Document retrieval is defined as the matching of some stated user query against a set of free-text records.
Text retrieval is a critical area of study today, since it is the fundamental basis of all internet search engines.
Form based document retrieval addresses the exact syntactic properties of a text, comparable to substring matching in string searches.
The text is generally unstructured and not necessarily in a natural language, the system could for example be used to process large sets of chemical representations in molecular biology.
The PubMed[1] form interface features the "related articles" search which works through a comparison of words from the documents' title, abstract, and MeSH terms using a word-weighted algorithm.