NOV, or News Overview, is a widely deployed indexing method for

Usenet Usenet () is a worldwide distributed discussion system available on computers. It was developed from the general-purpose Unix-to-Unix Copy (UUCP) dial-up network architecture. Tom Truscott and Jim Ellis conceived the idea in 1979, and it was ...

articles, also found in some

Internet The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, pub ...

email Electronic mail (email or e-mail) is a method of exchanging messages ("mail") between people using electronic devices. Email was thus conceived as the electronic ( digital) version of, or counterpart to, mail, at a time when "mail" meant ...

implementations. Written in 1992 by

Geoff Collyer Geoff Collyer (born 1958) is a Canadians, Canadian computer scientist. He is the senior author of ''C News'', a protocol-neutral news transport, and the designer of NOV (computers), NOV, the News Overview database (article index) used by all moder ...

, NOV replaced a variety of incompatible indexing schemes used in different client programs, each typically requiring custom modifications to each

news server A news server is a collection of software used to handle Usenet articles. It may also refer to a computer itself which is primarily or solely used for handling Usenet. Access to Usenet is only available through news server providers. Articles and ...

before they could be used. In modern

NNTP The Network News Transfer Protocol (NNTP) is an application protocol used for transporting Usenet news articles (''netnews'') between news servers, and for reading/posting articles by the end user client applications. Brian Kantor of the Univers ...

implementations, NOV is exposed as the and related commands.

Operation

In its original implementation, the header lines of each incoming message are examined, and a single line of text is appended to the overview files, with one overview file present for each

newsgroup A Usenet newsgroup is a repository usually within the Usenet system, for messages posted from users in different locations using the Internet. They are discussion groups and are not devoted to publishing news. Newsgroups are technically distinct ...

. Tab (

ASCII ASCII ( ), abbreviated from American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. Because of ...

code 9) characters and line breaks within the headers are converted to spaces (ASCII code 32), and the header fields within each overview line are then delimited by tab characters. The first seven fields in a NOV line are fixed and unlabeled: #Subject: header contents #From: header contents #Date: header contents #Message-ID: header contents #References: header contents #Size of the article in

octet Octet may refer to: Music * Octet (music), ensemble consisting of eight instruments or voices, or composition written for such an ensemble ** String octet, a piece of music written for eight string instruments *** Octet (Mendelssohn), 1825 compos ...

s #Lines: header contents The header lines are those defined in either RFC 2822 or RFC 1036. If data for any of these fields is missing, a tab alone is put in its place. The value of the size field is approximate, as servers may count line endings as one or two characters. Additionally, the lines value may be calculated by the server, supplied by the message sender, or omitted altogether. An arbitrary number of additional fields may be added to any NOV line. The eighth and later fields must be labeled in the form "Header-Name: contents", again delimited by tabs. The order and presence of additional fields are allowed to vary from line to line, and from server to server. Some server provide a schema of what is recorded to new overview lines in the form of an NNTP command, but this cannot be relied upon to be accurate for older entries. In practice, most servers supply only one optional field, the contents of the Xref: header, to allow crosspost management.

Variations

While virtually all modern news server and newsreader software employs NOV, it has also found its way into other applications such as email clients. One prominent example is

Gnus Gnus (), or Gnus Network User Services, is a message reader which is part of GNU Emacs. It supports reading and composing both e-mail and news and can also act as an RSS reader, web processor, and directory browser for both local and remote files ...

, which can take advantage of overview files for faster access to large mail folders. Many newer news servers store NOV data in a variety of formats. A specialized

database In computing, a database is an organized collection of data stored and accessed electronically. Small databases can be stored on a file system, while large databases are hosted on computer clusters or cloud storage. The design of databases sp ...

is frequently used in favor of the original flat file arrangement.

External links

Original NOV software distribution
(mirror at Funet, formerly hosted at ftp.std.com) *RFC 2980 describes the {{mono, XOVER command. Usenet