to the business, database and integration tiers. This also covers impact on various NFRs. This chapter describes the trade-offs between various NFRs and the best practices to be applied on engagements.
Chapter 6, Sizing, Measurement and Monitoring, this chapter deals with the measurement of NFRs. This outlines four methodologies for NFRs monitoring and measurement. These include sizing, analytical modelling, quality assurance and monitoring and management. This chapter also describes the approach in depth for monitoring and measuring NFRs.
Chapter 7, Understanding Pivotal NFRs and Closing Thoughts, this chapter provides an introduction to the pivotal NFRs. The chapter explains the various KPI for each of the pivotal NFRs. This is the final chapter of the book and provides summary and trends for the NFR domain. This also outlines architecture assessment and NFR measurement methodology.
Who this book is for
The primary audiences for this title are the gamut of roles starting from IT consultant to Chief Architect who are responsible to deliver strategic, tactical and operational engagements for fortune 100 customers worldwide. Non-functional requirements are the key to any software/IT program. They cannot be overlooked or ignored. The book provides a comprehensive approach from analysis, architecture and measurement of non-functional requirements. The book includes considerations for bespoke (Java, .Net and COTS applications). These are applicable to IT applications from various domains. The book outlines the methodology for capturing the NFRs and also describes a framework that can leveraged by analyst and architects for tackling NFRs for various engagements. The audiences for this book include:
Business Analyst
Enterprise Architects
Business Architects
Solution Architects
Technical Architects/Designers
Domain/Security/Integration Architects
Software Developers, Support Engineers & Test Engineers
Technical Project Managers
Project Leads/Technical Leads/Technical Project Managers
Students - Computer Science/IT Stream
Conventions
In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.
New terms and important words are shown in bold.
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Understanding NFRs
The non-functional requirements are those aspects of the IT system that, while not directly affecting the business functionality of the application but have a profound impact on the efficiency and effectiveness of business systems for end users, as well as the people responsible for supporting the program.
The definition of these requirements is an essential factor in developing a total customer solution that delivers business goals. The non-functional requirements (NFRs) are used primarily to drive the operational aspects of the architecture; in other words, to address major operational and technical areas of the system to ensure the robustness and ruggedness of the application.
Benchmark or proof of concept (POC) can be used to verify if the implementation meets these requirements or to indicate if a corrective action is necessary. Ideally, a series of tests should be planned that maps to the development schedule and grows in complexity.
The topics that are covered in this chapter are as follows:
Definition of NFRs
NFR KPI and metrics
Introducing NFRs
The following pointers state the definition of NFRs:
To define requirements and constraints on the IT system
As a basis for cost estimates and early system sizing
To assess the viability of the proposed IT system
As an important determining factor of the architecture and design of the operational models
As a guideline to design phase to meet NFRs such as performance, scalability, and availability
The NFRs for each of the domains, for example, scalability, availability, and so on, must be understood to facilitate the design and development of the target operating model. These include the servers, networks, and platforms including the application runtime environments. These are critical for the execution of benchmark tests. They also affect the design of technical and application components.
End users have expectations about the effectiveness of the application. These characteristics include ease of software use, speed, reliability, and recoverability when unexpected conditions arise. The NFRs define these aspects of the IT system.
The NFRs should be defined precisely and this involves quantifying them. NFRs should provide measurements which the application must meet. For example, the maximum number of time allowed to execute a process, the number of hours in a day an application must be available, the maximum size of a database on disk, and the number of concurrent users supported are typical NFRs the software must implement.
There are many kinds of non-functional requirements.
Performance
Performance is the responsiveness of the application to perform specific actions in a given time span. Performance is scored in terms of throughput or latency. Latency is the time taken by the application to respond to an event. Throughput is the number of events scored in a given time interval. An application's performance can directly impact its scalability. Enhancing an application's performance often enhances scalability by reducing contention for shared resources.
Performance attributes specify the timing characteristics of the application. Certain features are more time-sensitive than others; the NFRs should identify such software tasks that have constraints on their performance. Response time relates to the time needed to complete specific business processes, batch or interactive, within the target business system.
The system must be designed to fulfill the agreed upon response time requirements, while supporting the defined workload mapped against the given static baseline, on a system platform that does not exceed the stated utilization.
The following attributes are:
Throughput
: The ability of the system to execute a given number of transactions within a given unit of time
Response times
: The distribution of time which the system takes to respond to the request
Scalability
Scalability is the ability to handle an increase in the workload without impacting the performance, or the ability to quickly expand the architecture.
It is the ability to expand the architecture to accommodate more users, more processes, more transactions, and additional systems and services as the business requirements change and the systems evolve to meet the future business demands. This permits existing systems to be extended without replacing them. This directly affects the architecture and the selection of software components and hardware.
The solution must allow the hardware and the deployed software services and components to be scaled horizontally as well as vertically. Horizontal scaling involves replicating the same functionality across additional nodes; vertical scaling involves the same functionality across bigger and more powerful nodes. Scalability definitions measure volumes of users and data which the system should support.
There are two key techniques for improving both vertical and horizontal scalability:
Vertical scaling is also known as
scaling up
and includes adding more resources such as memory, CPU, and hard disk to a system
Horizontal scaling is also known as
scaling out
and includes adding more nodes to a cluster for workload sharing
The following attributes are:
Throughput
: Number of maximum transactions your system needs to handle for example, a thousand a day or a million
Storage
: Amount of data you are going to need to store
Growth requirements
: Data growth in the next 3-5 years
Availability
Availability is the time frame in which the system functions normally and without failures. Availability is measured as the percentage of total application downtime over a defined time period. Availability is affected by failures, exceptions, infrastructure issues, malicious attacks, and maintenance and upgrades.
It is the uptime or the amount of time the system is operational and available for use. This is specified because some systems are architected with expected downtime for activities like database upgrades and backups.
Availability also conveys the number of hours or days per week or weeks per year the application will be available to its end customers, as well as how rapidly it can recover from faults. Since the architecture establishes software, hardware, and networking entities, this requirement extends to all of them. Hardware availability, recoverability, and reliability definitions measure system uptime.
For example, it is specified in terms of Mean Time Between Failures (MTBF).
The following attributes are:
Availability
: Application availability considering the weekends, holidays, and maintenance times and failures
Locations of operation
: Geographic location, connection requirements, and if the restrictions of the network prevail
Offline requirement
: Time available for offline operations including batch processing and system maintenance
Length of time between failures
: This
is the predicted elapsed time between inherent
failures
of a system during operation
Recoverability
: Time required by the system to resume operation in the event of failure
Resilience
: The reliability characteristics of the system and sub-components
Capacity
This NFR defines the ways in which the system is expected to scale-up by increasing capacity, hardware, or adding machines based on business objectives.
Capacity is delivering enough functionality required for the end users. A request for a web service to provide 1,000 requests per second when the server is only capable of 100 requests a second, may not succeed. While this sounds like an availability issue, it occurs because the server is unable to handle the requisite capacity.
A single node may not be able to provide enough capacity, and one needs to deploy multiple nodes with a similar configuration to meet organizational capacity requirements. Capacity to identify a failing node and restart it on another machine or VM is a NFR.
The following attributes are:
Throughput is the number of peak transactions the system needs to handle
Storage is the volume of data the system can persist at runtime to disk and relates to the memory/disk
Year-on-year growth requirements (users, processing, and storage)
The e-channel growth projections
Different types of things (for example, activities or transactions supported, and so on)
For each type of transaction, volumes on an hourly, daily, weekly, monthly basis, and so on
During the specific time of the day (for example, at lunch), week, month, or year are volumes significantly higher
Transaction volume growth expected and additional volumes you will be able to handle
Security
Security is the ability of an application to avoid malicious incidences and events outside of the designed system usage, and prevent disclosure or loss of information. Improving security increases the reliability of an application by reducing the likelihood of an attack succeeding and impairing operations. Adding security controls protects assets and prevents unauthorized access and manipulation of critical information. The factors that affect an application security are confidentiality and integrity. The key security controls used to secure systems are authorization, authentication, encryption, auditing, and logging.
Definition and monitoring of effectiveness in meeting the security requirements of the system, for example, to avoid financial harm in accounting systems, is critical. Integrity requirements restrict access to functionality or data to certain users, and protect the privacy of data entered into the software.
The following attributes are:
Authentication
: Correct identification of parties attempting to access systems and protection of systems from unauthorized parties
Authorization
