When it comes to searching, most people have a Google or Bing mentality. This means they have been inadvertently trained in search behavior because of their extensive usage of these search tools. They are used to typing in a word or two and have the results come back in a ranked order. This type of search is a course grained search. It is effective when you are blindly reaching out trying to find a match. Users then look at the results and narrow down their search manually by checking the results to see if it was what they were after.
This type of searching is very effective when the information is spread across a large number of systems. It is not effective when more refined or fine grain search methods are requested. These search systems are also based around the concept of HTML page being the only type of digital object being searched on.
A number of these search engines struggle or just cannot handle fine grained queries. If a user wanted to find all images that were portrait...