The best IAs work with multiple departments, holding together a unified vision of what the site will entail. Think of them as analogous to a city planner, or even a traditional architect. They will have an overarching vision for how things will work, but they cannot specify too much without exiting their area of expertise. [...] To understand how an IA affects a project, you might imagine assigning a traditional architect to a building after it’s constructed. It’s a laughable proposition, and yet it happens to this day. Even after the most well-engineered buildings are constructed they are still prone to change. [...] Again, as preposterous as it sounds, we typically place today’s Information Architects in a similar position—assigning them to web sites after some other self-imposed IA has prototyped the site. That’s because most people don’t know any better. The sooner you assign the vision of the project to a professional, the faster it will embody that vision. [...] With all of that said, in most projects a dedicated IA is simply not necessary. This is because an Information Architect fills roles similar– but not identical- to that of the project manager. A professional IA is only necessary if your site deals with large amounts of data, especially in an unusual way. Perhaps your site involves a new way to search for books, for example?