INTERNET DRAFT Davide Musella draft-musella-html-metatag-02.txt National Research Council January 29, 1996 Expires in six months The META Tag of HTML Status of this Memo This document is an Internet-Draft. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet- Drafts as reference material or to cite them other than as ``work in progress.'' To learn the current status of any Internet-Draft, please check the "1id-abstracts.txt" listing contained in the Internet-Drafts shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East Cost) or ftp.isi.edu (US West Coast). Distribution of this document is unlimited. Please send comments to Davide Musella, davidmsl@anti.tesi.dsi.unimi.it or to davide@jargo.itim.mi.cnr.it , (voice) +39.(0)2.70643271 Abstract This document defines a strict synopsis for the META Tag of HTML. The grammar is extended to the contents of the HTTP-EQUIV field, defining a set of words to use to allow document cataloguing. 1. Introduction Now the synopsis of the META HTTP-EQUIV Tag is not severe, allowing so the use of different key words to define the same things. The functions like this: <META HTTP-EQUIV = "author" CONTENT = "Pennac, Rossi"> or: <META HTTP-EQUIV = "writer" CONTENT = "Pennac, Rossi"> could reppresent the same concepts with two different syntax. The aim of this Draft is to define which are the words to use to define the contents of an HTML document. There are, also, some easy rules to implement a binary logic (AND or OR) for the CONTENT field. 2. The META Tag The META element is used within the HEAD element to embed documents meta-information not defined by other HTML elements. Such information can be extracted by servers/clients for use in identifying, indexing and cataloging specialized document meta-information. Although it is generally preferable to used named elements that have well defined semantics for each type of meta-information, such as title, this element is provided for situations where strict SGML parsing is necessary and the local DTD is not extensible. In addition, HTTP servers can read the contents of the document head to generate response headers corresponding to any elements defining a value for the attribute HTTP-EQUIV. This provides document authors with a mechanism (not necessarily the preferred one) for identifying information that should be included in the response headers of an HTTP request. The META element has three attributes: - HTTP-EQUIV - NAME - CONTENT The HTTP-EQUIV and the NAME attributes are mutually exclusives. 3. HTTP-EQUIV. This attribute binds the element to an HTTP response header. If the semantics of the HTTP response header named by this attribute is known, then the contents can be processed based on a well defined syntactic mapping, whether or not the DTD includes anything about it. HTTP header names are case insensitive. If absent, the NAME attribute should be used to identify the meta-information and it should not be used within an HTTP response header. It is possible to use any text string, but if you want to define these properties you have to use the following words: keywords: to indicate the keywords of the document author: to indicate the author of the document timestamp: to indicate when the document is authored (HTTP-date format) expire: to indicate the expire date of the document (HTTP-date format) language: to indicate the language of the document (using ISO3316 code or ISO639 code) abstract: to indicate the abstract of the document organization: to indicate the organization of the author revision: to indicate the revision number of the document (format: 00, 01, 02, or 000, 001, ...) An HTTP server must process these tags for an HEAD HTTP requestr. Do not name an HTTP-EQUIV attribute the same as a response header that should typically only be generated by the HTTP server. Some inappropriate names are "Server", "Date", and "Last-Modified". Whether a name is inappropriate depends on the particular server implementation. It is recommended that servers ignore any META elements that specify HTTP equivalents (case insensitively) to their own reserved response headers. 4. NAME. This attributes can be used to define some properties such as "number of pages" or "preferred browser" or any info an author want to insert in his document. The keywords indicates in the previous paragraph for the HTTP-EQUIV are still valid also in the NAME context. An example: <META NAME= "Maybe Published By" CONTENT = "McDraw Bill"> or <META NAME= "keywords" CONTENT = "manual, scouting"> Do not use the META element to define information that should be associated with an existing HTML element. 5. CONTENT Used to supply a value for a named property. It can contain more than one single information; it is possible to use the Boolean operator (AND, OR) to insert a Boolean definition of the field. The AND operator will be represented by the SPACE (ASCII[32]) and the OR operator by the COMMA (ASCII[44]). The AND operator is processed before the OR operator. So a string like this: "Red ball, White pen" means :"(Red AND ball) OR (White AND pen)". Example: <META HTTP-EQUIV= "Keywords" CONTENT= "Italy Products, Italy Tourism"> The spaces between a comma and a word or vice versa are ignored. 6. Cataloguing an HTML document These 'keywords' were specifically conceived to catalogue HTML documents. This allows the software agents to index at best your own document. To do a preliminary indexing, it's important to use at least the HTTP-EQUIV meta-tag "keywords".