RSS 0.91 Spec, revision 3
Netscape Communications
Primary Author: Dan Libby
July 10, 1999
Notes
Files must be 100% valid XML. We're trying to move towards a more standard
format, and to this end we have included several tags from the popular
<scriptingNews> format. We have also ensured that this version is 100%
valid XML. We did this by requiring that a DOCTYPE tag be included, and
validating each RSS document against that DTD. This means that it is not enough
for an RSS document to be "well-formed". It must also be "valid" with respect to
its DTD.
No mixed content tags. We are specifically not including any tags that
contain mixed content in RSS 0.91. This means that each tag either contains
sub-tags only, or text only, not a combination. This is both because we want to
keep the format simple, and because our current validation system is not able to
handle this type of tag. We also are not allowing any HTML markup beyond the
commonly used entities such as " A full list of these are defined in
the RSS 0.91 DTD.
New tags for syndication community. Our validator will now allow several new
tags through the system, though most of them will not actually be used by
Netcenter. However, these may work when syndicating content to other sites.
These tags are noted explicitly in the spec as "ignored."
RDF references removed. RSS was originally conceived as a metadata format
providing a summary of a website. Two things have become clear: the first is
that providers want more of a syndication format than a metadata format. The
structure of an RDF file is very precise and must conform to the RDF data model
in order to be valid. This is not easily human-understandable and can make it
difficult to create useful RDF files. The second is that few tools are available
for RDF generation, validation and processing. For these reasons, we have
decided to go with a standard XML approach.
Specification
Tags in alphabetical order.
<channel>
Description
information about a particular channel. Everything pertaining to an
individual channel is contained within this tag.
Netcenter Usage
Currently displayed on "My Netscape". May use in other locations in the
future.
Attributes
none
Sub-elements:
Examples
See example
1
<copyright>
Description
copyright string
Netcenter Usage
ignored
Attributes
none
Sub-elements:
none
Examples
See example
2
<day>
Description
The day of the week, spelled out in English.
Netcenter Usage
ignored
Attributes
none
Sub-elements:
none
Examples
See example
2
<description>
Description
a plain text description of an item, channel, image, or textinput.
Netcenter Usage
displayed as appropriate depending on context.
Attributes
none
Sub-elements:
none
Examples
See example
channels
<docs>
Description
This tag should contain a URL that references a description of the
channel.
Netcenter Usage
ignored
Attributes
none
Sub-elements:
none
Examples
See example
2
<!DOCTYPE>
Description
Document Type Identifier. This is an XML tag that identifies where to find
the definition for this format. It should follow the xml
tag. The full DTD is here.
Netcenter Usage
required to ensure document validity
Attributes
- 1 of these two formats is required:
- rss PUBLIC "-//Netscape Communications//DTD RSS 0.91//EN" ""
- rss PUBLIC "-//Netscape Communications//DTD RSS 0.91//EN"
"http://my.netscape.com/publish/formats/rss-0.91.dtd"
Sub-elements:
none
Examples
<![CDATA[<!DOCTYPE rss PUBLIC "-//Netscape Communications//DTD RSS 0.91//EN" "http://my.netscape.com/publish/formats/rss-0.91.dtd">
]]><![CDATA[<!DOCTYPE rss PUBLIC "-//Netscape Communications//DTD RSS 0.91//EN" "">
]]>
<height>
Description
Specifies the height of an image.
Should be an integer value.
Netcenter Usage
The value must be between 1 and 400. If ommitted, the default value is
31.
Attributes
none
Sub-elements:
none
Examples
See image
<hour>
Description
Specifies an hour of the day. Should be an integer value between 0 and 23.
See skipHours.
Netcenter Usage
ignored
Attributes
none
Sub-elements:
none
Examples
See skipHours
<image>
Description
Specifies an image associated with a channel.
Netcenter Usage
Optionally (user preference) display an image along with the channel
content.
Attributes
none
Sub-elements:
Examples
<![CDATA[<image>
<url>http://my.site.com/images/1.gif</url>
<link>http://my.site.com/index.html</link>
<title>my image alt text</title>
</image>
]]><![CDATA[<image>
<url>http://my.site.com/images/1.gif</url>
<link>http://my.site.com/index.html</link>
<title>my image alt text</title>
<width>120</width>
<height>200</height>
</image>
]]>
<item>
Description
An item that is associated with a channel.
The item should represent a web-page, or subsection within a web page. It should
have a unique URL associated with it. Each item must contain a title and a link.
A description is optional.
Netcenter Usage
generates a list of links. The description, if supplied, may optionally be
viewed by the user as plain text beneath the link. Also, a maximum of 15 items
per channel is enforced at this time.
Attributes
none
Sub-elements:
Examples
<![CDATA[<item>
<title>Item #1</title>
<link>http://my.site.com/story1/index.html</link>
</item>
]]><![CDATA[<item>
<title>Item #2</title>
<link>http://my.site.com/story2/index.html</link>
<description>Some stuff about this item</description>
</item>
]]>
<language>
Description
Specifies the language of a channel.
See supported
language codes
Netcenter Usage
used to assist user with determining correct page encoding
Attributes
none
Sub-elements:
none
Examples
See example
1
<lastBuildDate>
Description
The last time the channel was modified.
Netcenter Usage
ignored
Attributes
none
Sub-elements:
none
Examples
See example
2
<link>
Description
This is a url that a user is expected to click on, as opposed to a <url>
that is for loading a resource, such as an image.
Netcenter Usage
must start with either "http://" or "ftp://". All other urls are considered
invalid.
Attributes
none
Sub-elements:
none
Examples
See examples
<managingEditor>
Description
The email address of the managing editor of the site, the person to contact
for editorial inquiries
Netcenter Usage
ignored
Attributes
none
Sub-elements:
none
Examples
See example
2
<name>
Description
The name of an object, corresponding to the "name" attribute of an HTML
<INPUT> element. Currently, this only applies to textinput.
Netcenter Usage
generates "name" attribute in html form
Attributes
none
Sub-elements:
none
Examples
See textinput
<pubDate>
Description
Date when channel was published.
Netcenter Usage
ignored
Attributes
none
Sub-elements:
none
Examples
See example
2
<rating>
Description
- recommended links rating agencies:
- http://www.w3.org/PICS/raters.htm (W3 maintained list of rating agency
links)
- RSACi http://www.rsac.org (Click on 'register' link)
- SafeSurf http://www.safesurf.com/
http://www.safesurf.com/classify/index.html (direct)
- User actions:
- Obtain a rating for your site from a well-known rating agency (eg RSACi,
SafeSurf)
- Copy rating data into RSS file. Include only the data within the
'content=' attribute.
- Expected format:
Netcenter Usage
ignored. May use in the future to dynamically decide page rating.
Attributes
none
Sub-elements:
none
Examples
<![CDATA[Tag obtained from rating agency: <META http-equiv="PICS-Label" content='(PICS-1.1 "http://www.classify.org/safesurf/" l r (SS~~000 1))'>
RSS Rating tag: <rating>(PICS-1.1 "http://www.classify.org/safesurf/" l r (SS~~000 1))</rating>
]]>
<rss>
Description
Identifies begin and end of rss content.
Netcenter Usage
identifies content type
Attributes
Sub-elements:
Examples
<![CDATA[<rss version="0.91">
<channel>
...
</channel>
</rss>
]]>
<skipDays>
Description
A list of <day>s of the week, in English, indicating the days of the
week when your channel will not be updated. As with activeHours, if you know
your channel will never be updated on Saturday or Sunday, for example
Netcenter Usage
ignored
Attributes
none
Sub-elements:
Examples
<![CDATA[<skipDays>
<day>Saturday</day>
<day>Sunday</day>
</skipDays>
]]>
<skipHours>
Description
A list of <hour>s indicating the hours in the day, GMT, when the
channel is unlikely to be updated. If this sub-item is omitted, the channel is
assumed to be updated hourly.
Netcenter Usage
ignored
Attributes
none
Sub-elements:
Examples
<![CDATA[<skipHours>
<hour>6</hour>
<hour>7</hour>
<hour>8</hour>
<hour>9</hour>
<hour>10</hour>
<hour>11</hour>
</skipHours>
]]>
<textinput>
Description
An input field for the purpose of allowing users to submit queries back to
the publisher's site. This element should have a title, a link (to a cgi or
other processor), a description containing some instructions, and a name, to be
used as the name in the HTML tag <input type=text
name="[name]">
Netcenter Usage
Displays form for submission back to publisher.
Attributes
none
Sub-elements:
Examples
<![CDATA[<textinput>
<title>Search Now!</title>
<description>Enter your search <terms></description>
<name>find</name>
<link>http://my.site.com/search.cgi</link>
</textinput>
]]>
<title>
Description
An identifying string for a resource. When used in an item, this is the name
of the item's link. When used in an image, this is the Alt text for the image.
When used in a channel, this is the channel's title. When used in a textinput,
this is the the textinput's title.
Netcenter Usage
displayed as appropriate depending on context.
Attributes
none
Sub-elements:
none
Examples
See examples
<url>
Description
Location to load a resource from. Note that this is slightly different from
the link
tag, which specifies where a user should be re-directed to if a resource is
selected.
Netcenter Usage
must start with either "http://" or "ftp://". All other urls are considered
invalid.
Attributes
none
Sub-elements:
none
Examples
See image
<webMaster>
Description
The email address of the webmaster for the site, the person to contact if
there are technical problems with the channel.
Netcenter Usage
ignored
Attributes
none
Sub-elements:
none
Examples
See example
2
<width>
Description
Specifies the width of an image.
Should be an integer value.
Netcenter Usage
The value must be between 1 and 144. If ommitted, the default value is
88.
Attributes
none
Sub-elements:
none
Examples
See image
<?xml?>
Description
Identifies this as an XML document and specifies encoding. see w3c Note that this must be on
the first line of the document.
Netcenter Usage
required for XML compliance.
Attributes
- version: must be "1.0"
- encoding: see list
Sub-elements:
none
Example usage:
<![CDATA[<?xml version="1.0"?>]]><![CDATA[<?xml version="1.0" encoding="utf-8"?>]]><![CDATA[<?xml version="1.0" encoding="Shift_JIS"?>]]>
Example 1 - Simple
<![CDATA[<?xml version="1.0"?>
<!DOCTYPE rss SYSTEM "http://my.netscape.com/publish/formats/rss-0.91.dtd">
<rss version="0.91">
<channel>
<language>en</language>
<description>News and commentary from the cross-platform scripting community.</description>
<link>http://www.scripting.com/</link>
<title>Scripting News</title>
<image>
<link>http://www.scripting.com/</link>
<title>Scripting News</title>
<url>http://www.scripting.com/gifs/tinyScriptingNews.gif</url>
</image>
</channel>
</rss>
]]>
Example 2 - Complete
<![CDATA[<?xml version="1.0"?>
<!DOCTYPE rss SYSTEM "http://my.netscape.com/publish/formats/rss-0.91.dtd">
<rss version="0.91">
<channel>
<copyright>Copyright 1997-1999 UserLand Software, Inc.</copyright>
<pubDate>Thu, 08 Jul 1999 07:00:00 GMT</pubDate>
<lastBuildDate>Thu, 08 Jul 1999 16:20:26 GMT</lastBuildDate>
<docs>http://my.userland.com/stories/storyReader$11</docs>
<description>News and commentary from the cross-platform scripting community.</description>
<link>http://www.scripting.com/</link>
<title>Scripting News</title>
<image>
<link>http://www.scripting.com/</link>
<title>Scripting News</title>
<url>http://www.scripting.com/gifs/tinyScriptingNews.gif</url>
<height>40</height>
<width>78</width>
<description>What is this used for?</description>
</image>
<managingEditor>dave@userland.com (Dave Winer)</managingEditor>
<webMaster>dave@userland.com (Dave Winer)</webMaster>
<language>en-us</language>
<skipHours>
<hour>6</hour>
<hour>7</hour>
<hour>8</hour>
<hour>9</hour>
<hour>10</hour>
<hour>11</hour>
</skipHours>
<skipDays>
<day>Sunday</day>
</skipDays>
<rating>(PICS-1.1 "http://www.rsac.org/ratingsv01.html" l gen true comment "RSACi North America Server" for "http://www.rsac.org" on "1996.04.16T08:15-0500" r (n 0 s 0 v 0 l 0))</rating>
<item>
<title>stuff</title>
<link>http://bar</link>
<description>This is an article about some stuff</description>
</item>
<textinput>
<title>Search Now!</title>
<description>Enter your search <terms></description>
<name>find</name>
<link>http://my.site.com/search.cgi</link>
</textinput>
</channel>
</rss>
]]>
Example 3 - International
<![CDATA[<?xml version="1.0" encoding="EuC-JP"?>
<!DOCTYPE rss SYSTEM "http://my.netscape.com/publish/formats/rss-0.91.dtd">
<rss version="0.91">
<channel>
<title>本日のトップニュース</title>
<link>http://www.mozilla.org</link>
<description>本日のトップニュース</description>
<language>ja</language> <!-- tagged as Japanese content -->
<item>
<title>NY株、終値は15285.25ドル。インターネット株は依然高値。</title>
<link>http://www.mozilla.org/status/</link>
<description>This is an item description...</description>
</item>
<item>
<title>梅雨前線が活発化。西日本に大雨注意報発令。</title>
<link>http://www.mozilla.org/status/</link>
<description>This is an item description...</description>
</item>
<item>
<title>石川都知事、施設方針演説で、税対策を明言。</title>
<link>http://www.mozilla.org/status/</link>
<description>This is an item description...</description>
</item>
<item>
<title>2000年問題、企業の取り組みが本格化。中間報告発表。</title>
<link>http://www.mozilla.org/status/</link>
<description>This is an item description...</description>
</item>
</channel>
</rss>
]]>
Supported languages
Why these?
These are the language codes that are accepted by Netcenter. Other language
codes may be available as
specified by the w3c, but these are
guaranteed to work with most browsers. Netcenter will currently reject other
language codes, however other sites may accept them.
Codes
af # Afrikaans
sq # Albanian
eu # Basque
be # Belarusian
bg # Bulgarian
ca # Catalan
zh-cn # Chinese (Simplified)
zh-tw # Chinese (Traditional)
hr # Croatian
cs # Czech
da # Danish
nl # Dutch
nl-be # Dutch (Belgium)
nl-nl # Dutch (Netherlands)
en # English
en-au # English (Australia)
en-bz # English (Belize)
en-ca # English (Canada)
en-ie # English (Ireland)
en-jm # English (Jamaica)
en-nz # English (New Zealand)
en-ph # English (Phillipines)
en-za # English (South Africa)
en-tt # English (Trinidad)
en-gb # English (United Kingdom)
en-us # English (United States)
en-zw # English (Zimbabwe)
fo # Faeroese
fi # Finnish
fr # French
fr-be # French (Belgium)
fr-ca # French (Canada)
fr-fr # French (France)
fr-lu # French (Luxembourg)
fr-mc # French (Monaco)
fr-ch # French (Switzerland)
gl # Galician
gd # Gaelic
de # German
de-at # German (Austria)
de-de # German (Germany)
de-li # German (Liechtenstein)
de-lu # German (Luxembourg)
de-ch # German (Switzerland)
el # Greek
hu # Hungarian
is # Icelandic
id # Indonesian
ga # Irish
it # Italian
it-it # Italian (Italy)
it-ch # Italian (Switzerland)
ja # Japanese
ko # Korean
mk # Macedonian
no # Norwegian
pl # Polish
pt # Portuguese
pt-br # Portuguese (Brazil)
pt-pt # Portuguese (Portugal)
ro # Romanian
ro-mo # Romanian (Moldova)
ro-ro # Romanian (Romania)
ru # Russian
ru-mo # Russian (Moldova)
ru-ru # Russian (Russia)
sr # Serbian
sk # Slovak
sl # Slovenian
es # Spanish
es-ar # Spanish (Argentina)
es-bo # Spanish (Bolivia)
es-cl # Spanish (Chile)
es-co # Spanish (Colombia)
es-cr # Spanish (Costa Rica)
es-do # Spanish (Dominican Republic)
es-ec # Spanish (Ecuador)
es-sv # Spanish (El Salvador)
es-gt # Spanish (Guatemala)
es-hn # Spanish (Honduras)
es-mx # Spanish (Mexico)
es-ni # Spanish (Nicaragua)
es-pa # Spanish (Panama)
es-py # Spanish (Paraguay)
es-pe # Spanish (Peru)
es-pr # Spanish (Puerto Rico)
es-es # Spanish (Spain)
es-uy # Spanish (Uruguay)
es-ve # Spanish (Venezuela)
sv # Swedish
sv-fi # Swedish (Finland)
sv-se # Swedish (Sweden)
tr # Turkish
uk # Ukranian
Supported encodings
Note: these are not case sensitive
| IANA standard name |
MIME prefered name (if different from IANA) |
| ANSI_X3.4-1968 |
US-ASCII |
| ISO_8859-1:1987 |
ISO-8859-1 |
| ISO_8859-2:1987 |
ISO-8859-2 |
| ISO_8859-5:1988 |
ISO-8859-5 |
| ISO_8859-7:1987 |
ISO-8859-7 |
| ISO_8859-9:1989 |
ISO-8859-9 |
| Shift_JIS |
| Extended_UNIX_Code_Packed_Format_for_Japanese |
EUC-JP |
| GB2312 |
| EUC-KR |
| Big5 |
| windows-1250 |
| windows-1251 |
| UTF-8 |
| x-mac-roman |
DTD
Location
Public ID: -//Netscape Communications//DTD RSS
0.91//EN
System ID: http://my.netscape.com/publish/formats/rss-0.91.dtd
The DTD itself
<![CDATA[<!--
Rich Site Summary (RSS) 0.91 official DTD, proposed.
RSS is an XML vocabulary for describing
metadata about websites, and enabling the display of
"channels" on the "My Netscape" website.
RSS Info can be found at http://my.netscape.com/publish/
XML Info can be found at http://www.w3.org/XML/
copyright Netscape Communications, 1999
Dan Libby - danda@netscape.com
Based on RSS DTD originally created by
Lars Marius Garshol - larsga@ifi.uio.no.
$Id: rss-spec-0.91.html,v 1.1.4.1 2001/05/03 00:48:22 hoangtv Exp $
-->
<!ELEMENT rss (channel)>
<!ATTLIST rss
version CDATA #REQUIRED> <!-- must be "0.91"> -->
<!ELEMENT channel (title | description | link | language | item+ | rating? | image? | textinput? | copyright? | pubDate? | lastBuildDate? | docs? | managingEditor? | webMaster? | skipHours? | skipDays?)*>
<!ELEMENT title (#PCDATA)>
<!ELEMENT description (#PCDATA)>
<!ELEMENT link (#PCDATA)>
<!ELEMENT image (title | url | link | width? | height? | description?)*>
<!ELEMENT url (#PCDATA)>
<!ELEMENT item (title | link | description)*>
<!ELEMENT textinput (title | description | name | link)*>
<!ELEMENT name (#PCDATA)>
<!ELEMENT rating (#PCDATA)>
<!ELEMENT language (#PCDATA)>
<!ELEMENT width (#PCDATA)>
<!ELEMENT height (#PCDATA)>
<!ELEMENT copyright (#PCDATA)>
<!ELEMENT pubDate (#PCDATA)>
<!ELEMENT lastBuildDate (#PCDATA)>
<!ELEMENT docs (#PCDATA)>
<!ELEMENT managingEditor (#PCDATA)>
<!ELEMENT webMaster (#PCDATA)>
<!ELEMENT hour (#PCDATA)>
<!ELEMENT day (#PCDATA)>
<!ELEMENT skipHours (hour+)>
<!ELEMENT skipDays (day+)>
<!--
Copied from HTML 3.2 DTD, with modifications (removed CDATA)
http://www.w3.org/TR/REC-html32.html#dtd
=============== BEGIN ===================
-->
<!--
Character Entities for ISO Latin-1
(C) International Organization for Standardization 1986
Permission to copy in any form is granted for use with
conforming SGML systems and applications as defined in
ISO 8879, provided this notice is included in all copies.
This has been extended for use with HTML to cover the full
set of codes in the range 160-255 decimal.
-->
<!-- Character entity set. Typical invocation:
<!ENTITY % ISOlat1 PUBLIC
"ISO 8879-1986//ENTITIES Added Latin 1//EN//HTML">
%ISOlat1;
-->
<!ENTITY nbsp " "> <!-- no-break space -->
<!ENTITY iexcl "¡"> <!-- inverted exclamation mark -->
<!ENTITY cent "¢"> <!-- cent sign -->
<!ENTITY pound "£"> <!-- pound sterling sign -->
<!ENTITY curren "¤"> <!-- general currency sign -->
<!ENTITY yen "¥"> <!-- yen sign -->
<!ENTITY brvbar "¦"> <!-- broken (vertical) bar -->
<!ENTITY sect "§"> <!-- section sign -->
<!ENTITY uml "¨"> <!-- umlaut (dieresis) -->
<!ENTITY copy "©"> <!-- copyright sign -->
<!ENTITY ordf "ª"> <!-- ordinal indicator, feminine -->
<!ENTITY laquo "«"> <!-- angle quotation mark, left -->
<!ENTITY not "¬"> <!-- not sign -->
<!ENTITY shy "­"> <!-- soft hyphen -->
<!ENTITY reg "®"> <!-- registered sign -->
<!ENTITY macr "¯"> <!-- macron -->
<!ENTITY deg "°"> <!-- degree sign -->
<!ENTITY plusmn "±"> <!-- plus-or-minus sign -->
<!ENTITY sup2 "²"> <!-- superscript two -->
<!ENTITY sup3 "³"> <!-- superscript three -->
<!ENTITY acute "´"> <!-- acute accent -->
<!ENTITY micro "µ"> <!-- micro sign -->
<!ENTITY para "¶"> <!-- pilcrow (paragraph sign) -->
<!ENTITY middot "·"> <!-- middle dot -->
<!ENTITY cedil "¸"> <!-- cedilla -->
<!ENTITY sup1 "¹"> <!-- superscript one -->
<!ENTITY ordm "º"> <!-- ordinal indicator, masculine -->
<!ENTITY raquo "»"> <!-- angle quotation mark, right -->
<!ENTITY frac14 "¼"> <!-- fraction one-quarter -->
<!ENTITY frac12 "½"> <!-- fraction one-half -->
<!ENTITY frac34 "¾"> <!-- fraction three-quarters -->
<!ENTITY iquest "¿"> <!-- inverted question mark -->
<!ENTITY Agrave "À"> <!-- capital A, grave accent -->
<!ENTITY Aacute "Á"> <!-- capital A, acute accent -->
<!ENTITY Acirc "Â"> <!-- capital A, circumflex accent -->
<!ENTITY Atilde "Ã"> <!-- capital A, tilde -->
<!ENTITY Auml "Ä"> <!-- capital A, dieresis or umlaut mark -->
<!ENTITY Aring "Å"> <!-- capital A, ring -->
<!ENTITY AElig "Æ"> <!-- capital AE diphthong (ligature) -->
<!ENTITY Ccedil "Ç"> <!-- capital C, cedilla -->
<!ENTITY Egrave "È"> <!-- capital E, grave accent -->
<!ENTITY Eacute "É"> <!-- capital E, acute accent -->
<!ENTITY Ecirc "Ê"> <!-- capital E, circumflex accent -->
<!ENTITY Euml "Ë"> <!-- capital E, dieresis or umlaut mark -->
<!ENTITY Igrave "Ì"> <!-- capital I, grave accent -->
<!ENTITY Iacute "Í"> <!-- capital I, acute accent -->
<!ENTITY Icirc "Î"> <!-- capital I, circumflex accent -->
<!ENTITY Iuml "Ï"> <!-- capital I, dieresis or umlaut mark -->
<!ENTITY ETH "Ð"> <!-- capital Eth, Icelandic -->
<!ENTITY Ntilde "Ñ"> <!-- capital N, tilde -->
<!ENTITY Ograve "Ò"> <!-- capital O, grave accent -->
<!ENTITY Oacute "Ó"> <!-- capital O, acute accent -->
<!ENTITY Ocirc "Ô"> <!-- capital O, circumflex accent -->
<!ENTITY Otilde "Õ"> <!-- capital O, tilde -->
<!ENTITY Ouml "Ö"> <!-- capital O, dieresis or umlaut mark -->
<!ENTITY times "×"> <!-- multiply sign -->
<!ENTITY Oslash "Ø"> <!-- capital O, slash -->
<!ENTITY Ugrave "Ù"> <!-- capital U, grave accent -->
<!ENTITY Uacute "Ú"> <!-- capital U, acute accent -->
<!ENTITY Ucirc "Û"> <!-- capital U, circumflex accent -->
<!ENTITY Uuml "Ü"> <!-- capital U, dieresis or umlaut mark -->
<!ENTITY Yacute "Ý"> <!-- capital Y, acute accent -->
<!ENTITY THORN "Þ"> <!-- capital THORN, Icelandic -->
<!ENTITY szlig "ß"> <!-- small sharp s, German (sz ligature) -->
<!ENTITY agrave "à"> <!-- small a, grave accent -->
<!ENTITY aacute "á"> <!-- small a, acute accent -->
<!ENTITY acirc "â"> <!-- small a, circumflex accent -->
<!ENTITY atilde "ã"> <!-- small a, tilde -->
<!ENTITY auml "ä"> <!-- small a, dieresis or umlaut mark -->
<!ENTITY aring "å"> <!-- small a, ring -->
<!ENTITY aelig "æ"> <!-- small ae diphthong (ligature) -->
<!ENTITY ccedil "ç"> <!-- small c, cedilla -->
<!ENTITY egrave "è"> <!-- small e, grave accent -->
<!ENTITY eacute "é"> <!-- small e, acute accent -->
<!ENTITY ecirc "ê"> <!-- small e, circumflex accent -->
<!ENTITY euml "ë"> <!-- small e, dieresis or umlaut mark -->
<!ENTITY igrave "ì"> <!-- small i, grave accent -->
<!ENTITY iacute "í"> <!-- small i, acute accent -->
<!ENTITY icirc "î"> <!-- small i, circumflex accent -->
<!ENTITY iuml "ï"> <!-- small i, dieresis or umlaut mark -->
<!ENTITY eth "ð"> <!-- small eth, Icelandic -->
<!ENTITY ntilde "ñ"> <!-- small n, tilde -->
<!ENTITY ograve "ò"> <!-- small o, grave accent -->
<!ENTITY oacute "ó"> <!-- small o, acute accent -->
<!ENTITY ocirc "ô"> <!-- small o, circumflex accent -->
<!ENTITY otilde "õ"> <!-- small o, tilde -->
<!ENTITY ouml "ö"> <!-- small o, dieresis or umlaut mark -->
<!ENTITY divide "÷"> <!-- divide sign -->
<!ENTITY oslash "ø"> <!-- small o, slash -->
<!ENTITY ugrave "ù"> <!-- small u, grave accent -->
<!ENTITY uacute "ú"> <!-- small u, acute accent -->
<!ENTITY ucirc "û"> <!-- small u, circumflex accent -->
<!ENTITY uuml "ü"> <!-- small u, dieresis or umlaut mark -->
<!ENTITY yacute "ý"> <!-- small y, acute accent -->
<!ENTITY thorn "þ"> <!-- small thorn, Icelandic -->
<!ENTITY yuml "ÿ"> <!-- small y, dieresis or umlaut mark -->
<!--
Copied from HTML 3.2 DTD, with modifications (removed CDATA)
http://www.w3.org/TR/REC-html32.html#dtd
================= END ===================
-->
]]>
Proprietary Schema (Validation Rules)
Explanation
XML currently provides a limited amount of validation via DTD's. However,
DTD's do not provide any support for common validation requirements, such as
data types, length of strings, number of sub-elements, or pattern matching.
A standard has been proposed to solve this problem. XML Schemas looks like it
will do all of this and more. Unfortunately, there are few, if any parsers
available today that understand them.
As a proprietary, interim only solution, we have developed a very
simplistic schema format that performs a second level of validation after the
parser has read the XML document into memory. We are listing the schema used to
validate RSS 0.91 files, so that there will be no ambiguity when validation
fails.
Here are the basic rules:
- Each XML element must be defined by an <Element> tag.
- Each Element definition must have a unique id attribute and a type
attribute.
- Each Attribute of an Element must be referenced by an <Attrib> tag
- Each sub-Element of an Element of type container must be referenced by
<Contains> tag.
- Each Element may have a type associated with it. Currently supported
types are:
- container: this Element contains other Elements only.
- string: this Element contains text data.
- int: this Element contains an integer.
- Each string or int Element may contain a matching rule, specified via
<Matches>
- Each string or int Element may specify a minimum and maximum number of
characters (or value if type int) via min, max, and exactly.
- Each XML attribute must be defined by an <Attribute> tag.
- Each Attribute definition must have a unique id attribute and a type
attribute.
- Each Attribute may be of type string or int.
- Each Attribute may contain a matching rule, specified via
<Matches>
- Each Attribute may specify a minimum and maximum number of characters
(or value if type int) via min, max, and exactly.
- Each <Contains> and <Attrib> definition must contain a 'ref'
attribute that refers to a uniquely defined Element or Attribute with the
value of 'ref' as its id.
- Each <Contains> and <Attrib> definition may contain min, max,
or exactly attributes to define the number of Elements or Attributes required.
- Each <Matches> must contain a valid regular expression, against
which the corresponding Element or Attribute will be evaluated.
Schema
Here is the schema for RSS 0.91.
<![CDATA[<?xml version="1.0"?>
<!DOCTYPE Schema PUBLIC "-//Netscape Communications//DTD Schema 1.0//EN" "http://my.netscape.com/publish/formats/schema-1.0.dtd">
<Schema version="DKHXVF 1.0" root="rss" name="RSS 0.91">
<Element id="rss" type="container">
<Contains ref="channel" exactly="1"/>
<Attrib ref="version" exactly="1"/>
</Element>
<Attribute id="version" type="string">
<Matches>0.91</Matches>
</Attribute>
<Element id="channel" type="container">
<Contains ref="description" exactly="1"/>
<Contains ref="image" min="0" max="1"/>
<Contains ref="item" min="0" max="15"/>
<Contains ref="language" exactly="1"/>
<Contains ref="link" exactly="1"/>
<Contains ref="rating" min="0" max="1"/>
<Contains ref="textinput" min="0" max="1"/>
<Contains ref="title" exactly="1"/>
<Contains ref="copyright" min="0" max="1"/>
<Contains ref="pubDate" min="0" max="1"/>
<Contains ref="lastBuildDate" min="0" max="1"/>
<Contains ref="docs" min="0" max="1"/>
<Contains ref="managingEditor" min="0" max="1"/>
<Contains ref="webMaster" min="0" max="1"/>
<Contains ref="skipHours" min="0" max="1"/>
<Contains ref="skipDays" min="0" max="1"/>
</Element>
<Element id="copyright" type="string" max="100"/>
<Element id="pubDate" type="string" max="100"/>
<Element id="lastBuildDate" type="string" max="100"/>
<Element id="docs" type="string" max="500"/>
<Element id="managingEditor" type="string" max="100"/>
<Element id="webMaster" type="string" max="100"/>
<Element id="skipHours" type="container">
<Contains ref="hour" min="0" max="24"/>
</Element>
<Element id="skipDays" type="container">
<Contains ref="day" min="0" max="7"/>
</Element>
<Element id="hour" type="int" min="0" max="24"/>
<Element id="day" type="string" min="0" max="10"/>
<Element id="item" type="container">
<Contains ref="title" exactly="1"/>
<Contains ref="link" exactly="1"/>
<Contains ref="description" min="0" max="1"/>
</Element>
<Element id="image" type="container">
<Contains ref="title" exactly="1"/>
<Contains ref="link" min="0" max="1" />
<Contains ref="url" exactly="1"/>
<Contains ref="width" min="0" max="1"/>
<Contains ref="height" min="0" max="1"/>
<Contains ref="description" min="0" max="1"/>
</Element>
<Element id="textinput" type="container">
<Contains ref="title" exactly="1"/>
<Contains ref="link" exactly="1"/>
<Contains ref="description" exactly="1"/>
<Contains ref="name" exactly="1"/>
</Element>
<Element id="title" type="string" min="1" max="100"/>
<Element id="description" type="string" min="1" max="500"/>
<Element id="url" type="string" min="1" max="500">
<Matches>^(http://|^ftp://)</Matches>
</Element>
<Element id="link" type="string" min="1" max="500">
<Matches>^(http://|^ftp://)</Matches>
</Element>
<Element id="language" type="string" min="2" max="5">
<Matches>
^(af | # Afrikaans
sq | # Albanian
eu | # Basque
be | # Belarusian
bg | # Bulgarian
ca | # Catalan
zh-cn | # Chinese (Simplified)
zh-tw | # Chinese (Traditional)
hr | # Croatian
cs | # Czech
da | # Danish
nl | # Dutch
nl-be | # Dutch (Belgium)
nl-nl | # Dutch (Netherlands)
en | # English
en-au | # English (Australia)
en-bz | # English (Belize)
en-ca | # English (Canada)
en-ie | # English (Ireland)
en-jm | # English (Jamaica)
en-nz | # English (New Zealand)
en-ph | # English (Phillipines)
en-za | # English (South Africa)
en-tt | # English (Trinidad)
en-gb | # English (United Kingdom)
en-us | # English (United States)
en-zw | # English (Zimbabwe)
fo | # Faeroese
fi | # Finnish
fr | # French
fr-be | # French (Belgium)
fr-ca | # French (Canada)
fr-fr | # French (France)
fr-lu | # French (Luxembourg)
fr-mc | # French (Monaco)
fr-ch | # French (Switzerland)
gl | # Galician
gd | # Gaelic
de | # German
de-at | # German (Austria)
de-de | # German (Germany)
de-li | # German (Liechtenstein)
de-lu | # German (Luxembourg)
de-ch | # German (Switzerland)
el | # Greek
hu | # Hungarian
is | # Icelandic
id | # Indonesian
ga | # Irish
it | # Italian
it-it | # Italian (Italy)
it-ch | # Italian (Switzerland)
ja | # Japanese
ko | # Korean
mk | # Macedonian
no | # Norwegian
pl | # Polish
pt | # Portuguese
pt-br | # Portuguese (Brazil)
pt-pt | # Portuguese (Portugal)
ro | # Romanian
ro-mo | # Romanian (Moldova)
ro-ro | # Romanian (Romania)
ru | # Russian
ru-mo | # Russian (Moldova)
ru-ru | # Russian (Russia)
sr | # Serbian
sk | # Slovak
sl | # Slovenian
es | # Spanish
es-ar | # Spanish (Argentina)
es-bo | # Spanish (Bolivia)
es-cl | # Spanish (Chile)
es-co | # Spanish (Colombia)
es-cr | # Spanish (Costa Rica)
es-do | # Spanish (Dominican Republic)
es-ec | # Spanish (Ecuador)
es-sv | # Spanish (El Salvador)
es-gt | # Spanish (Guatemala)
es-hn | # Spanish (Honduras)
es-mx | # Spanish (Mexico)
es-ni | # Spanish (Nicaragua)
es-pa | # Spanish (Panama)
es-py | # Spanish (Paraguay)
es-pe | # Spanish (Peru)
es-pr | # Spanish (Puerto Rico)
es-es | # Spanish (Spain)
es-uy | # Spanish (Uruguay)
es-ve | # Spanish (Venezuela)
sv | # Swedish
sv-fi | # Swedish (Finland)
sv-se | # Swedish (Sweden)
tr | # Turkish
uk # Ukranian
)$
</Matches>
</Element>
<Element id="rating" type="string" min="20" max="500">
<Matches>^\(PICS-1.1</Matches>
</Element>
<Element id="width" type="int" min="1" max="144"/>
<Element id="height" type="int" min="1" max="400"/>
<Element id="name" type="string" min="1" max="20"/>
</Schema>
]]>
Schema DTD
Here is the DTD for the schema format.
<![CDATA[<!--
A DTD for Dan's Kinda Hacky XML Validation Format (DKHXVF)
Basically, this format allows us to enforce some additional rules
that DTD's do not. Specifically, we can:
- specify min and max for number of each child element
- specify a regular expression that text elements and attributes must match
- specify type of text elements and attributes (int, float, string, timestamp)
- specify min and max for any type. (length compare for strings, numeric otherwise)
The hope is that this will allow the rapid creation of new formats, and modification
of existing formats (adding/removing tags, attributes etc), without requiring
code changes in the validation software.
This is not in any way intended to be an alternative to XML schemas. In the
absence of code supporting XML schemas, I created this, but it is meant as
a transitional work only.
For more on XML schemas, see:
http://www.w3.org/1999/05/06-xmlschema-1/ and
http://www.w3.org/1999/05/06-xmlschema-2/
This is also not meant to replace DTDs. There are many things that you can do
with DTDs that you cannot do with this format. For example, you cannot declare
entities with this format. You must do that in the DTD. If you want your
parser to interpret them correctly, you must use a validating parser.
It is possible to use these schemas without DTD validation, however you may run
into problems with entity expansion and other things.
Dan Libby - danda@netscape.com
$Log: rss-spec-0.91.html,v $
Revision 1.1.4.1 2001/05/03 00:48:22 hoangtv
adding DTD stuff
Revision 1.1.2.1 2001/05/03 00:44:50 hoangtv
adding DTD definition
Revision 1.4 1999/09/10 03:01:44 jquach
removed comments
Revision 1.3 1999/09/10 03:01:24 jquach
pulled ref to internal file
Revision 1.2 1999/08/07 04:53:02 danda
'cleaning' (removing useful info) for public release
Revision 1.3 1999/08/07 04:52:12 danda
'cleaning' (removing useful info) for public release
Revision 1.2 1999/07/22 07:09:41 danda
fixing examples, RDF Site Summary -> Rich Site Summary
Revision 1.1 1999/06/09 07:01:29 danda
adding schema and dtd for rss 0.9 and 1.0
-->
<!--
Tag: Schema
Description: Document wrapper.
Sub tags: Element & Attribute
Attributes: version, root, name
Notes:
version must be "DKHXVF 1.0"
root is the document root.
-->
<!ELEMENT Schema (Element | Attribute)*>
<!ATTLIST Schema
version CDATA #FIXED "DKHXVF 1.0"
root CDATA #REQUIRED
name CDATA #REQUIRED>
<!--
Tag: Element
Description: Definition of an allowed element (tag)
Sub tags: Contains, Attrib, Matches
Attributes: id, type, min, max, exactly
Notes: exactly="1" is equivalent to min="1" max="1"
-->
<!ELEMENT Element ((Contains | Attrib)* | Matches?)>
<!ATTLIST Element
id CDATA #REQUIRED
type (int | float | container | string | timestamp) #REQUIRED
min CDATA #IMPLIED
max CDATA #IMPLIED
exactly CDATA #IMPLIED>
<!--
Tag: Contains
Description: Defines rules for a sub-element.
Sub tags: None, this tag must be empty.
Attributes: ref, min, max, exactly
Notes: ref must refer to the 'id' of an element defined elsewhere or the schema
is invalid.
-->
<!ELEMENT Contains EMPTY>
<!ATTLIST Contains
ref CDATA #REQUIRED
min CDATA #IMPLIED
max CDATA #IMPLIED
exactly CDATA #IMPLIED>
<!--
Tag: Attrib
Description: Defines rules for an element attribute.
Sub tags: None, this tag must be empty
Attributes: ref, min, max, exactly
Notes: ref must refer to the 'id' of an Attribute defined elsewhere or the schema
is invalid.
-->
<!ELEMENT Attrib EMPTY>
<!ATTLIST Attrib
ref CDATA #REQUIRED
min CDATA #IMPLIED
max CDATA #IMPLIED
exactly CDATA #IMPLIED>
<!--
Tag: Attribute
Description: Definition of an allowed attribute
Sub tags: Matches
Attributes: id, type, min, max, exactly
Notes: none
-->
<!ELEMENT Attribute (Matches?)>
<!ATTLIST Attribute
id CDATA #REQUIRED
type (int | float | string | timestamp) #REQUIRED
min CDATA #IMPLIED
max CDATA #IMPLIED
exactly CDATA #IMPLIED>
<!--
Tag: Matches
Description: A regular expression that values will be compared against
Sub tags: None
Attributes: None
Notes: Matches may be used for elements of any type but container, and for attributes.
An example of a useful matching pattern is:
<Matches>^(foo|bar|foobar)$</Matches>
This will allow any values that exactly match "foo", "bar", or "foobar".
Whitespace is allowed in the regex and '#' is used for comments. The following
is valid:
<Matches>
&# # Start of a numeric entity reference, xml escaped &
(?P<char> # xml escaped <, >
[0-9]+[^0-9] # Decimal form
| 0[0-7]+[^0-7] # Octal form
| x[0-9a-fA-F]+[^0-9a-fA-F] # Hexadecimal form
)
</Matches>
which is equivalent to:
<Matches>&#(?P<char>[0-9]+[^0-9]| 0[0-7]+[^0-7]| x[0-9a-fA-F]+[^0-9a-fA-F])</Matches>
For help on regular expressions, see:
http://www.python.org/doc/howto/regex/regex.html or
http://www.ciser.cornell.edu/info/regex.html
-->
<!ELEMENT Matches (#PCDATA)>
<!--
Example of a DKHXVF 1.0 file:
<?xml version="1.0"?>
<!DOCTYPE Schema PUBLIC "-//Netscape Communications//DTD Schema 1.0//EN" "http://my.netscape.com/publish/formats/schema-1.0.dtd">
<Schema version="DKHXVF 1.0" root="rdf:RDF" name="RSS 0.9">
<Element id="rdf:RDF" type="container">
<Contains ref="channel" exactly="1"/>
<Contains ref="image" min="0" max="1"/>
<Contains ref="item" min="1" max="15"/>
<Contains ref="textinput" min="0" max="1"/>
<Attrib ref="xmlns" exactly="1"/>
<Attrib ref="xmlns:rdf" exactly="1"/>
</Element>
<Attribute id="xmlns" type="string">
<Matches>http://my.netscape.com/rdf/simple/0.9/</Matches>
</Attribute>
<Attribute id="xmlns:rdf" type="string">
<Matches>http://www.w3.org/1999/02/22-rdf-syntax-ns#</Matches>
</Attribute>
<Element id="channel" type="container">
<Contains ref="link" exactly="1"/>
<Contains ref="title" exactly="1"/>
<Contains ref="description" exactly="1"/>
</Element>
<Element id="item" type="container">
<Contains ref="title" exactly="1"/>
<Contains ref="link" exactly="1"/>
</Element>
<Element id="image" type="container">
<Contains ref="title" exactly="1"/>
<Contains ref="link" exactly="1" />
<Contains ref="url" exactly="1"/>
</Element>
<Element id="textinput" type="container">
<Contains ref="title" exactly="1"/>
<Contains ref="description" exactly="1"/>
<Contains ref="link" exactly="1"/>
<Contains ref="name" exactly="1"/>
</Element>
<Element id="title" type="string" min="1" max="100"/>
<Element id="description" type="string" min="1" max="500"/>
<Element id="url" type="string" min="1" max="500">
<Matches>^(http://|^ftp://)</Matches>
</Element>
<Element id="link" type="string" min="1" max="500">
<Matches>^(http://|^ftp://)</Matches>
</Element>
<Element id="name" type="string" min="1" max="20"/>
</Schema>
-->
]]>