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This tutorial explains the basics of Requirements Engineering

1. What is Requirements Engineering

Requirements Engineering (RE) defines the process of the defining, documenting, maintaining and Validate requirements. In order to define a requirement different methods can be used.

2. User stories

A user story is a requirement which is written by the user or customer of the software. They are written in simple words and should not be longer than two sentences. User stories are used in agile software development projects.

A template for a user story could look like this:

  • As a <type of user>, I want <goal> to <reason>.

  • As a <type of user>, I want <goal>.

3. Epic

An epic is the description of a big requirement. The structure of an epic is like the structure of a user story. It contains multiple user stories.

4. Use cases

Use cases are a definition of actions on how a user will interact with a software to achieve a goal. The actions are described step by step to define the process that a user will go through to complete the goal. Use cases do not only describe the correct steps, they also state the errors that the user could encounter on its way to achieve the goal.

They can consist of only text or also include UML (Unified Modeling Language) diagrams.

There is not a standard way to write use cases and each project needs to set a a template that fulfills the needs of the project. A possible template for a use case could look like this:

  • Title

  • Id - this should be unique

  • Brief Description - A maximum of two sentences, similar to a user story

  • Level - Possibe options: High Level Summary, Summary, User Goal, Sub-Function, Low Level

  • Actors - Roles of the persons involved in the use case

  • Preconditions - Conditions which have to be true at the beginning of the use case

  • Basic Flow - Step by step definition of the user actions and the reaction of the system

  • Alternate Flows - Deviations of the basic flow which could come up in the process due to special conditions

  • Exception Flows - Errors that could happen on the way to achieve a goal

  • Post Conditions - Conditions which must be true at the end of the use case

5. Personas

The word personas was first published in 1999 in Alan Cooper’s book: "The Inmates Are Running The Asylum" and is used to describe fictitious types of users. The main reasons for the definition of personas as stated by Alan Cooper are:

  • The product should adapt to the users, and not the users to the product

  • Try to fascinate only some users with the product, it is not possible to make all users happy

In Requirement Engineering it is since then common to define personas, which can be used in the use cases. This are highly personalized users of the software, with a fictitious name and an unique personality.

During the design and implementation phase of software the needs of this fictitious users should be highly considered.

The number of personas should be as small as possible.

The definition of a persona might include the following information:

  • Name and surname

  • Foto

  • Role

  • Marital status

  • Age

  • Goals

  • Education

  • Hobbys

  • Expectations

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