External interface requirements 5.1 User interfaces . Including: 5.1.1. References to user interface standards or product line style guides that are to be followed 5.1.2. Standards for fonts, icons, button labels, images, colour schemes, field tabbing sequences, commonly used controls, branding graphics, copyright and privacy notices, and the like 5.1.3. Screen size, layout, or resolution constraints 5.1.4. Standard buttons, functions, or navigation links that will appear on every screen, such as a help button 5.1.5. Shortcut keys 5.1.6. Message display and phrasing conventions 5.1.7. Data validation guidelines (such as input value restrictions and when to validate field contents) 5.1.8. Layout standards to facilitate software localization 5.1.9. Accommodations for users who are visually impaired, colour blind, or have other limitations 5.2 Software interfaces 5.3 Hardware interfaces 6. Quality attributes 6.1 Usability 6.2 Performance 6.3 Security