Text database systems

A text database system, often called an information retrieval system, is designed to process a text model of the data, viewed as an ordered sequence of documents, paragraphs, sentences, words (i.e., as a list structure). Although relations are sets of tuples, and therefore unordered, the relational model can still be used successfully for text, but surprisingly it is shown that at the physical level the two apparently different approaches are likely to be identical. However, since the human view of text is much closer to a list than to a relation, the text model is more appropriate for document handling. In addition, when tuples include a large amount of free text (as in the "soft" sciences), and when queries involve text processing more often than the eight operations of relational algebra, then also the text model is more appropriate.