The neighbors of a document are those documents in the database that are the most similar to it. The similarity between documents is measured by the words they have in common with some adjustment for document lengths. In order to carry out such a program one must first define what a word is. For us a word is basically an unbroken string of letters and numerals with at least one letter of the alphabet in it.
Words end at hyphens, spaces, newlines, and punctuation.
Next a limited amount of stemming of words is done but no thesaurus is used in processing. Words from the abstract of a document are classified as text words. Words from titles are also classified as text words, but words from titles also appear a second time with a special added marker designating them as title words. MeSH terms are placed in a third category and a MeSH term with a subheading qualifier is entered twice, once without the qualifier and once with it. No other fields such as author or journal enter into the calculations.