A mechanism to uniquely identify users and to provide protected access to the device.

Problem

The user needs to provide personalised credentials to log on to a system.

Context

When users need to prove their identity, e.g., when logging on to their terminal for the first time or when changing shifts, a username/password combination is required.

Forces

Proper feedback for misspelled entries must be given when users provide their login details. The time required to log off and on should be minimised.

Solution

Provide a log on screen with two fields, username and password, and an on-screen keyboard to enable the user to type in username and password. This pattern is a composed structure consisting of the following basic patterns and elements:

• The patterns text fields and text editing and virtual keyboard contain a description how to handle text input
• Mandatory and optional fields provides guidelines how to highlight required fields in forms
• If user input is syntactically or semantically wrong, input validation provides a rationale how to display feedback
• Following the guidelines in the blog post how to reduce user error by appropriately sizing controls helps avoiding typos when entering username and password

Usability Impact

Error prevention

Safety Impact

Together with role management, this pattern provides an additional layer of security for the application. Competence and responsibility for the areas under control is clearly assigned.

Usage

This pattern has been used in several European railways projects.

Your opinion!

Feel free to provide your comments, reports of usage of this pattern, or feedback in general!