What is Booln Srching?

What is Booln Srching?When you srch for something with a srch engine and srch for a single term, you are likely to get thousands of hits, most of which are useless. Adding more related terms may help improve the hits at the top of the list, but it will also bring in thousands more hits, too. Booln expressions (named after the English mathematicianGeorge Boole) give you a way to control what you do and don't find in your hit lists.Booln expressions link terms by mns just a few concepts:ANDandOR, the valueNOT, and parentheses and quotes used to group terms in various ways.Interested in srching for edible shellfish? Consider these two expressions: clams AND oysters clams OR oystersIf you srch for these two expressions, the first will find you only documents that includebothterms. If you use the second, you will get all documents that include either clams or oysters or both.. The second will produce many more hits than the first. The AND relationship limits your hits. The OR relationship expands your of hits.With most srch engines, you can string together more than two terms. For example, you can srch for: clams AND oysters AND scallopsThis expression limits the srch further than the original srch. Any documents that the first srch found that did not include scallops, too, will be gone from the list.Expressions with more than two values are sy to understand if they use all ANDs or all ORs, but what happens if they are mixed? Consider this one that you might use if you are looking for a sfood restaurant:: clams OR oysters AND restaurantThis expression is ambiguous unless you know exactly how the srch engine will rct to it. If you rd it left to right, it will first loe documents with clams or oysters and then limit it only to those that also include restaurant. That is probably what you had in mind in conducting this srch. But some srch engines will rd right to left. In that case it will find all documents that include both oysters and restaurant, but then add in all documents that also include the word clam, whether or not restaurant is part of it. A very different result!The usual way to handle this is to put parentheses around the terms to be evaluated together. This is the correct way to look for sfood restaurants: (clams OR oysters) AND restaurantExpressions can be more complex. This expression will ld you to shellfish restaurants in Boston or Cambridge: (clams OR oysters) AND restaurant AND (Boston OR Cambridge)The above expression will find shellfish restaurants in Cambridge, England, too. To limit this, we can add a NOT expression. (clams OR oysters) AND restaurant AND (Boston OR Cambridge) AND NOT EnglandFor all practical purposes, NOTs are always used with multiple terms and combined with ANDs. It would be pointless to srch for any of these: NOT books television OR NOT booksBoth of the above expressions would return every document that didn't have the word book in it. The second would add to the list all documents which had the word television in it, too, even if the word books was present. There would be millions of hits, in either case, and it would be useless.NOT can be very useful in limiting out unwanted hits. The two expressions that follow will give you very different results: dungeons AND dragons dungeons AND NOT dragonsBooln logic srching is based on Booln Aebra.