SEO by the Sea points to an interesting patent that describes how Google Sets works. Google Sets is one of the first services that were added to Google Labs and it's a cool way to find list of related terms. Google Sets is a tool that generates lists from a small number of examples by using the web as a big pool of data. You enter some items and Google Sets finds other items that tend to co-occur frequently with your examples. For example, you could enter Barack Obama, Hillary Clinton, Rudy Giuliani and get a list of US presidential candidates.
One particular type of information often present on the web includes lists, such as lists of restaurants, lists of automobiles, lists of names, etc. Lists may be identified in a number of different ways. For example, a list may include an ordered list or unordered list. Special tags in a HyperText Markup Language (HTML) document identify the presence of ordered and unordered lists. An ordered list commences with an <OL> tag; whereas an unordered list commences with an <UL> tag. Each item in an ordered or unordered list is preceded by an <LI> tag.
Another type of list may include a definition list. A special tag in a HTML document identifies the presence of a definition list. A definition list commences with a <DL> tag. Each item in a definition list is preceded by a <DT> tag. Yet another type of list may include document headers. Special tags in a HTML document identifies headers using <H1> through <H6> tags. Other types of lists may be presented in yet other ways. For example, a list may be presented as items in a table or as items separated by commas or tabs.
After identifying lists on the web, Google generates a probabilistic model from the examples provided by users and classifies the lists according to the model. The items are assigned weights based on the classified lists and the weights are added to form a list based on the total weights.
