Requirements analysis
Requirements analysis, in software engineering, is a term used to describe all the tasks that go into the instigation, scoping and definition of a new or altered computer system. Requirements analysis is an important part of the software engineering process; whereby business analysts or software developers identify the needs or requirements of a client; having identified these requirements they are then in a position to design a solution.
Requirements analysis is also known under other names:
- requirements engineering
- requirements gathering
- requirements capture
- operational concept documenting
- system engineering
- requirements specification
During most of the history of software engineering it has been considered to be a relatively easy part of the process. However, in the last decade or so, it has become increasingly recognised as being the most vital part of the process; given that the failure to properly identify requirements makes it virtually impossible for the finished piece of software to meet the needs of the client or be finished on time.
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The challenge
Successfully completing a "requirements analysis" task is a challenge. In the first place, it is not easy to identify all the stakeholders, give them all an appropriate form of input, and document all their input in a clear and concise format. And there are constraints. The requirements engineer is expected to determine whether or not the new system is:
In the rush of enthusiasm associated with a new project, there is always a temptation to downplay the importance of requirements analysis. However, studies of previous projects reveal that costs and technical risks can be reduced through rigorous and thorough up-front requirements engineering.
General problems
The general difficulties involved with requirements analysis are increasingly well known:
- the right people with adequate experience, technical expertise, and language skills may not be available to lead the requirements engineering activities;
- the initial ideas about what is needed are often incomplete, wildly optimistic, and firmly entrenched in the minds of the people leading the acquisition process; and
- the difficulty of using the complex tools and diverse methods associated with requirements gathering may negate the hoped for benefits of a complete and detailed approach.
Stakeholder issues
Steve McConnell, in his book Rapid Development, details a number of ways users can inhibit requirements gathering:
- Users don't understand what they want
- Users won't commit to a set of written requirements
- Users insist on new requirements after the cost and schedule have been fixed.
- Communication with users is slow
- Users often do not participate in reviews or are incapable of doing so.
- Users are technically unsophisticated
- Users don't understand the software development process.
Developer issues
However, developers are equally at blame; and given they are being paid to supply the solution the stakeholder(s) want they have far less excuse. Typical problems caused by software developers are:
- Software developers and the end user often have different vocabularies. Consequently, they can believe they are in perfect agreement until the finished product is supplied. The duty to bridge that gap belongs to the developers, since that is what they are being paid to do.
- Software developers often try to make the requirements fit an existing system or model, rather than develop a system specific to the needs of the client.
- Analysis is often carried out by programmers, rather than business analysts. It is often the case that programmers lack the people skills and the real world knowledge to understand a business process properly.
Solutions
One of the solutions to this problem has been recognising that requirements analysis is a specialist field best carried out by experts, i.e. business or system analysts, who could bridge the gap between the business and IT (Information Technology) worlds. While this approach has helped, it has proved difficult to find staff who possess equally good people and technical skills. In addition, the techniques used to analyse requirements have not proved sufficiently effective.
Modern techniques introduced in the 1990s like Prototyping, UML, use cases, and Agile software development seem to offer more promise.
Main Techniques
Requirements analysis can be a long and arduous process. The requirements specialists do their work by talking to people, documenting their findings, analyzing the collected information to discover inconsistencies and oversights, and then talking to people again. This process can go on for a while, and may continue throughout the life cycle of a system.
New systems change the environment and relationships between people, so it is important to identify all the stakeholders, make sure you take into account all their needs; and ensure they understand the implications of the new systems. Frequently, this objective is not met because:
- there is not enough talking, and important needs are overlooked when the system is implemented; and/or
- there is not enough descriptive feedback, and the users are disappointed by the new system's characteristics.
To keep all these discussions well organized and efficient, the evolving requirements must be documented.
Analysts can employ several techniques to get the requirements from the customer. Historically this has included such things as holding interviews, or holding focus groups (more aptly named in this context as requirements workshops) and creating requirements lists. More modern techniques include Prototyping, and use cases. Hopefully, via a process employing many of these methods, the exact requirements of the stakeholders will be established, so that a system that meets the business needs is produced.
Stakeholder interviews
Stakeholder interviews are obviously necessary in requirement specification. However, in any large system a number of individuals need to be interviewed, which increases the time and cost; but more importantly almost always this reveals major discrepancies with regard to how the existing business process works and how it should work in the future. Also different users might have differing or even contradictory requirements.
Requirement workshops
Therefore where systems are complex the usual method is to use requirement workshops, where the analyst brings the main stakeholders in the system together in order to analyse the system and develop the solution.
Such workshops are ideally carried out off site, so that the stakeholders are not distracted. They usually have a facilitator to keep the process focused, a scribe to document the discussion, and usually make use of a projector and diagramming software. Often multiple workshops are required to bring the process to a successful conclusion.
Requirements workshops are considered to be a very useful technique which can save significant time. However, it can be hard to get all the required stakeholders together at one time.
A more general weakness is that some stakeholders do not contribute forcefully enough in workshops and their requirements will not receive the appropriate attention, inevitably producing a limited solution. Additionally, while requirement workshops are an excellent technique for modelling the existing system, they are not so useful for defining the nature of the solution.
Contract style requirement lists
The most common way of documenting requirements has been contract style requirement lists. In a complex system such requirements lists can run to hundreds of pages. An appropriate metaphor would be an extremely long shopping list. Such lists are very much out of favour in modern analysis; as they have proved spectacularly unsuccessful at achieving their aims; but they are still seen to this day.
Strengths:
- Provides a checklist of requirements.
- Provide a contract between the project sponsor(s) and developers.
- For a large system can provide a high level description.
Weaknesses:
- Such lists can run to hundreds of pages. It is virtually impossible to read such documents as a whole and have a coherent understanding of the system.
- Such requirements lists abstract all the requirements and so there is little context
- This abstraction makes it impossible to see how the requirements fit together.
- This abstraction makes it difficult to identify which are the most important requirements.
- This abstraction means that the more people who read such requirements the more different visions of the system you get.
- This abstraction means that it's extremely difficult to be sure that you have the majority of the requirements. Necessarily, these documents speak in generality; but the devil as they say is in the details.
- These lists create a false sense of mutual understanding between the stakeholders and developers.
- These contract style lists give the stakeholders a false sense of security that the developers must achieve certain things. However, due to the nature of these lists, they inevitably miss out crucial requirements which are identified later in the process. Developers use these discovered requirements to renegotiate the terms and conditions in their favour.
- These requirements lists are no help in system design, since they do not lend themselves to application.
Prototypes
Main article: Prototyping
In the mid-1980s, prototyping became seen as the solution to the requirements analysis problem. Prototypes are mock ups of the screens of an application which allow users to visualize the application that isn't yet constructed. Prototypes help users get an idea of what the system will look like, and make it easier for users to make design decisions without waiting for the system to be built. When they were first introduced the initial results were considered amazing. Major improvements in communication between users and developers were often seen with the introduction of prototypes. Early views of the screens led to fewer changes later and hence reduced overall costs considerably.
However, over the next decade, while proving a useful technique, it did not solve the requirements problem:
- Managers once they see the prototype have a hard time understanding that the finished design will not be produced for some time.
- Designers often feel compelled to use the patched together prototype code in the real system, because they are afraid to 'waste time' starting again.
- Prototypes principally help with design decisions and user interface design. However, they can't tell you what the requirements were originally.
- Designers and end users can focus too much on user interface design and too little on producing a system that serves the business process.
Use cases
Main article: Use case
A use case is a technique for capturing the potential requirements of a new system or software change. Each use case provides one or more scenarios that convey how the system should interact with the end user or another system to achieve a specific business goal. Use cases typically avoid technical jargon, preferring instead the language of the end user or domain expert. Use cases are often co-authored by software developers and end users.
During the 1990s use cases have rapidly become the most common practice for capturing functional requirements. This is especially the case within the object-oriented community where they originated, but their applicability is not restricted to object-oriented systems, because use cases are not object orientated in nature.
Each use case focuses on describing how to achieve a single business goal or task. From a traditional software engineering perspective a use case describes just one feature of the system. For most software projects this means that multiple, perhaps dozens, of use cases are needed to fully specify the new system. The degree of formality of a particular software project and the stage of the project will influence the level of detail required in each use case.
A use case defines the interactions between external actors and the system under consideration to accomplish a business goal. Actors are parties outside the system that interact with the system; an actor can be a class of users, roles users can play, or other systems.
Use cases treat the system as a "black box", and the interactions with system, including system responses, are as perceived from outside the system. This is deliberate policy, because it simplifies the description of requirements, and avoids the trap of making assumptions about how this functionality will be accomplished.
A use case should:
- describe a business task to serve a business goal
- have no implementation-specific language
- be at the appropriate level of detail
- be short enough to implement by one software developer in single release.
Use cases can be very good for establishing the functional requirements; however they are not suited to capturing non-functional requirements.
Stakeholder identification
A major new emphasis in the 1990s has been a focus on the identification of stakeholders. This first step is now seen as critical. In the early days systems were built for the projects sponsor(s), who were usually management types. Many systems have been designed by managers with little or no contributions from the eventual users; these systems have tended to fail horrendously. So within the field of software engineering, in the 1970s and 1980s, the understanding of the term stakeholder widened to first the main users of the system, and then peripheral users. However, in the 1990s the search for stakeholders is taking on a more whole system approach. It is increasingly recognised that stakeholders do not just exist in the organisation the analyst is hired by. Other stakeholders will include:
- those organisations that integrate (or should integrate) horizontally with the organisation the analyst is designing the system for
- any back office systems or organisations
- higher management
Successful identification of the stakeholders ensures that analysis will take into account the right elements.
Literature
- Steve McConnell: Rapid development. Taming wild software schedules. 14th ed. Microsoft Press, Redmond 2001 ISBN 1-556-15900-5
See Also
- Business Process Reengineering
- Systems analysis
- Information technology
- Use Cases
- Process Modelling
- Data Modelling
External links
- Requirements Engineering: A Roadmap (PDF)
- Authors: B. Nuseibeh, S. Easterbrook
- Abstract: This paper presents an overview of the field of software systems requirements engineering (RE). It describes the main areas of RE practice, and highlights some key open research issues for the future.
- Date: 2000
- Guide to the Software Engineering Body of Knowledge
- Project Champion: Leonard Tripp
- Executive Editors: Alain Abran, James W. Moore
- Editors: Pierre Bourque, Robert Dupuis
- Abstract: The objectives of the Guide to the Software Engineering Body of Knowledge project are to:
- characterize the contents of the Software Engineering Body of Knowledge;
- provide a topical access to the Software Engineering Body of Knowledge;
- promote a consistent view of software engineering worldwide;
- clarify the place of, and set the boundary of, software engineering with respect to other disciplines such as computer science, project management, computer engineering and mathematics;
- provide a foundation for curriculum development and individual certification and licensing material.
- Date: 2001
- Writing High Quality Requirement Specifications (PDF)
- Author: Dr. Linda Rosenberg (SATC, NASA)
- Abstract: The requirements specification establishes the basis for all of the project's engineering management and assurance functions. If the quality of the requirements specification is poor, it can give rise to risks in all areas of the project. This workshop will educate project managers and software developers in effective development of quality requirement specifications. It will also provide them with ideas and methods they can incorporate immediately into their project plan and find a productive return in documentation evaluation and comprehension.
- Date: 1999