A follow up to uncontrolled vocabulary.
Many of the more advanced search engines try to improve relevance by extracting meaning out of the content of documents, i.e. without any input required from users. This is commonly known as auto-classification (or auto-categorisation). It then enables you to perform faceted search queries (also known as conceptual search). For example, if you search on ‘politics’, the results might include facets for different political parties (Democrats, Republicans), politicians (Bush, Clinton, McCain, Obama), government activities (budget, new policies) and so on. It’s an effective way of quickly narrowing down your search criteria and hence refining results.
The challenge is can you trust the data? How accurate is the content within your documents? For example, let’s look at the number 35.
That’s the average number of people wrongly declared dead every day in the US as a result of data input errors by social security staff. Doh! 🙂 (Source: MSNBC. Published in NewScientist magazine, 8 March 2008)