The Mystery of the Search Engine

The Mystery of the Search Engine

Today's computers can search through large amounts of data in less than a second. The downside of this is that oftentimes a search query returns lots of information that we don't want.

Consider the search engine below, which quickly checks all of Sir Arthur Conan Doyle's works about Sherlock Holmes. It returns each Holmes short story or novel chapter that includes the search term, as well as the first time the term is mentioned for three of the documents.

If you're trying to find a part of a story where Mark takes a train, you might try searching for the train:

This isn't very helpful since trains are a common occurrence in these stories — the search engine returns 46 results. Fortunately, there are a couple ways that we can make search results more relevant.

If you are looking for a full phrase rather than a single word, search engines can match phrases by including the phrase in quotes. If you remember that the story you're looking for has Sherlock taking a train to Newhaven, you might search for "train to Newhaven":

revealing that you were looking for an event in The Adventure of the Final Problem. The drawback of using quotes, however, is that you'd need to remember the exact phrasing.

If you aren't blessed with such a memory, you can also use logical operators. The search term train AND Newhaven would also have done the trick — AND signifies to only return results with both the search terms train and Newhaven.

train AND Newhaven

The Adventure of the Final Problem

…

es had indicated, the less so as it was the only one in the 

train

 which was marked "Engaged." My only source of anxiety now was the son-appe

…

1 matching document

AND isn't the only logical operator we can use in the search. We can also use OR to return results with either of the search terms — and NOT, to exclude results that include the term that follows. These logical operators can be combined using parentheses as needed.

As an example, if we wanted to find instances of the word train where it didn't refer to an actual physical train, we might search for train AND NOT (station OR catch). This query finds uses of the word train without mention of a station or "catching the train":

train AND NOT (station OR catch)

The Adventure of the Resident Patient

…

d played is not sufficiently accentuated, and yet the whole 

train

 of circumstances is so remarkable that I cannot bring myself to omit it ent

…

The Adventure of the Devil's Foot

…

 theory of a poison which worked by combustion. "With this 

train

 of reasoning in my head, I naturally looked about in Mortimer Tregennis's room

…

The Disappearance of Lady Frances Carfax

…

I should be obliged to you if you would indicate it." "The 

train

 of reasoning is not very obscure, Watson," said Holmes with a mischievous t

…

1-3 of 9 matching documents

We see that this does find us some examples using the train more metaphorically, with mentions of trains of circumstances or reasoning.

With a cleverly designed search query, you can find the information you're looking for much more quickly than using a broad search term and parsing through the results manually.