Specification For HTML Meta Element with Name Value Subject-System
Section 1: Introduction
This is the specification for the HTML meta element with the name attribute value set to “subject-system”. This is version 1.0.2 of this specification.
HTML is the HyperText Markup Language, which is a commonly used, perhaps the most commonly used, non-natural language for pages hosted on the World Wide Web. HTML is generally written approximately in accordance with specifications that have been revised several times. Two of those HTML specifications are the HTML Living Standard (as updated and (One-Page Version treated here as if authoritative) (<https://html.spec.whatwg.org/>, as accessed and )) and HTML 5.1 (version of ) (<http://www.w3.org/TR/html51/single-page.html>, as accessed before and on ). The HTML Living Standard is maintained by the Web Hypertext Application Technology Working Group (WHATWG) and HTML 5.1 is maintained by the World Wide Web Consortium (W3C). Each of those HTML specifications specifies numerous elements and, in section 4.2.5 of each such HTML specification, one such element is the meta element. For that element, each of those HTML specifications specifies attributes including the name attribute, specifies some names that can be values for that attribute (limited to one such value per such attribute per such element), and provides, in section 184.108.40.206 of each such HTML specification, a means by which extensional or additional names may be proposed to be values for that attribute, each such proposal to include a link to a specification for that extensional or additional name. This specification may appropriately be linked to from such a proposal.
This specification, as published on this page and which, except as otherwise stated, is normative, shall also apply, insofar as compatible, to any specification of the HTML Living Standard or of HTML 5.1 other than those referenced above and of any version preceding or succeeding HTML 5.1; except that it shall not apply to any page authored before this specification was first published (the date of such first publication being stated below).
Sec. 1.1: Definitions and Construction
The words and phrases must, must not, required, shall, shall not, should, should not, recommended, may, and optional in this specification and regardless of capitalization are to be interpreted as described in RFC 2119 (also known as BCP 14).
A subject system is a ‘taxonomy or classification system of all subjects of knowledge, in which, generally, each subject is represented by at least a name, a number, or another symbol’.
In this specification, if a string, including a null string and a non-null string with no visible or displaying characters, is rendered (including being displayed) with or surrounded by single quotation marks which are curved when a font in which this specification may be displayed has single quotation marks as both straight and curved or is rendered (including being displayed) with or surrounded by double quotation marks which are curved when a font in which this specification may be displayed has double quotation marks as both straight and curved, then the quotation marks that may thus be curved are, unless otherwise stated in this specification, not part of the string. Thus, generally, the string represented by “example” is only seven characters long, not nine.
Sec. 1.2: Problem Being Solved
This subsection is non-normative.
A page may be classified by its subject, much as books in a public or academic library are typically classified using one of several standard subject classification systems, such as, in the United States, the Library of Congress Subject Headings or the Dewey Decimal Classification. There is already at least one meta element for identifying the subject, the meta element named “dcterms.subject”, but it does not identify which classification system supports the subject chosen. Therefore, a way to identify that classification system itself is needed.
Because a classification system may be revised from time to time and thereby may gain or lose particular subject classifications, because an old classification system may have been used for a Web page, and because not every page author will or can keep updating the meta element for the latest subject system edition, that identification should indicate the classification system edition that was used, even if old.
Compliance with copyright law in whether to use a certain classification system should be left to the page author or the website owner.
Sec. 2: Warning on Copyright
A subject system may be under copyright and may not be available for use without the permission of the copyright owner of the system, even though another subject system is so available and even though a subject system in question is widely used elsewhere. This specification is not definitive on rights under copyright law. Law may vary from nation to nation. The page author is responsible for compliance with all law. The owner of the website of which the page is part is responsible for compliance with all law.
Sec. 3: Method
There may be an HTML meta element with the name attribute value set to “subject-system” (herein known as such meta “subject-system” element) and, if such meta “subject-system” element is present, it shall have the content attribute value set to a string identifying one and only one subject system. Such string shall be as specified below. There shall not be more than one such meta “subject-system” element. If there is more than one such meta “subject-system” element, only the first such meta “subject-system” element shall be determinative and all other such meta “subject-system” elements shall be ignored. In the only such meta “subject-system” element or in the determinative such meta “subject-system” element, if the content attribute value purports to identify more than one subject system, only the first such subject system shall be determinative and all other subject systems shall be ignored.
Sec. 3.1: Content Attribute Values
All values are public or private.
Sec. 3.1.1: Lists of Public Values
If a language is to be indicated as part of a value, the language shall be represented by the two-letter language codes provided by ISO 639-1.
Bibliographic details except for the title are non-normative. If the title of the publication is changed in the publication so as not to be what this specification cites, the changed title is normative.
Sec. 220.127.116.11: Library of Congress Subject Headings (Washington, D.C., U.S.: Library of Congress): List
- lcsh (if edition unknown or continuously updated)
- lcsh-1 (1st edition)
- lcsh-2 (2d edition)
- lcsh-3 (3d edition)
- lcsh-. . . (number for any in-between edition) (periods and spaces are not part of the value)
- lcsh-21 (28th edition)
- lcsh-22 (29th edition)
- lcsh-23 (30th edition)
- lcsh-. . . (number for any subsequent edition) (periods and spaces are not part of the value)
Sec. 18.104.22.168: Dewey Decimal Classification (Dublin, Oh., U.S.: OCLC Online Computer Library Center, Inc.)
Sec. 22.214.171.124.1: Note on Dewey Decimal Classification
Non-normatively, it is noted that copyright may constrain use of the Dewey Decimal Classification for websites and Web pages even though widely used for books in public libraries.
Sec. 126.96.36.199.2: List for Dewey Decimal Classification
- ddc (if edition unknown or continuously updated)
- ddc-1 (1st edition)
- ddc-2 (2d edition)
- ddc-3 (3d edition)
- ddc-. . . (number for any intervening edition) (periods and spaces are not part of the value)
- ddc-21 (21st edition)
- ddc-22 (22d edition)
- ddc-23 (23d edition)
- ddc-. . . (number for any subsequent edition) (periods and spaces are not part of the value)
Sec. 188.8.131.52: Universal Decimal Classification (The Hague, Netherlands: UDC Consortium): List
- udc (if language unknown and if edition unknown or continuously updated)
- udc-fr-1 (in French, 1st edition)
- udc-. . -. . . (language and either number or year for any intervening edition) (periods and spaces are not part of the value)
- udc-en-2003 (English 2003 edition)
- udc-. . -. . . (language and either number or year for any subsequent edition) (periods and spaces are not part of the value)
Sec. 184.108.40.206: Chinese Library Classification (Beijing, People’s Republic of China: National Library of China Publishing House): List
- clc (if edition unknown or continuously updated)
- clc-. . . (edition number or year for any edition) (periods and spaces are not part of the value)
Sec. 3.1.2: Proposing Additional Content Attribute Values For Public Values
Anyone may propose adding one or more values to the above lists. Information that generally would be helpful to a decision so to add includes:
Not all of the information must be provided, but it probably would be helpful for a faster decision.
A value string may also be proposed. The proposed value should be composed of a substring representing the title of the subject system itself regardless of edition and preferably easily recognizable, if the system is published separately in more than one language a hyphen and a substring briefly representing the language (standard two-letter codes are preferred unless a three-letter code is required for a language), and, unless an edition is unknown, a hyphen and a substring briefly representing the edition (often just a number or, if unnumbered, a year).
A proposal may be sent to a current author or editor of this specification via appropriate contact information that may be linked to on this page.
Sec. 3.1.3: Private Values
If such meta “subject-system” element is on a page that is not to be exposed to the Internet, in the content attribute value a publicly-undefined token may be present provided that “private” as a caseless space-separated token is also present. A creator may create or accept a private definition for the publicly-undefined token and an owner of an off-Internet intranet or single computer may, insofar as allowed by law other than this specification, require such acceptance of such a private definition. In the event that such meta “subject-system” element with such a content attribute value (including the token “private”) is exposed to the Internet, a user agent shall process the element as if the publicly-undefined token is absent, even if the publicly-undefined token would otherwise be valid under this specification.
Sec. 4: Security, Synonymy, History, and Backwards Compatibility
This section is non-normative except as otherwise stated.
Sec. 4.1: Security
No security implication has been identified with respect to this specification.
Sec. 4.2: Synonymy
Normatively, an HTML meta element with the name attribute value set to “subject-system” is an approximately synonymous replacement for an HTML meta element with the name attribute value set to “subj-. . .”. Non-normatively, it is noted that the value “subj-. . .” may not have been widely implemented, if at all, due to an effort to reserve a namespace, which effort may have failed.
Sec. 4.3: History
The original author and editor of this specification, except as otherwise stated, was Nick Levinson, who can be contacted through a link on this page.
Version 1 was published on this page on . Version 1 was revised into version 1.0.1, published on . Version 1.0.1 was revised into this version.
The history of the name attribute value “subj-. . .” is entirely at the official page of HTML meta element extensions (scroll to “subj-. . .”); its history at WHATWG begins at , at https://wiki.whatwg.org/index.php?title=MetaExtensions&oldid=37274 (with the page differences at https://wiki.whatwg.org/index.php?title=MetaExtensions&diff=3727&oldid=3705) and continues at , at https://wiki.whatwg.org/index.php?title=MetaExtensions&oldid=3810 (with the page differences at https://wiki.whatwg.org/index.php?title=MetaExtensions&diff=3810&oldid=3732), whether revised or not (it probably was not) in the course of being moved on the WHATWG MetaExtensions wiki page then at , at https://wiki.whatwg.org/index.php?title=MetaExtensions&oldid=5908 (with the page differences at https://wiki.whatwg.org/index.php?title=MetaExtensions&diff=5908&oldid=5604), at , at https://wiki.whatwg.org/index.php?title=MetaExtensions&oldid=6432 (with the page differences at https://wiki.whatwg.org/index.php?title=MetaExtensions&diff=6432&oldid=6431), and at , at https://wiki.whatwg.org/index.php?title=MetaExtensions&oldid=6557 (with the page differences at https://wiki.whatwg.org/index.php?title=MetaExtensions&diff=6557&oldid=6519).
Sec. 4.4: Backwards Compatibility
Backwards compatibility is intended.
Sec. 5: Intellectual Property with This Specification
Sec. 5.1: Copyright Status
Insofar as lawful, with respect to the CC0 1.0 Universal legal tool (herein “CC0”) (summarized at https://creativecommons.org/publicdomain/zero/1.0/) (both URLs as accessed ) of the Creative Commons Corporation, Nick Levinson, the original author and editor of this specification, has, upon first publication of this specification, hereby become the Affirmer under CC0 and hereby elected to apply CC0 to this specification, to publicly distribute this specification, and to make this specification available all as provided for in CC0 and hereby waived, abandoned, surrendered, granted, affirmed, offered, and disclaimed all as provided for in CC0 with respect to this specification.
Sec. 5.2: Trademarks, Endorsements, and Associations
“Creative Commons” is a trademark of Creative Commons Corporation; use of such trademark does not imply endorsement by or association with Creative Commons Corporation.
“CC0” is a trademark of Creative Commons Corporation; use of such trademark does not imply endorsement by or association with Creative Commons Corporation.
“Dewey Decimal Classification”, “Dewey”, “DDC”, and “OCLC” are each a registered trademark of OCLC Online Library Center, Inc., and copyright or lack thereof for this specification does not affect the rights of OCLC Online Library Center, Inc., with respect to any such trademark.
Sec. 5.3: Other Claims
Except as otherwise referenced, the original author and editor of this specification, Nick Levinson, is not aware of any claim by any other person or entity to intellectual property adversely affecting this specification.
Sec. 6: Section Titles Not Restrictive
Titles of sections, including subsections at all subsectional depths, are provided solely for convenience and do not restrict the meaning of the content of the respective sections. Titles of sections include headlines of sections.