Requirements Engineering Processes

Syllabus

Definition of Requirement engineering process (REP)

Phases of Requirements Engineering Process:• Requirements elicitation and analysis• Requirements validation• Requirements management

Techniques for Requirements Elicitation

Definitions

Requirements are the descriptions of the services provided by a system for the customer and The constraints under which it operates and is developed.

REP is the process of Discovering, Analyzing, Documenting and Validating the requirements of the system; Each software development process goes through the phase of requirements engineering

Requirements engineering processes

The processes used for RE vary widely depending on the application domain, the people involved and the organisation developing the requirements.

The requirements engineering process

Feasibilitystudy

Requirementselicitation and

analysisRequirementsspecification

Requirementsvalidation

Feasibilityreport

Systemmodels

User and systemrequirements

Requirementsdocument

Phases of Requirements Engineering Process

Feasibility study

A feasibility study decides whether or not the proposed system is worthwhile.

A short focused study that checks• If the system contributes to organisational

objectives;• If the system can be engineered using current

technology and within budget;• If the system can be integrated with other

systems that are used.

Elicitation and analysis

Sometimes called requirements elicitation or requirements discovery.

A people-intensive process . Involves technical staff working with customers to find out

about the application domain, the services that the system should provide and the system’s operational constraints.

May involve end-users, managers, engineers involved in maintenance, domain experts, etc. These are called stakeholders.

Problems of requirements analysis Stakeholders don’t know what they really want. Stakeholders express requirements in their own terms. Different stakeholders may have conflicting

requirements. Organisational and biased factors may influence the

system requirements. The requirements change during the analysis process.

New stakeholders may emerge and the business environment change.

Requirements validation

Concerned with demonstrating that the requirements define the system, that the customer really wants.

Requirements error costs are high so validation is very important• Fixing a requirements error after delivery may cost

up to 100 times the cost of fixing an implementation error.

Requirements checking

Validity. Does the system provide the functions which best support the customer’s needs?

Consistency. Are there any requirements conflicts? Completeness. Are all functions required by the

customer included? Realism. Can the requirements be implemented given

available budget and technology Verifiability. Can the requirements be checked?

Requirements management

Requirements management is the process of managing changing requirements during the requirements engineering process and system development.

Requirements are inevitably incomplete and inconsistent• New requirements emerge during the process as business

needs change and a better understanding of the system is developed;

• Different viewpoints have different requirements and these are often contradictory.

Techniques for Requirements Elicitation

Interviewing Brainstorming Prototyping Requirement Workshop

“When people talk, listen completely. Most people never listen.”

InterviewingInterviews are the commonly used and most popular method for requirements elicitation . In this method the analyst and the engineers of the requirements engineering process discuss with the different types of stake holders to understand the requirements of the system and the objective they have to fulfil in the system . There are typically 2 main types of interviews

1. Closed Interview: In this interview the requirements engineer prepare some predefined questions and he tries to get the answers for these questions from the stake holders.

2. Open interview: In this interview the requirements engineer does not

prepare any predefined questions, and he tries to get the information from the stakeholders in open discussions. He mostly concentrates on finding the stake holders expectations on the system.

Brainstorming Brainstorming is a techniques used to generate new ideas and find the

solution to a specific issue. This is conducted as a conference with six to ten members. The members are from the different departments and domain experts are

also included. This conference is headed by the organizer, who states the issue to be

discussed. The conference is generally held in a round table fashion. Every member person is allotted with certain time interval to explain

their ideas. Notepads are provided to all members to write their ideas and suggestions. The team of brainstorming will then decide the best idea by voting from

the group and that idea is selected as the solution to the issue discussed in the conference.

Brainstorming can be used to answer the following questions • What exactly the system should provide ?• What are the business and organization rules required to follow ?• What type of questions should be there in the interviews and

questionnaires? • What are the risk factors effect the proposed system development and

what to do avoid that?

Prototyping The Prototype is the representations or visualizations of the actual system

parts . The prototype is designed in the early stages of the implementation of the

project. It provides the General idea of the actual system functions and the work flow. Prototyping is used to gather the requirements from the users by presenting GUI based system functions.

Main aim of Requirements Elicitation is to gather the requirements before the

product is developed. But it is difficult to discover the additional requirements until it comes in to usage or some body is actually using it.

The process of gathering the requirements from the stakeholders and the end users is limited and it is difficult to discover their expectations and the requirements on the new product with out providing some model that resembles the appearance of the real product.

A prototype represents the actual product in both functional and graphical sense .

It provides the flexibility to the users and the stake holders to work with the initial version of the product to understand the system and discuss them to think of the additional and missed requirements.

Prototyping is a most expensive than the all other methods of requirements elicitation

Requirements workshop

A requirements workshop is a structured, facilitated event in which a carefully selected group of stakeholders work together to discover, create, verify, and document predefined requirements deliverables, or work products.

The group is comprised a balanced mix of business and IT people and is led by a neutral facilitator.

The most successful workshops are collaborative. This means that the group joins together to create work products designed to achieve their common goal.

These workshop participants are productive because collectively they have the right mix of skills and knowledge to create the work products.

Members of the group act interdependently, relying on one other’s knowledge, experience, skills, and perspectives – they are motivated to act together.

Key points

The requirements engineering process includes a feasibility study, requirements elicitation and analysis, requirements specification and requirements management.

Requirements elicitation and analysis is iterative involving domain understanding, requirements collection, classification, structuring, prioritisation and validation.

Systems have multiple stakeholders with different requirements.

Key points

Social and organisation factors influence system requirements.

Requirements validation is concerned with checks for validity, consistency, completeness, realism and verifiability.

Business changes inevitably lead to changing requirements.

Requirements management includes planning and change management.