AND and NAND Searches
AND is a logic operation whose output is true when all of its inputs are true. When followed by NOT the result is NAND, its logical complement.
Applications to IR
An AND operation can be applied to information retrieval problems (1 - 3). In most search engines, including Minerazzi, this is the default search mode, which no need to be declared. Thus, the query
w1 w2 w3(1)
is interpreted by Minerazzi like this
AND:w1 w2 w3(2)
and returns documents matching all the terms specified in the query, in any order or proximity. The following figure illustrates this search.
The colored region represents AND matches and the white regions represent AND nonmatches also known as NAND results. The latter are returned with the query
NAND:w1 w2 w3(3)
NAND can return documents matching some or none of the terms being searched. As explained in our search modes article, we only display the first 30 records from the { } set to discourage retrieval abuses. This is the set of documents matching none of the search terms.
Applications
Since AND returns documents matching all of the search terms, it is a search for terms that co-occur. For instance, a search like [ digital agency conference ] returns documents where digital and agency and conference co-occur, in any order or proximity.
Because of its nature, AND searches tend to retrieve documents relevant to all of the terms specified in a query. Thus, adding terms to a query tends to narrow down the search results.
Final Remarks
Minerazzi supports the AND search mode and its complement. This mode helps users to narrow their searches. Because of its nature, it can return many irrelevant results.
References
- Australasian Legal Information Institute (Accessed on 1-1-2014). Search Operators Chart.
- University of Reading (Accessed on 1-1-2014). Search Techniques.
- Case Western Reserve University, Harris Library (Accessed on 1-1-2014). Harris Library Boolean Logic Tutorial.