INTERNET DRAFT Davide Musella
draft-musella-html-meta-00.txt(???) National Research Council
November 1995
The META Tag of HTML
Status of this Memo
[...]
Abstract
This document define a strict synopsis for the META Tag of HTML.
The grammar will be extended to the contents of the HTTP-EQUIV field,
defining a set of words to use to allow cataloging of the document.
1.Introduction
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="Keywords" CONTENT="Italy, Tourism">
or
<META HTTP-EQUIV="Keys" CONTENT="Italy, Tourism">
could rappresent the same concepts with two differents 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 (HTML 2.0 definition)
The META element is used within the HEAD element to embed document
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:
NAME
CONTENT
HTTP-EQUIV
2.NAME.
This attributes could be used to define some property such as author,
publication date etc. If absent the name can be assumed to be the same as the
value of HTTP-EQUIV.
An example:
<META NAME="Editor" CONTENT="McDraw Bill">
Do not use the META element to define information that should be associated
with an existing HTML element.
This tag is not processed by the HTTP server.
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 not case
sensitive. If absent, the NAME attribute should be used to identify this
meta-information and it should not be used within an HTPP 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
expire: to indicate the expire date of the document
language: to indicate the language of the document
abstract: to indicate the abstract of the document
organization: to indicate the organization of the author
public (yes,no): to indicate if the document is available to averybody
or not
An HTTP server can process these tags for an HEAD HTTP request, but each
server can choose which one handle.
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. CONTENT
Used to supply a value for a named property.
If it's used with the HTTP-EQUIV 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 rappresent by the SPACE (ASCII[32]) and the OR
operator with the COMMA (ASCII[44]).
The AND operator is processed before the OR operator. So a string like this:
"Red ball, White ball" means :"ball AND (red OR white)".
Examples:
<META HTTP-EQUIV="Keywords" CONTENT="Italy Product,Italy Tourism">
The spaces between a comma and a word or viceversa are ignored.