Block 3 Blog 4 - Design Principles

Lidwell at al's 5 categories

1. How can I influence the way a design is perceived?
2. How can I help people learn from a design?
3. How can I enhance the usability of a design?
4. How can I increase the appeal of a design?
5. How can I make better design decisions?


80/20 rule

The 80/20 rule is a princible of design that basically says that 80 percent of the effects of a system are caused by 20 percent of it's variables.

Example

An example of this is a web browser, there are many things you can do in a web browser. A lot of people do not know about most of these things, but the main things that users need are shown in the toolbars at the top, such going back, forward or typing in a URL. These functions represent 20% of the available functions, while there actions represent 80% of he things a user would want or need o do.

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Affordance

Affordance is related to what something is designed to do. One of the examples given talks about door handles. A flat plate is used for pushing and a handle is used for pulling. A door that does this has a better affordance than a door that uses a handle for pushing and pulling.

Example

Laptops afford mobility. Most laptops, especially newer laptops are made so that they can be easilt tranported to other places, and carried with you. So you can work on the go, easily.


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Constraint

A constraint is something that limits what a system can perform. The two basic types of constraints are physical and psychological constraints. Physical constraints control where or how something or part of something can move, while a psychological constraint is something that limits the amount of things people can do by thinking about how people would already perceive things. So this links directly to symbols, mappings and conventions.

Example

One form of a physical constraint would be a wire. I two things are connected by a wire, users know that the two devices could not be used together if the wire was taken away, such as a mouse and computer. The mouse has to stay within a certain distance of the computer for it to work properly.
An example of a pyschological constraint would be a so not disturn sign. This doesn't stop people from doing anything, but if people were to see it outside of an exam hall, they would know they need to keep quiet for obvious reasons.

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Cost-Benefit

The cost-benefit princible talks about only persuing something if it's benefits are equal or greater to it's cost. Basically, if something costs a lot, but isn't very beneficial or useful it has a poor design. If something has a low cost and is beneficial it has a good design. Systems doesn't always have to have a low cost to have a good design though. If something is vital to a system you it wouldn't matter as much if it was expensive. Cost isn't always related to money either, it also includes factors such as effort.

Example

An example of this is the lock switch on the bottom of an iPod. The switch is small not easy to use without tipping the iPod and looking at it. But if you keep your iPod in a small pocket, or somewhere buttons might be pressed accidentally, it stops songs or settings from being changed, which makes it a good design.

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Errors

Errors are things that can go wrong in a system, or performing an action and getting thw wrong result. These usually happen because of human error, but these human errors are usually caused by a design error. Errors can be kept by giving as much feedback as possible, or using things such as confirmation screens.

Systems can also help problems with errors by enabling people to undo errors easily.

Example

Flash Actionscript error, or errors that occur when using any programming or scripting language. When you try to run a program, whatever program you are using, two different things can occur. The prgram either runs, or you are given an error message. The error message usually contains what went wrong. But sometimes the message is hard to understand.

This is good and bad, for someone who is used to using the program, it provides good feedback about what they need to do. For someone who is not familiar with a program it can be confusing and frustraing. Especially if they think everything was alright.

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Five Hat Racks

Five Hat Racks states that there are five ways to organise information. By Category, time, location, alphabet and continuum.

The five hat racks princible states that there is a limited number of ways to organise information, regardless of the application.

Example

An example of this could be for computers. Information about them could be ordered by;
Category - what type of computers they are(laptop, desktop)
Time - How old the computers are, when they were manufactured
Location - Where you are buying them from
Alphabet - All computers sorted alphabetically
Continuum - This could be used for many different things, including price, RAM and many other specifications of computers.

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Normans Principles
(Visibility, Feedback, Constraints, Mapping, Consistency, Affordance.

The 80/20 Rule links to Visibility and Mapping, since the rule is mostly related to since this rule is about users being able to see the things most. It is related to visibility because these things should be the most visible, and mappings because that is related to where these things will be placed.

Affordance and Constraints are already part of Normans Principles as well. Affordance and constraints can also easily be linked with each other.

Cost-Benefit can be related to mapping and consistency because if functions on a device are placed in poor positions, or an option does not follow the general pattern of everything else within a device then these things may become more of a problem to use than a benefit.

Errors can be linked with all of the principles. Poor visibility, and not being able to see the right things can lead to errors.
Feedback needs to be given when errors occur, and feedback can also prevent errors from occuring in the first place, by explaining what certain functions do.
Constraints can stop users from performing actions that could lead to errors.
Good mapping could also prevent errors while poor mapping could lead to a higher number of errors.
If a device is not consistent errors can easily be made, for example, if two things look like they work in the same way, but don't, errors can easily occur.
If deviceslook like they are used for things which they are not supposed to be used for, they would have a bad affordance. This could also lead to many errors.

Five Hat Racks is related to visibility and feedback because it is related to how people see things, and what they see after selecting certain options.