Teaching:TUW - UE InfoVis WS 2005/06 - Gruppe G8 - Aufgabe 1 - Consistency
Consistency describes a harmonious uniformity or agreement among things or parts.
Agreement or harmony of all parts of a complex thing among themselves, or of the same thing with itself at different times.
Consistency, system design, webdesign
"Consistency (in Design)" is often referred to as the central criteria for successful user interaction. Any interface wants to keep its user focused, and additionally guide him to a procedure or structure. All this needs a clear and consistent framework of elements within the design of the interface. Consistency can create a distinct sense of "place" and makes parts and functions in a system memorable [Lynch and Horton, 2002].
Therefor I want to give a brief overview on the important issues of consistency.
Consistency and its Context
The following list tries to give a ranking that indicates which elements of an interface require consistency the most [Bruce Tognazzini, 2003].
- Interpretation of user behavior, e. g., shortcut keys maintain their meanings.
- Invisible structures.
- Small visible structures.
- The overall "look" of a single application or service-splash screens, design elements.
- A suite of products.
- In-house consistency.
It is a common error to assume that the list should be in reverse order, providing interfaces which look similar on the outside, but have a completely different behaviour on the inside. This would lead to major difficulties in usage, and thus endanger the success of the system. [Bruce Tognazzini, 2003]
Examples: Shortcut Rules
Due to enormous amounts of time spent working with their computers, users are becoming more and more familiar with shortcut keys to save time. The user does not respond to the feedback provided via screen and has to follow and reposition the mouse-pointer to push a button or close a window any more, but relies on the concept that several special key combinations are inherent of a very powerful set of commands which covers most of the functionality provided by the mouse. Users tend to enter most of the commands via keyboard whereas to the right (or left) the mouse gets more and more useless.
It has to be mentioned, that the peploe who are talked about here are not the simple internet surfers but programmers and other groups of skilled users whos aim is to use their computers in the most efficient way.
This way of working would be very efficient if there where not those small inconsistencies which result in some cases in pretty annoying computer behavior. The major problem is that advanced users enter commands in way and a speed which makes it impossible to check whether the computer is reacting in the right way - they just have to rely in the system, and if the commands are not interpreted as usual it is very inefficient to learn this special programs peculiar characteristics.
There are several inconsistencies concerning this problem in the MS Windows and MS Office software packets:
Example: Incomplete Shortcut Definition
To give an example for the points mentioned in the list above, I want to refer to Microsoft Windows and its applications as a suite of products (list element 5).
As you can see this gives the impression that the way of treating commands always swings that way. Unfortunatly this is not the case. The next screenshot shows that there are parts of the software where the shortcut rule is violated. This contradicts rule number 5 of the list above.
[The Microsoft Coorporation, 2003]
This inconsistency leads to a big gap between what the system provides and what the user expects.
Example: The Microsoft Word CTRL+Tab problem
The well known shortcut ALT+Tab which switches between the main windows on a user’s desktop has a "little brother" the CTRL+Tab combination, which switches between the single documents in a MDI (Multiple Document Interface) application. The whole application suite of Microsoft supporting MDI from MS Excel to MS Developer Studio and so on supports this command, whereas MS Word does interpret it in it's own way. It just ignores that the user has pressed the CTRL button and writes a "tab" into the document which is pretty annoying because data may be overwritten. A user working with more than one MS Word document at a time expects the next document to appear but instead of this the currently selected part of the document no matter how many pages it contains is being changed to a single tab.
Although we all are happy about the undo feature, it is tiresome to undo this step and to change the active document manually by mouse.
Example: The undo/save incompatibility of MS Excel
A different problem is the undo - save incompatibility of MS Excel: Everyone is used to be able to undo at least the last modifications he made with his documents. Further everyone has learned that it is very useful to save his documents frequently to avoid data loss due to system breakdowns. As already mentioned advanced users do not think about what to do to save a document or do something else, they just think about saving and automatically press the CTRL+S combination. On the other hand no one cares about deleting or modifying major parts of his/her current work because since many years the undo - possibility has been omnipresent.
The problem occurs in MS Excel and MS PowerPoint if the user relies in both features: If parts of the current document are modified in a way that they cannot be reconstructed without pressing undo and the user saves the document, it is not possible to get back the original data because during saving the undo-history is obviously being deleted.
This wouldn't be a major problem if all programs were working this way, because everyone would assume this behavior. The fact that only some products are reacting this way may cause unwanted data loss just because of inconsistencies which may be avoided very easily.
Example: Same Appearance, Different Meaning
Another but in this case minor inconsistency is the fact that the printer function in all MS Office products reacts in different ways although the icon looks 100% the same:
This is only a minor problem but it often causes unwanted paper output just because the user did not think about using the print function in from the menu instead of pushing the toolbar button. This problem would not appear if both icons would react in the same way. The user would get used to the functionality and it would never happen that he starts the print job without having defined which paper or printer to use.
In the context of invisible structures I would like to come up with an example from the field of webdesign. This field is highly dependent on the principles of design, especially consistency, because it has so much freedom in the lookalike of its products.
Engaging in webdesign you will face a tremendous freedom, which also comes along with a great amount of responsibility.
The structural concept above gives an idea how consistency is practically applied. Providing a graphical and logical concept helps the user to remember and assume where he finds the desired information or service inside the system or website. [Lynch and Horton, 2002]
An example for a good concept is the header shown above. It was part of the website http://www.bridgeman.co.uk . One can easily recognize that the design of the website is consistent in its typography and lookalike throughout the buttons and page banners [Lynch and Horton, 2002]
To sum up it is to say that consistency is a very important topic in design as a whole, and information design in particular.Knowing your users and providing them with a well structured, logically correct and predictable system is the major aim related to the principle of consistency.
[Tognazzini, 2003] Bruce Tognazzi,
First Principles of Interaction Design, Nielsen Norman Group, Created at: 2003. Retrieved at: October 22, 2005
[Hyperdictionary.com, 2005] Hyperdictionary.com,
Consistency. Retrieved at: October 22, 2005
[Whatdowordsmean.com, 2005] Whatwordsmean.com,
Consistency. Retrieved at: October 22, 2005
[Lynch and Horton, 2002] Lynch and Horton,
Webstyleguide 2nd edition. Created at: 2002. Retrieved at: October 22, 2005
[McClurg-Genevese, 2005] Joshua David McClurg-Genevese,
Design in Theory and Practice, Created at: August 15, 2005. Retrieved at: 24. October, 2005