Design of web maping applications

As you know, the page paradigm in Internet evolved to the application paradigm.
We are now building web 2.0 maping applications, with a lot of functions, a lot of capabilities and, of course, more complexity comparing to the first web maping applications.
I think that one of the key challenge for the future is to be able to propose web applications that are usable.
Maybe I should start with a definition of the term usability. Usually, five terms (see wikipedia) are associated with usability:
- Learnability: How easy it is for users to accomplish basic tasks ?
- Efficiency: Once users have learned the design, how quickly can they perform tasks ?
- Memorability: When users return to the design, how easily can they reetablish proficiency ?
- Errors: How many errors do users ?
- Satisfaction: How pleasant is it to use the design ?

I bet that we all would like that our web maping applications can receive positive answer to all these questions.
The key point is that all these questions are related to the users. So, obviously, we need to know these users. We need to know what are the users expectations, what are the users reactions, how the users perform.
During a project life-cycle, two main things can be done in order to take in account the users. Firstly, before the development phase, user centric design can be conducted in order to get the maximal number of input of the end user (not the GIS expert; the end user. I will come back in other blogs about this). And secondly, after the development phase, usability studies can be conducted in order to verify that the application meet the expectations in term of usability. I got the chance to participate to usability studies and I can only say that they are incredibly informative and valuable.
But let's come back to the users. Of course, users are not all the same. They have different background, culture, knowledge, expertise. Let's imagine that you develop a web mapping applications for touristic information: in this case, the diversity of users is endless. So, is it possible to create a usable web maping application for all these users ? Of course, the answer is yes, and why ? Because, some general rules can apply. My favourite reading in this domain is the book "Universal Principles of Design" from Lidwell, Holden and Butler. The sub title is very explicit: "100 ways to enhance usability. Influence perception, Increase appeal, Make better design decision and Teach through Design".
But, how is this related to MapFish ? MapFish, as web development framework provides the brick to create User Interfaces (OpenLayers controls, GeoExt and MapFish widgets, etc...). This is probably not a bad idea to organize and use these bricks in a usable way.
I'd like now to write a serie of blogs that will present some of these principles. Stay tuned ;-)