Human-Computer Interaction & Usability Engineering

Prototyping & Visualisation Techniques

Introduction

A dictionary definition of prototype is:

“prototype n - an early model of a product, which is tested so that the design can be changed if necessary”.

This definition hold true for some professionals e.g. engineers. In engineering a fully functional version of the product - a prototype - is created. However, for designers of user interfaces, a prototype need only be as functional (or complete) as the designer requires. The designer may chose to create a subset of the system a) to save time and b) because it may be that only one concept of the system needs tested - not the whole thing.

There are three ways for the designer to construct the prototype:
Full prototype - this may be fully functional, but it will provide less performance than the final system.
Horizontal prototype - this may display the full range of the system (menus, dialogues, etc.), but it doesn’t go into any one area in depth.
Vertical prototype - this may be fully functional for only part of the system, but will not necessarily display the range of the system.

A good designer will use a prototype to clarify the ideas behind the design to the user, management and the rest of the design team. This may change their expectations and, consequently, the product requirement.

A prototype does not have a certain lifespan, it may be used then thrown away, or it may eventually evolve into the final product.

Design Strategies

Prototyping occurs as part of a development strategy. Before we look at different prototype methods, we should first understand what the common design strategies in industry are.

Top Down Design
Top down design has prototyping towards the end of the development process, mainly because the requirements for the system are clearly understood. In the early stages, the design is refined before the prototype is produced, and the final stages are carried out iteratively.

Example:
document design
reviews
prototyping
implementation
user testing

Bottom Up Design
Bottom up design has prototyping at the start. This is useful for completely new projects where it is unclear what is required until the users have become involved. The prototype is designed rapidly and iteratively - it’s unlikely the design will be right first time. It is important to combine prototyping and user testing (and be prepared to make changes) to create a well- designed user interface.

Integrated Design
Integrated design is where the prototype is part or the system which is built round a particular design methodology. Both the prototype and the final product are parts of the same environment.

Classes Of Prototyping Techniques

Prototyping techniques can be broken into 3 different classes. These vary by the level of completeness and testability.

Slide Show/Storyboard Techniques
These type of techniques allow designers to turn their thoughts into visual representations which can then evolve into complete design. The designer creates a sequence which can be arranged to display various scenarios. This form of prototyping is good for communication amongst designers and is quick to assemble.

“Wizard Of Oz” Techniques
It may be necessary to test design concepts where the interface technology needed doesn’t exist yet or it is far too expensive. The designer can set things up so that it seems as though the technology is responding to the user.

Example:
Voice recognition - the designer can get a human to pretend to be the computer’s “voice” and to respond to input from the user.

This “Wizard Of Oz” technique (remember the film?) allows the designer to explore concept which would otherwise be out of reach.

Fully Animated Techniques
Having a fully functional prototype is extremely useful. Apart from being an excellent communication tool and a specification for the final product, it can also be used to get the most valuable feedback possible - through user testing and evaluation. Flaws which have been overlooked are revealed and product-specific questions answered. Unlike storyboard and “Wizard Of Oz” techniques however, fully animated techniques can take weeks to complete.

Advantages And Disadvantages Of Prototyping
The benefits of prototyping far outweigh the drawbacks. Testing a prototype of an interface will provide feedback which can help ensure a proper design specification is produced. This can reduce maintenance and training and make it more likely that the user will accept the end product. It also has the advantages that it reduces the cost of the final design (by finding faults at an early stage) and it can be produced very quickly (a prototype should come together in a matter of days rather than weeks or months).

The main disadvantage of prototyping is that the customer looks at it and see a system near completion. They then wonder why on earth it will take months and months to produce a final working system. This would have to be carefully explained to your client. Another disadvantage is that the limitations and constraints of the real system can be ignored in the prototype. This can lead to an unrealistic interface.

On the whole, it is far more beneficial to quickly and cheaply produce and test a prototype than it is to spend time, money and effort correcting errors and making changes when the system has been put in place.

On to the next chapter ... Evaluation and evaluation techniques