15.2. Fast and Slow Layers
In his book The Clock of the Long Now, Stewart Brand introduces the notion that society is a construct of several layers, each with a unique and suitable rate of change (Figure 15-2). The slow layers provide stability; the fast layers drive innovation. The independence of speed between layers is a natural and healthy result of societal evolution. Imagine the alternative. How about commerce moving at the pace of federal bureaucracy? Remember the Soviet Union?
Figure 15-2. Societal layers
This recognition of independently dynamic layers holds great promise within the narrower domain of information architecture. By isolating enduring IA from adaptive IA, we can invest sensibly in long-term infrastructure while creating flexibility where it's needed. Figure 15-3 is an early attempt to identify these layers.
Figure 15-3. Information architecture layers
The lowest and slowest layers are facets and their hierarchies. These constitute the foundation of the enterprise IA infrastructure.
Next, the embedded navigation system composed of browsable taxonomies, indexes, and the search system defines at a fundamental level how users are able to search and browse. These two bottom layers should be stable. They become intertwined with content, technology, and process, and become the core to users' mental models. Change at the bottom is painful and expensive. You also don't want to frequently switch enabling technologies such as content management systems, search engines, and portal software, as they too become enmeshed with content and process.
Moving to the faster layers, controlled vocabulary terms will evolve with product and service offerings and with the broader language of business and technology. Adaptive finding tools such as project-specific guides, indexes, and collaborative filtering devices will benefit from continuous adaptation. And, finally, the site's content and services may change on a regular basis, along with tweaks to the user interface.