Complex concepts are intrinsic to the way people think.
A concept may be represented to a person by a single word, but in fact contains assumptions about the building blocks that concept is made of and the relationship of that concept to a framework of knowledge. An effective search engine should allow users to represent a specific concept by a single word, to build up more complex concepts from simpler ones, and to assign a concept to a position in an existing framework. In many cases, searching within a particular informational context is more important than searching a particular company's or individual's information. However, there are many possible frameworks that can provide context. A good search scheme should provide an extensible set of frameworks with mechanisms to assign information-containing sites to positions in the frameworks.