"search engine capabilities"

returns only documents that contain this exact phrase. The WAIS search engine performs a literal search exactly as if you had used the boolean operator ADJ. Thus the above example would yield the same results as

  search ADJ engine ADJ capabilities

For this reason, it is best to stick to noun phrases when using literals; if your literal phrase includes stopwords, the stopwords will be ignored.

AND, &&

The AND operator is helpful in restricting a search when a particular pair or larger group of terms is known. For instance, when searching for documents on the weather in Boston, a question such as "weather AND Boston" would return only those documents that contain both the word "weather" and the word "Boston". You can use more than one AND in a query, e.g. "weather AND Boston AND November". Note that the C-like double ampersand (&&) may be used instead of spelling out the word AND.

OR, ||

The OR operator is often used to join two different phrases of a Boolean search. A question such as "hurricane OR tornado" would search for all documents containing either the word "hurricane", or the word "tornado", or both. You can also use more than one OR in a query. A natural language question is much like having an implicit OR between the words, except that the search engine does more work in a natural language query to determine the relevance of words and their relationships in a phrase. Note that the C-like double vertical bars (||) may be used instead of spelling out the word OR.

NOT

NOT is a binary operator. That is, it has to come between two or more words or parenthesized clauses. NOT is used to reject any documents that contain certain words. The question "basketball NOT college" would find all documents containing the word "basketball", that do not also contain the word "college". Note, however, that this question would eliminate articles on any professional players that mention their alma maters; in other words, be careful not to limit your search too much with the NOT operator, make sure that you know what you're throwing away.

Don't be afraid to use NOT! One good search strategy is to search for a broadly occurring term and get lots of documents you don't want, and then to use NOT to filter out the bad documents. For example, if you're trying to cook okra, you might search for "cooking AND okra" and find nothing; but if you search for "cooking", you find lots of articles on cooking meats and pastas. You then can search for "cooking NOT meat NOT pasta", and you might find more interesting articles that eventually lead you to your goal. Another handy trick is to use NOT to "break the 40 barrier". Typical WAIS clients only display 40 documents, but if you use NOT wisely, you can flush out the documents you don't like in those 40 and progressively refine your search, adding better and better documents to the 40 that you see.

ADJ

The adjacent operator, ADJ, is used to ensure that one word is followed by another in the returned document, with no other words in between. For example, "cordless ADJ telephone" returns only documents containing "cordless telephone" and ignores documents that only contain one of the words or that contain both but not adjacent to one another. ADJ will nonetheless work when stopwords interrupt two words; for example, the preceding example will find occurrences of "cordless for telephone". Note that the ADJ operator yields the same results as does a literal query. Also note that ADJ, unlike AND, OR, and NOT, is not a commutative property - "telephone ADJ cordless" does not work the same as "cordless ADJ telephone".

Mixing Natural Language, Literals, And Booleans

The mail-or-email parse format is an example of a parse format in which fields are tagged. For this parse format, the WAIS parser detects the "to" and "cc" fields, the "from" and "sender" fields, the "subject" field, and the "date" field. An example of a question using natural language, a boolean operator, and fielded search is: "company picnic AND from=barbara". The WAIS server would then find email messages about a company picnic that Barbara sent.

  field-name    comparison-operator    value

where comparison-operator may be one of > (greater than), < (less than), >= (greater than or equal to), <= (less than or equal to), or = (equal to).

Currently, dates with the following formats are supported:

              m-d-yy    m-d-yyyy    mm-dd-yy 
              m/d/yy    mm/dd/yy    m.d.yy 
              today     yesterday

Only positive integers are supported for numeric fields. If the comparison operator is =, then the range may be specified using the word TO, as in

           date = 4/15/93 TO 4/14/94

Both ends of the range are inclusively specified.

A document receives a higher score if the words in the question are in the headline, if the words appear many times, or if phrases occur as they do in the question. A document's score is derived using techniques such as word weighting, term weighting, proximity relationships, and word density. These scoring techniques are outlined below.