Cross-reference
Encyclopedia
A cross-reference is an instance within a document
which refers to related or synonymous information elsewhere, usually within the same work. To cross-reference or to cross-refer (verb) is to make such connections. The term "cross-reference" is often abbreviated as x-ref, xref, or, in computer science, XR. Cross-referencing is usually employed to either verify claims made by an author or to link to another piece of work that is of related interest. See, for example, the Linux
cross-reference tool, LXR for init/main.c.
In an index
, a cross reference is often denoted by See Also. For example, under the term Albert Einstein in the index of a book about Nobel Laureates, there may be the cross-reference See Also: Einstein, Albert.
(XR) is maintained internally or externally to a document with either in-context (XRIC) or out-of-context (XROC) cross-referencing. These are analogous to KWIC and KWOC, which were very early computer applications inherited from the centuries-old idea of concordance
.
Traditionally, reference numbers and footnote marks are examples of in-context cross-referencing, whereas the index
and the reference list at the end of texts are examples of out-of-context cross-referencing. Out-of-context cross-referencing relies on the traditional, manually-produced indexes using subject or citation. This remained the mainstream text retrieval system until the advent of CD-ROM
in 1985, since which the digital text, the hypertext
, and eventually the World Wide Web
and search engines, provided systems for XRIC.
Soon after the advent of the Web, there was a rumor that XRIC features of the Web were better than the Gopher's XROC system. Charles Goldfarb
, one of the founding pioneers in SGML, satirically compared the antagonism between XROC and XRIC paradigms to a religious war, which would be moderately called the cross-reference war. While the Web surpassed Gopher, in that XRIC is better than XROC in hypertext, both are as complementary as the two sides of the coin. Unfortunately, however, the schism
between both text retrieval paradigms appears reflected on ACM/SIGIR and ACM/SIGWEB much overlapping each other.
The narrow or common sense of hypertext
implies XRIC, while the wide or true sense includes XROC as well. From the text retrieval point of view, hypertext as a new retrieval paradigm
, objecting to XROC or subjecting itself mainly to XRIC, sounds like a self-defeating misnomer, because text retrieval and cross-reference well comprise both XROC and XRIC in themselves. Ironically, hypertext was coined by Ted Nelson
who used to object to the wide spectrum of text retrieval or cross-reference and subject it mainly to the narrow idea of transclusion
, or simply quotation
, aiming for text patchwork rather than retrieval.
Document
The term document has multiple meanings in ordinary language and in scholarship. WordNet 3.1. lists four meanings :* document, written document, papers...
which refers to related or synonymous information elsewhere, usually within the same work. To cross-reference or to cross-refer (verb) is to make such connections. The term "cross-reference" is often abbreviated as x-ref, xref, or, in computer science, XR. Cross-referencing is usually employed to either verify claims made by an author or to link to another piece of work that is of related interest. See, for example, the Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
cross-reference tool, LXR for init/main.c.
In an index
Index (publishing)
An index is a list of words or phrases and associated pointers to where useful material relating to that heading can be found in a document...
, a cross reference is often denoted by See Also. For example, under the term Albert Einstein in the index of a book about Nobel Laureates, there may be the cross-reference See Also: Einstein, Albert.
Hypertext
Cross-referencing in hypertextHypertext
Hypertext is text displayed on a computer or other electronic device with references to other text that the reader can immediately access, usually by a mouse click or keypress sequence. Apart from running text, hypertext may contain tables, images and other presentational devices. Hypertext is the...
(XR) is maintained internally or externally to a document with either in-context (XRIC) or out-of-context (XROC) cross-referencing. These are analogous to KWIC and KWOC, which were very early computer applications inherited from the centuries-old idea of concordance
Concordance
Concordance can mean:* Concordance , a list of words used in a body of work, with their immediate contexts* Concordance , the presence of the same trait in both members of a pair of twins...
.
Traditionally, reference numbers and footnote marks are examples of in-context cross-referencing, whereas the index
Index (publishing)
An index is a list of words or phrases and associated pointers to where useful material relating to that heading can be found in a document...
and the reference list at the end of texts are examples of out-of-context cross-referencing. Out-of-context cross-referencing relies on the traditional, manually-produced indexes using subject or citation. This remained the mainstream text retrieval system until the advent of CD-ROM
CD-ROM
A CD-ROM is a pre-pressed compact disc that contains data accessible to, but not writable by, a computer for data storage and music playback. The 1985 “Yellow Book” standard developed by Sony and Philips adapted the format to hold any form of binary data....
in 1985, since which the digital text, the hypertext
Hypertext
Hypertext is text displayed on a computer or other electronic device with references to other text that the reader can immediately access, usually by a mouse click or keypress sequence. Apart from running text, hypertext may contain tables, images and other presentational devices. Hypertext is the...
, and eventually the World Wide Web
World Wide Web
The World Wide Web is a system of interlinked hypertext documents accessed via the Internet...
and search engines, provided systems for XRIC.
Soon after the advent of the Web, there was a rumor that XRIC features of the Web were better than the Gopher's XROC system. Charles Goldfarb
Charles Goldfarb
Charles F. Goldfarb is known as the father of SGML and is a co-inventor of the concept of markup languages. In 1969 Charles Goldfarb, leading a small team at IBM, developed the first markup language, called Generalized Markup Language, or GML. In an , Dr...
, one of the founding pioneers in SGML, satirically compared the antagonism between XROC and XRIC paradigms to a religious war, which would be moderately called the cross-reference war. While the Web surpassed Gopher, in that XRIC is better than XROC in hypertext, both are as complementary as the two sides of the coin. Unfortunately, however, the schism
Schism (religion)
A schism , from Greek σχίσμα, skhísma , is a division between people, usually belonging to an organization or movement religious denomination. The word is most frequently applied to a break of communion between two sections of Christianity that were previously a single body, or to a division within...
between both text retrieval paradigms appears reflected on ACM/SIGIR and ACM/SIGWEB much overlapping each other.
The narrow or common sense of hypertext
Hypertext
Hypertext is text displayed on a computer or other electronic device with references to other text that the reader can immediately access, usually by a mouse click or keypress sequence. Apart from running text, hypertext may contain tables, images and other presentational devices. Hypertext is the...
implies XRIC, while the wide or true sense includes XROC as well. From the text retrieval point of view, hypertext as a new retrieval paradigm
Paradigm
The word paradigm has been used in science to describe distinct concepts. It comes from Greek "παράδειγμα" , "pattern, example, sample" from the verb "παραδείκνυμι" , "exhibit, represent, expose" and that from "παρά" , "beside, beyond" + "δείκνυμι" , "to show, to point out".The original Greek...
, objecting to XROC or subjecting itself mainly to XRIC, sounds like a self-defeating misnomer, because text retrieval and cross-reference well comprise both XROC and XRIC in themselves. Ironically, hypertext was coined by Ted Nelson
Ted Nelson
Theodor Holm Nelson is an American sociologist, philosopher, and pioneer of information technology. He coined the terms "hypertext" and "hypermedia" in 1963 and published it in 1965...
who used to object to the wide spectrum of text retrieval or cross-reference and subject it mainly to the narrow idea of transclusion
Transclusion
In computer science, transclusion is the inclusion of a document or part of a document into another document by reference.For example, an article about a country might include a chart or a paragraph describing that country's agricultural exports from a different article about agriculture...
, or simply quotation
Quotation
A quotation or quote is the repetition of one expression as part of another one, particularly when the quoted expression is well-known or explicitly attributed by citation to its original source, and it is indicated by quotation marks.A quotation can also refer to the repeated use of units of any...
, aiming for text patchwork rather than retrieval.