As per Relevance of the word parameter, we have this rfc below:
Network Working Group L.
Request for Comments: 2397 Xerox
Category: Standards Track August 1998
The "data" URL
Status of this
This document specifies an Internet standards track protocol for
Internet community, and requests discussion and suggestions
improvements. Please refer to the current edition of the "
Official Protocol Standards" (STD 1) for the standardization
and status of this protocol. Distribution of this memo is unlimited
Copyright
Copyright (C) The Internet Society (1998). All Rights Reserved
1.
A new URL scheme, "data", is defined. It allows inclusion of
data items as "immediate" data, as if it had been
externally
2.
Some applications that use URLs also have a need to embed (small
media type data directly inline. This document defines a new
scheme that would work like 'immediate addressing'. The URLs are
the form
data:[][;base64],
The is an Internet media type specification (
optional parameters.) The appearance of ";base64" means that the
is encoded as base64. Without ";base64", the data (as a sequence
octets) is represented using ASCII encoding for octets inside
range of safe URL characters and using the standard %xx hex
of URLs for octets outside that range. If is omitted,
defaults to text/plain;charset=US-ASCII. As a shorthand
"text/plain" can be omitted but the charset parameter supplied
The "data:" URL scheme is only useful for short values. Note
some applications that use URLs may impose a length limit;
example, URLs embedded within anchors in HTML have a length
determined by the SGML declaration for HTML [RFC1866]. The
(1024) limits the number of characters which can appear in a
Masinter Standards Track [Page 1]
RFC 2397 The "data" URL scheme August 1998
attribute value literal, the ATTSPLEN (2100) limits the sum of
lengths of all attribute value specifications which appear in a tag
and the TAGLEN (2100) limits the overall length of a tag
The "data" URL scheme has no relative URL forms
3.
dataurl := "data:" [ mediatype ] [ ";base64" ] ","
mediatype := [ type "/" subtype ] *( ";" parameter )
data := *
parameter := attribute "="
where "urlchar" is imported from [RFC2396], and "type", "subtype",
"attribute" and "value" are the corresponding tokens from [RFC2045],
represented using URL escaped encoding of [RFC2396] as necessary
Attribute values in [RFC2045] are allowed to be either represented
tokens or as quoted strings. However, within a "data" URL,
"quoted-string" representation would be awkward, since the quote
is itself not a valid urlchar. For this reason, parameter
should use the URL Escaped encoding instead of quoted string if
parameter values contain any "tspecial".
The ";base64" extension is distinguishable from a content-
parameter by the fact that it doesn't have a following "=" sign
4.
A data URL might be used for arbitrary types of data. The
data:,A%20brief%20
encodes the text/plain string "A brief note", which might be
in a footnote link
The HTML fragment
<
SRC="data:image/gif;base64,R0lGODdhMAAwAPAAAAAAAP///
AAAC8IyPqcvt3wCcDkiLc7C0qwyGHhSWpjQu5
ByTB10QgxOR0TqBQejhRNzOfkVJ+5YiUqrXF5Y5lKh/DeuNcP5
a/TPg7JpJHxyendzWTBfX0cxOnKPjgBzi4diinWGdkF8
ZeGl9i2icVqaNVailT6F5iJ90m6mvuTS4OK05M0vDk0Q4XUtwvKOzrcd3iq9
F81M1OIcR7lEewwcLp7tuNNkM3uNna3F2JQFo97Vriy/Xl4/f1cf5VWzXyym7
hhx4dbgYKAAA7"
ALT="Larry">
Masinter Standards Track [Page 2]
RFC 2397 The "data" URL scheme August 1998
could be used for a small inline image in a HTML document. (
embedded image is probably near the limit of utility. For
else larger, data URLs are likely to be inappropriate.)
A data URL scheme's media type specification can include
parameters; for example, one might specify a charset parameter
data:text/plain;charset=iso-8859-7,%be%fg%
can be used for a short sequence of greek characters
Some applications may use the "data" URL scheme in order to
setup parameters for other kinds of networking applications.
example, one might create a media
application/vnd-xxx-
whose content consists of a query string and a database
for the "xxx" vendor's databases. A URL of the form
data:application/vnd-xxx
query,select_vcount,fcol_from_fieldtable/
could then be used in a local application to launch the "helper"
application/vnd-xxx-query and give it the immediate data included
5.
This idea was originally proposed August 1995. Some versions of
data URL scheme have been used in the definition of VRML, and
version has appeared as part of a proposal for embedded data in HTML
Various changes have been made, based on requests, to elide the
type, pack the indication of the base64 encoding more tightly,
eliminate "quoted printable" as an encoding since it would not
yield valid URLs without additional %xx encoding, which itself
sufficient. The "data" URL scheme is in use in VRML, new
of HTML, and various commercial products. It is being used for
parameters in Java and ActiveX applications
6.
Interpretation of the data within a "data" URL has the same
considerations as any implementation of the given media type.
application should not interpret the contents of a data URL which
marked with a media type that has been disallowed for processing
the application's configuration
Masinter Standards Track [Page 3]
RFC 2397 The "data" URL scheme August 1998
Sites which use firewall proxies to disallow the retrieval of
media types (such as application script languages or types with
security problems) will find it difficult to screen against
inclusion of such types using the "data" URL scheme. However,
should be aware of the threat and take whatever precautions
considered necessary within their domain
The effect of using long "data" URLs in applications is
unknown; some software packages may exhibit unreasonable
when confronted with data that exceeds its allocated buffer size
7.
[RFC2396] Berners-Lee, T., Fielding, R., and L. Masinter
"Uniform Resource Identifiers (URI): Generic Syntax",
2396, August 1998.
[RFC1866] Berners-Lee, T., and D. Connolly, "Hypertext
Language - 2.0.", RFC 1866, November 1995.
[RFC2045] Freed N., and N. Borenstein., "Multipurpose Internet
Extensions (MIME) Part One: Format of Internet
Bodies", RFC 2045, November 1996.
Author contact information
Larry
Xerox Palo Alto Research
3333 Coyote Hill
Palo Alto, CA 94304
EMail: masinter@parc.xerox.
Masinter Standards Track [Page 4]
RFC 2397 The "data" URL scheme August 1998
Full Copyright
Copyright (C) The Internet Society (1998). All Rights Reserved
This document and translations of it may be copied and furnished
others, and derivative works that comment on or otherwise explain
or assist in its implementation may be prepared, copied,
and distributed, in whole or in part, without restriction of
kind, provided that the above copyright notice and this paragraph
included on all such copies and derivative works. However,
document itself may not be modified in any way, such as by
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TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED,
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE
Masinter Standards Track [Page 5]
if you see any problems within the linking, don't worry be happy,
this is version 0.1 of the Relevance System and you gotta expect some crappy subroutines sometimes,
just be content we did not write this in Java, which would have made this "bigger and better" HAHAHHA.
RFC documents can be found at I.E.T.F.
Relevance System Copyright © 2002 Spectrum WorldResearch
other technical nosh by ServerMasters Corporation
collaboration of BobX
