13 equilibrium order time

www.dadda.it roberto@dadda.it Excellence in usability 1st semester 2021-2022 1
ERGONOMICS APPLIED TO THE DESIGN OF USABLE WEB
PAGES AND APPS
Roberto DADDA and Paolo NEGRI

Order, equilibrium and time.

Order

Disorder gives the idea of complexity

Las Meninas (Velázquez)
https://en.wikipedia.org/wiki/Las_Meninas
Brain always search for rules

Rules change perseption

Pablo Ruiz Picasso (25 October 1881 – 8 April 1973)
In all the formats, rules are related to concepts

D. De Kerckove, Brainframes, Technology, mind and business, tr. it. a cura di B. Bassi,
Brainframes. Mente, tecnologia, mercato, Bologna, Baskerville, 1993
Ascending and descending
http://www.kainos.it/numero2/sezioni/ricerche/cuomo01.html#piede52
In latin alphabets writing and reading community
up down

Jacob’s Ladder

IBM, Systems Application Architecture: Common User Access:
Panel Design and User Interaction, Document SC26-4351-0, 1987.
IBM Common User Access (CUA) 1987

• All operations could be done with either the mouse or the keyboard;
• Menus are activated/deactivated with the F10 key;
• Menus are opened by pressing the Alt key plus the underlined letter of the menu name;
• Menu commands that require parameters to proceed are suffixed with an ellipsis ("…");
• Options are requested using secondary windows (often called dialog boxes);
• Options are divided into sections using notebook tabs;
• Navigation within fields in dialog boxes is by cursor key; navigation between fields is by pressing the Tab ↹ key; ⇧
Shift+Tab ↹ moves backwards;
• Dialog boxes have a 'Cancel' button, activated by pressing the Esc key, which discards changes, and an 'OK' button,
activated by pressing Return, which accepts changes;
• Applications have online help accessed by a Help menu, which is the last option on the menu bar; context sensitive
help can be summoned by F1;
• The first menu is to be called 'File' and contains operations for handling files (new, open, save, save as) as well as
quitting the program; the next menu 'Edit' has commands for undo, redo, cut, copy, delete, paste commands;
• The Cut command is ⇧ Shift+Del; Copy is Ctrl+Ins; Paste is ⇧ Shift+Ins;
• The size of a window can be changed by dragging one of the 8 segments of the border.
CUA IBM

1975, 1978

In WordPerfect, the command to open a file
was F7, 3.
In Lotus 1-2-3, a file was opened with / (to
open the menus), F (for File), R (for
Retrieve).
In Microsoft Word, a file was opened with
Esc (to open the menus), T (for Transfer), L
(for Load).
In WordStar, it was D.
In emacs, a file is opened with Ctrl+x
followed by Ctrl+f (for find-file).
Wikipedia
At the beginning was caos!
Word processing, open a file.

Page splitting, a critical decision

Information density
If density is too low
Unused precious space
Longer access time
If density is too hi
hight cognitive load
possible errors
difficult to concetrate what is important
Useful information
Total information content
Information density =

Menus

Equilibrium

La notte stellata - Vincent Van Gogh - 1889

Resurrezione Piero della Francesca 1450 - 1463

Nascita di Venere – Sandro Botticelli – 1485 1486

Time

The neglected 3° dimension of pages

Response time
Δt

Time ranges
Time (s) Webb/App Cloud based services
0,1
is about the limit for having the user
feel that the system is reacting
instantaneously, meaning that no
special feedback is necessary
Limit for users feeling that they are directly
manipulating objects in the UI.
1
is about the limit for the user's flow
of thought to stay uninterrupted,
even though the user will notice the
delay.
Limit for users feeling that they are freely
navigating the command space without having to
unduly wait for the computer.
10
is about the limit for keeping the
user's attention focused on the
dialogue.
Limit for users keeping their attention on the task.
Anything slower than 10 seconds needs a percent-
done indicator as well as a clearly signposted way
for the user to interrupt the operation.
Extract from http://www.nngroup.com/articles/response-times-3-important-limits/

Placebos for anxiety

If possible progress indicators
But without cheating:
If do not know just tell!

Give signs…

Learn from movies

Scena changes in film editing
Principles:
• Easy correlation
• Fluidity

Easy correlation
In scena transition
must be easy for the
viewer understand the
correct corelatiion
between situations.
This is done:
• Keeping objects position
• Keeping relative
orientation
• Keeping motion directions

Position

Animations
Helps to understand
and «feel» what
hapens.
Sound is usefull
MAC OS7

Scrolling vs paging

Usability
Roberto DADDA
roberto@dadda.it
www.dadda.it
Skype, Facebook e Twitter robertodadda

13 equilibrium order time

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