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  
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   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".