Conceptual Model — Need and Requirements

Design becomes successful and well received when the end user is kept in mind while designing the product/service. We have seen time and again that great products are almost always simple, use a small learning curve and utilize knowledge in the world to their advantage.This article is about why conceptual models are necessary and how good conceptual models can help create time tested design.

A great success story is the Graphical User Interface designed at PARC. The invention of the GUI made interaction extremely easy compared to the character/vector based predecessors . In the book ‘Bringing Design to Software’, Terry Winograd talks about why the Palo Alto Research Center was set up and how the worlds first GUI was proposed and designed. The STAR program was conceived with the idea to put a computer in every household.

The Xerox Star GUI

The team came up with a design that has stuck around in the industry for decades. Analyzing the reasons for success, we realize that they has a strong understanding of the user’s conceptual model. The usage of a bitmap display screen to visually show the operations taking place, the WYSIWYG(What you see is what you get) design style and having a set of commands to perform common tasks are brilliant design thoughts. Users are able to manipulate tasks and immediately receive feedback on what is achieved. The best part was common commands would work the same way uniformly.

David Liddle’s team studied about methods to design user interfaces and proposed that good control mechanism, a way to let the user perform and manupulate tasks with a visual feedback system- how users see things along with a solid understanding of user’s conceptual model — the way a user thinks and would most likely respond would be the ideal design route to take. The STAR has followed this design style and even today most of the computers work based on this design style.

A good approach in design is to understand what user requires and would like use as features in the product. Centering design based on end user would help have direction with regards to functionality and design style. In the book Interaction Design: Beyond Human-Computer Interaction, Yvonne Rogers’ team suggests about analyzing the needs of the user and then transforming these needs into requirements specs. Gathering and analyzing data in the right manner is essential to understand what users want. Data can be gathered using questionnaires, user interviews, process walk throughs. Usecases are also extremely helpful as they help break tasks and keep design focused on what users want.

The STAR GUI is a great example of how design can change the way the world works. Its essential to keep users in mind and understand how they react in various situations.


Terry Winograd, The Alto and the Star, in Winograd, T., Gordon, P., eds, Bringing Design to Software, New York: Pearson, 1996.

David Liddle, Design of the Conceptual Model, in Winograd, T., Gordon, P., eds, Bringing Design to Software, New York: Pearson, 1996.

Yvonne Rogers, Helen Sharp, Jenny Preece (RSP), Interaction Design: Beyond Human-Computer Interaction, 3rd ed, Wiley. 2007, Chapter 10, Identifying needs and establishing requirements.

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