Concept: Requirements Management

What is Requirements Management?

Requirements management is a systematic approach to finding, documenting, organizing and tracking the changing requirements of a system.

We define a requirement as:

A condition or capability to which the system must conform.

Our formal definition of requirements management is that it is a systematic approach to the following:

Eliciting, organizing, and documenting the requirements of the system
Establishing and maintaining agreement between the customer and the project team on the changing requirements of the system

Keys to effective requirements management include maintaining a clear statement of the Requirements, along with applicable attributes for each requirement type and Traceability to other requirements and other project work products.

Collecting requirements may sound like a rather straightforward task. In real projects, however, you will run into difficulties because:

Requirements are not always obvious, and can come from many sources.
Requirements are not always easy to express clearly in words.
There are many different types of requirements at different levels of detail.
The number of requirements can become unmanageable if not controlled.
Requirements are related to one another and also to other work products of the software engineering process.
Requirements have unique properties or property values. For example, they are neither equally important nor equally easy to meet.
There are many interested parties, which means requirements need to be managed by cross-functional groups of people.
Requirements change.

So, what skills do you need to develop in your organization to help you manage these difficulties? We have learned that the following skills are important to master:

Problem analysis
Understanding stakeholder needs
Defining the system
Managing scope of the project
Refining the system definition
Managing changing requirements

Problem Analysis

Problem analysis is done to understand problems, initial stakeholder needs, and propose high-level solutions. It is an act of reasoning and analysis to find "the problem behind the problem". During problem analysis, agreement is gained on the real problem(s), and who the stakeholders are. Also, you define what from a business perspective are the boundaries of the solution, as well as business constraints on the solution. You should also have analyzed the business case for the project so that there is a good understanding of what return is expected on the investment made in the system being built.

Understanding Stakeholder Needs

Requirements come from many sources; examples would be customers, partners, users, and domain experts. You need to know how to best determine what the sources should be, get access to those sources, and also how to best elicit information from them. The individuals who provide the primary sources for this information are referred to as stakeholders in the project. If you're developing an information system to be used internally within your company, you may include people with user experience and business domain expertise in your development team. Very often you will start the discussions at a business model level rather than a system level. If you're developing a product to be sold to a market place, you may make extensive use of your marketing people to better understand the needs of customers in that market.

Elicitation activities may occur using techniques such as interviews, brainstorming, conceptual prototyping, questionnaires, and competitive analysis. The result of the elicitation would be a list of requests or needs that are described textually and graphically, and that have been given priority relative one another.

Defining the System

To define the system means to translate and organize the understanding of stakeholder needs into a meaningful description of the system to be built. Early in system definition, decisions are made on what constitutes a requirement, documentation format, language formality, degree of requirements specificity (how many and in what detail), request priority and estimated effort (two very different valuations usually assigned by different people in separate exercises), technical and management risks, and initial scope. Part of this activity may include early prototypes and design models directly related to the most important stakeholder requests. The outcome of system definition is a description of the system that is both natural language and graphical.

Managing the Scope of the Project

To efficiently run a project, you need to carefully prioritize the requirements, based on input from all stakeholders, and manage its scope. Too many projects suffer from developers working on so called "Easter eggs" (features the developer finds interesting and challenging), rather than early focusing on tasks that mitigate a risk in the project or stabilize the architecture of the application. To make sure that you resolve or mitigate risks in a project as early as possible, you should develop your system incrementally, carefully choosing requirements to for each increment that mitigates known risks in the project. To do so, you need to negotiate the scope (of each iteration) with the stakeholders of the project. This typically requires good skills in managing expectations of the output from the project in its different phases. You also need to have control of the sources of requirements, of how the work products of the project look, as well as of the development process itself.

See also Activity: Activity: Manage the Scope of the System.

Refining the System Definition

The detailed definition of the system needs to be presented in such a way that your stakeholders can understand, agree to, and sign off on it. It needs to cover not only functionality, but also compliance with any legal or regulatory requirements, usability, reliability, performance, supportability, and maintainability. An error often committed is to believe that what you feel is complex to build needs to have a complex definition. This leads to difficulties in explaining the purpose of the project and the system. People may be impressed, but they will not give good input since they don't understand. You should put lots effort into understanding the audience for the documents you are producing to describe the system. You may often see a need to produce different kinds of descriptions for different audiences.

We have seen that the use-case methodology, often in combination with simple visual prototypes, is a very efficient way of communicating the purpose of the system and defining the details of the system. Use cases help put requirements into a context; they tell a story of how the system will be used.

Another component of the detailed definition of the system is to state how the system should be tested. Test plans and definitions of what tests to perform tell us what system capabilities will be verified.

Managing Changing Requirements

No matter how careful you are about defining your requirements, there will always be things that change. What makes changing requirements complex to manage is not only that a changed requirement means that more or less time has to be spent on implementing a particular new feature, but also that a change to one requirement may have an impact on other requirements. You need to make sure that you give your requirements a structure that is resilient to changes, and that you use traceability links to represent dependencies between requirements and other work products of the development lifecycle. Managing change includes activities like establishing a baseline, determining which dependencies are important to trace, establishing traceability between related items, and change control.

See also Activity: Manage Changing Requirements.

More Information

More Information on this topic can be found at:

Concept: Requirements
Concept: Types of Requirements
Concept: Traceability
Whitepaper: Applying Requirements Management with Use Cases