How do you use functional, behavioral, and structural requirements analysis techniques?

1 Functional requirements

Functional requirements describe what the software system should do, such as features, functions, inputs, outputs, and interactions. These requirements detail the business logic, data processing, calculations, and validations that the software system should perform. For example, users should be able to register, login, and update their profiles; invoices and reports should be generated based on user data; notifications and alerts should be sent to users via email or SMS. To elicit and document functional requirements, you can use techniques such as use cases, user stories, and data flow diagrams. Use cases involve a scenario of a user interacting with the software system to achieve a goal. A user story is a short statement expressing the user's need or desire from the software system. Data flow diagrams illustrate how data flows through the software system.

2 Behavioral requirements

Behavioral requirements are used to describe how a software system should behave in terms of states, events, actions, and reactions. They focus on the dynamic aspects of the software system such as how it responds to user inputs, external stimuli, or internal changes. For example, software systems should display an error message when invalid data is entered; switch to offline mode when the network connection is lost; and encrypt and decrypt data before storing and retrieving it. To elicit and document behavioral requirements, techniques such as state diagrams, sequence diagrams, and activity diagrams can be used. State diagrams are graphical representations of the states and transitions of the software system or its components. Sequence diagrams show the sequence of messages that are exchanged between the software system and its actors or components over time. Activity diagrams are graphical representations of the activities and flows of the software system or its components.

3 Structural requirements

Structural requirements describe how the software system should be structured, in terms of components, relationships, interfaces, and constraints. They specify the static aspects of the software system, such as its organization, composition, integration, and configuration. For example, a software system may need to consist of three layers - presentation, business, and data - and communicate with other systems via RESTful APIs while complying with security and performance standards. To elicit and document these structural requirements, you can use techniques such as class diagrams for representing classes and their attributes/methods; component diagrams for representing components and their interfaces/ports; or deployment diagrams for representing nodes and their artifacts/executables.

4 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?