Network Working Group A. Bryan, Ed.
Internet-Draft Metalinker Project
Intended status: Experimental September 4, 2008
Expires: March 8, 2009
The Metalink Download Description Format
draft-bryan-metalink-02
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Abstract
This document specifies Metalink Documents, an XML-based download
description format.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Namespace and Version . . . . . . . . . . . . . . . . . . 5
1.3. Notational Conventions . . . . . . . . . . . . . . . . . . 5
2. Metalink Documents . . . . . . . . . . . . . . . . . . . . . . 6
3. Common Metalink Constructs . . . . . . . . . . . . . . . . . . 7
3.1. Text Constructs . . . . . . . . . . . . . . . . . . . . . 7
3.1.1. Text . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2. Date Constructs . . . . . . . . . . . . . . . . . . . . . 8
4. Metalink Element Definitions . . . . . . . . . . . . . . . . . 8
4.1. Container Elements . . . . . . . . . . . . . . . . . . . . 8
4.1.1. The "metalink:metalink" Element . . . . . . . . . . . 9
4.1.2. The "metalink:files" Element . . . . . . . . . . . . . 10
4.1.3. The "metalink:file" Element . . . . . . . . . . . . . 11
4.1.4. The "metalink:resources" Element . . . . . . . . . . . 12
4.1.5. The "metalink:verification" Element . . . . . . . . . 13
4.1.6. The "metalink:pieces" Element . . . . . . . . . . . . 13
4.2. Metadata Elements . . . . . . . . . . . . . . . . . . . . 14
4.2.1. The "metalink:copyright" Element . . . . . . . . . . . 14
4.2.2. The "metalink:description" Element . . . . . . . . . . 14
4.2.3. The "metalink:generator" Element . . . . . . . . . . . 14
4.2.4. The "metalink:hash" Element . . . . . . . . . . . . . 15
4.2.5. The "metalink:identity" Element . . . . . . . . . . . 16
4.2.6. The "metalink:language" Element . . . . . . . . . . . 16
4.2.7. The "metalink:license" Element . . . . . . . . . . . . 16
4.2.8. The "metalink:logo" Element . . . . . . . . . . . . . 17
4.2.9. The "metalink:metadata" Element . . . . . . . . . . . 17
4.2.10. The "metalink:origin" Element . . . . . . . . . . . . 18
4.2.11. The "metalink:os" Element . . . . . . . . . . . . . . 18
4.2.12. The "metalink:published" Element . . . . . . . . . . . 18
4.2.13. The "metalink:publisher" Element . . . . . . . . . . . 18
4.2.14. The "metalink:signature" Element . . . . . . . . . . . 19
4.2.15. The "metalink:size" Element . . . . . . . . . . . . . 19
4.2.16. The "metalink:type" Element . . . . . . . . . . . . . 19
4.2.17. The "metalink:updated" Element . . . . . . . . . . . . 20
4.2.18. The "metalink:url" Element . . . . . . . . . . . . . . 20
4.2.19. The "metalink:version" Element . . . . . . . . . . . . 21
5. Securing Metalink Documents . . . . . . . . . . . . . . . . . 21
5.1. Digital Signatures . . . . . . . . . . . . . . . . . . . . 21
5.2. Encryption . . . . . . . . . . . . . . . . . . . . . . . . 22
5.3. Signing and Encrypting . . . . . . . . . . . . . . . . . . 23
6. Extending Metalink . . . . . . . . . . . . . . . . . . . . . . 23
6.1. Extensions from Non-Metalink Vocabularies . . . . . . . . 23
6.2. Extensions to the Metalink Vocabulary . . . . . . . . . . 23
6.3. Processing Foreign Markup . . . . . . . . . . . . . . . . 23
6.4. Extension Elements . . . . . . . . . . . . . . . . . . . . 24
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6.4.1. Simple Extension Elements . . . . . . . . . . . . . . 24
6.4.2. Structured Extension Elements . . . . . . . . . . . . 24
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
8. Security Considerations . . . . . . . . . . . . . . . . . . . 26
8.1. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
8.2. IRIs . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
8.3. Spoofing . . . . . . . . . . . . . . . . . . . . . . . . . 26
8.4. Encryption and Signing . . . . . . . . . . . . . . . . . . 26
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 26
9.1. Normative References . . . . . . . . . . . . . . . . . . . 26
9.2. Informative References . . . . . . . . . . . . . . . . . . 28
Appendix A. Contributors . . . . . . . . . . . . . . . . . . . . 29
Appendix B. RELAX NG Compact Schema . . . . . . . . . . . . . . . 30
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 36
Intellectual Property and Copyright Statements . . . . . . . . . . 37
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1. Introduction
Metalink is an XML-based document format that describes a file or
lists of files to be added to a download queue. Lists are composed
of a number of files, each with an extensible set of attached
metadata. For example, each file can have a description, checksum,
and list of URIs that it is available from.
The primary use case that Metalink addresses is the description of
downloadable content in a format so download agents can act
intelligently and recover from common errors with little or no user
interaction necessary. These errors can include multiple servers
going down and data corrupted in transmission.
1.1. Examples
A brief, single file Metalink Document:
<?xml version="1.0" encoding="UTF-8"?>
<metalink xmlns="http://www.metalinker.org">
<files>
<file name="example.ext">
<resources>
<url>ftp://ftp.example.com/example.ext</url>
<url>http://example.com/example.ext</url>
<metadata type="torrent">
http://example.com/example.ext.torrent
</metadata>
</resources>
</file>
</files>
</metalink>
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A more extensive, single file Metalink Document:
<?xml version="1.0" encoding="UTF-8"?>
<metalink xmlns="http://www.metalinker.org">
<published>2008-05-15T12:23:23Z</published>
<files>
<file name="example.ext">
<identity>Example</identity>
<version>1.0</version>
<description>A description of the example file for
download.</description>
<verification>
<hash type="md5">83b1a04f18d6782cfe0407edadac377f</hash>
<hash type="sha-1">80bc95fd391772fa61c91ed68567f0980bb45fd9
</hash>
</verification>
<resources>
<url>ftp://ftp.example.com/example.ext</url>
<url>http://example.com/example.ext</url>
<metadata type="torrent">
http://example.com/example.ext.torrent
</metadata>
</resources>
</file>
</files>
</metalink>
1.2. Namespace and Version
The XML Namespaces URI [REC-xml-names] for the XML data format
described in this specification is:
http://www.metalinker.org/
For convenience, this data format may be referred to as "Metalink",
which this specification uses internally.
1.3. Notational Conventions
This specification describes conformance of Metalink Documents.
Additionally, it places some requirements on Metalink Processors.
This specification uses the namespace prefix "metalink:" for the
Namespace URI identified in Section 1.2, above. Note that the choice
of namespace prefix is arbitrary and not semantically significant.
Metalink is specified using terms from the XML Infoset
[REC-xml-infoset]. However, this specification uses a shorthand for
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two common terms: the phrase "Information Item" is omitted when
naming Element Information Items and Attribute Information Items.
Therefore, when this specification uses the term "element," it is
referring to an Element Information Item in Infoset terms. Likewise,
when it uses the term "attribute," it is referring to an Attribute
Information Item.
Some sections of this specification are illustrated with fragments of
a non-normative RELAX NG Compact schema [RELAX-NG]. However, the
text of this specification provides the definition of conformance. A
complete schema appears in Appendix B.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14, [RFC2119], as
scoped to those conformance targets.
2. Metalink Documents
This specification describes Metalink Documents.
A Metalink Document describes a file or group of files, how to access
them, and metadata that identifies them. Its root is the metalink:
metalink element.
namespace metalink = "http://www.metalinker.org"
start = metalinkMetalink
Metalink Documents are specified in terms of the XML Information Set,
serialized as XML 1.0 [REC-xml] and identified with the "application/
metalink+xml" media type. Metalink Documents MUST be well-formed
XML. This specification does not define a DTD for Metalink
Documents, and hence does not require them to be valid (in the sense
used by XML).
Metalink allows the use of IRIs [RFC3987]. Every URI [RFC3986] is
also an IRI, so a URI may be used wherever below an IRI is named.
There is one special consideration: when an IRI that is not also a
URI is given for dereferencing, it MUST be mapped to a URI using the
steps in Section 3.1 of [RFC3987].
Any element defined by this specification MAY have an xml:base
attribute [REC-xmlbase]. When xml:base is used in an Metalink
Document, it serves the function described in Section 5.1.1 of
[RFC3986], establishing the base URI (or IRI) for resolving any
relative references found within the effective scope of the xml:base
attribute.
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Any element defined by this specification MAY have an xml:lang
attribute, whose content indicates the natural language for the
element and its descendents. The language context is only
significant for elements and attributes declared to be "Language-
Sensitive" by this specification. Requirements regarding the content
and interpretation of xml:lang are specified in XML 1.0 [REC-xml],
Section 2.12.
metalinkCommonAttributes =
attribute xml:base { metalinkUri }?,
attribute xml:lang { metalinkLanguageTag }?,
undefinedAttribute*
Metalink is an extensible format. See Section 6 of this document for
a full description of how Metalink Documents can be extended.
3. Common Metalink Constructs
Many of Metalink's elements share a few common structures. This
section defines those structures and their requirements for
convenient reference by the appropriate element definitions.
When an element is identified as being a particular kind of
construct, it inherits the corresponding requirements from that
construct's definition in this section.
Note that there MUST NOT be any white space in a Date construct or in
any IRI. Some XML-emitting implementations erroneously insert white
space around values by default, and such implementations will emit
invalid Metalink Documents.
3.1. Text Constructs
A Text construct contains human-readable text, usually in small
quantities. The content of Text constructs is Language-Sensitive.
metalinkTextConstruct =
metalinkCommonAttributes,
text
3.1.1. Text
Example metalink:description with text content:
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...
<description>
A description of the example file for download.
</description>
...
The content of the Text construct MUST NOT contain child elements.
Such text is intended to be presented to humans in a readable
fashion. Thus, Metalink Processors MAY collapse white space
(including line breaks) and display the text using typographic
techniques such as justification and proportional fonts.
3.2. Date Constructs
A Date construct is an element whose content MUST conform to the
"date-time" production in [RFC3339]. In addition, an uppercase "T"
character MUST be used to separate date and time, and an uppercase
"Z" character MUST be present in the absence of a numeric time zone
offset.
metalinkDateConstruct =
metalinkCommonAttributes,
xsd:dateTime
Such date values happen to be compatible with the following
specifications: [ISO.8601.1988], [W3C.NOTE-datetime-19980827], and
[W3C.REC-xmlschema-2-20041028].
Example Date constructs:
<updated>2008-12-13T18:30:02Z</updated>
<updated>2008-12-13T18:30:02.25Z</updated>
<updated>2008-12-13T18:30:02+01:00</updated>
<updated>2008-12-13T18:30:02.25+01:00</updated>
Date values SHOULD be as accurate as possible. For example, it would
be generally inappropriate for a publishing system to apply the same
timestamp to several entries that were published during the course of
a single day.
4. Metalink Element Definitions
4.1. Container Elements
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4.1.1. The "metalink:metalink" Element
The "metalink:metalink" element is the document (i.e., top-level)
element of a Metalink Document, acting as a container for metadata
and data associated with the listed files. It contains one
"metalink:files" element whose element children consist of metadata
elements followed by one or more metalink:file child elements.
metalinkMetalink =
element metalink:metalink {
metalinkCommonAttributes,
(metalinkPublished?
& metalinkOrigin?
& metalinkGenerator?
& metalinkUpdated?
& extensionElement*),
metalinkFiles
}
The following child elements are defined by this specification (note
that the presence of some of these elements is required):
o metalink:metalink elements MUST contain exactly one metalink:files
element.
o metalink:metalink elements MAY contain exactly one metalink:origin
element. If metalink:type is "dynamic", metalink:metalink
elements MUST contain exactly one metalink:origin element.
o metalink:metalink elements MAY contain exactly one metalink:type
element.
o metalink:metalink elements MAY contain exactly one metalink:
generator element.
o metalink:metalink elements MAY contain exactly one metalink:
published element.
o metalink:metalink elements MAY contain exactly one metalink:
updated element. If metalink:type is "dynamic", metalink:metalink
elements MUST contain exactly one metalink:updated element.
4.1.1.1. Providing Textual Content
Experience teaches that downloads providing textual content are in
general more useful than those that do not. Some applications (one
example is full-text indexers) require a minimum amount of text to
function reliably and predictably. Metalink publishers should be
aware of these issues. It is advisable that each metalink:file
element contain a non-empty metalink:description element, a non-empty
metalink:identity element when that element is present, and a non-
empty metalink:version element, and a non-empty metalink:publisher
element. However, the absence of metalink:description is not an
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error, and Metalink Processors MUST NOT fail to function correctly as
a consequence of such an absence.
4.1.2. The "metalink:files" Element
The "metalink:files" element acts as a container for metadata and
data associated with the listed files. It contains one or more
metalink:file child elements. Certain elements can be listed either
under metalink:files or metalink:file. If under metalink:files, they
apply to all files listed in each metalink:file. If under metalink:
file, then they apply to just that specific file.
metalinkFiles =
element metalink:files {
metalinkCommonAttributes,
(metalinkIdentity?
& metalinkVersion?
& metalinkDescription?
& metalinkOS?
& metalinkLogo?
& metalinkLanguage?
& metalinkPublisher?
& metalinkCopyright?
& metalinkLicense?
& extensionElement*)
metalinkFile
}
The following child elements are defined by this specification (note
that the presence of some of these elements is required):
o metalink:files element MUST contain one or more metalink:file
elements.
o metalink:files elements SHOULD contain exactly one metalink:
identity element.
o metalink:files elements SHOULD contain exactly one metalink:
version element.
o metalink:files elements MAY contain exactly one metalink:
description element.
o metalink:files elements MAY contain exactly one metalink:os
element.
o metalink:files elements MAY contain exactly one metalink:logo
element.
o metalink:files elements MAY contain exactly one metalink:language
element.
o metalink:files elements MAY contain exactly one metalink:publisher
element.
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o metalink:files elements MAY contain exactly one metalink:copyright
element.
o metalink:files elements MAY contain exactly one metalink:license
element.
4.1.3. The "metalink:file" Element
The "metalink:file" element represents an individual file, acting as
a container for metadata and data associated with the file.
metalinkFile =
element metalink:file {
metalinkCommonAttributes,
attribute name { metalinkTextConstruct },
(metalinkVerification?
& metalinkIdentity?
& metalinkVersion?
& metalinkDescription?
& metalinkSize?
& metalinkOS?
& metalinkLogo?
& metalinkLanguage?
& metalinkPublisher?
& metalinkCopyright?
& metalinkLicense?
& extensionElement*)
metalinkResources
}
This specification assigns no significance to the order of metalink:
file elements.
The following child elements are defined by this specification (note
that it requires the presence of some of these elements):
o metalink:file elements MUST contain exactly one metalink:resources
element.
o metalink:file elements SHOULD contain exactly one metalink:
verification element.
o metalink:file elements SHOULD contain exactly one metalink:
identity element.
o metalink:file elements SHOULD contain exactly one metalink:version
element.
o metalink:file elements MAY contain exactly one metalink:
description element.
o metalink:file elements SHOULD contain exactly one metalink:size
element.
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o metalink:file elements MAY contain exactly one metalink:os
element.
o metalink:file elements MAY contain exactly one metalink:logo
element.
o metalink:file elements MAY contain exactly one metalink:language
element.
o metalink:file elements MAY contain exactly one metalink:publisher
element.
o metalink:file elements MAY contain exactly one metalink:copyright
element.
o metalink:file elements MAY contain exactly one metalink:license
element.
4.1.3.1. The "name" Attribute
metalink:file elements MUST have a "name" attribute, which contains
the filename of the file downloaded.
Directory information can also be contained in a "path/file" format
only, as in:
<file name="debian-amd64/sarge/Contents-amd64.gz">
In this example, a subdirectory debian-amd64/sarge/ will be created
and a file named Contents-amd64.gz will be created inside it. The
path MUST be relative. The path MUST NOT begin with a "/", "./" or
"../", contain "/../", or end with "/..". Metalink Processors MUST
NOT allow directory traversal.
A Metalink Processor MAY alter the name of the subdirectory or file
if they contain characters which are invalid in the destination
filesystem.
4.1.4. The "metalink:resources" Element
The "metalink:resources" element acts as a container for metadata and
data associated with the listed files. It contains one or more
metalink:url child elements.
metalinkResources =
element metalink:resources {
metalinkCommonAttributes,
extensionElement*
metalinkURL*
}
This specification assigns no significance to the order of metalink:
url elements. Significance is determined by the value of the
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"preference" attribute of the metalink:url elements.
The following child elements are defined by this specification (note
that the presence of some of these elements is required):
o metalink:resources element MAY contain at least one metalink:
metadata element.
o metalink:resources element MUST contain at least one metalink:url
element. Typically, such elements contain more than one metalink:
url element to provide multiple download sources.
4.1.5. The "metalink:verification" Element
The "metalink:verification" element acts as a container for metadata
and data associated with verifying the listed files. This
information is in the form of checksums and digital signatures.
Checksums are used to verify the integrity of a file or portion of a
file to determine if the files have been transferred without any
errors. Digital signatures verify that a file is from the entity
that has signed it.
metalinkVerification =
element metalink:verification {
metalinkCommonAttributes,
(metalinkHash*
& metalinkPieces*
& metalinkSignature
& extensionElement*)
}
The following child elements are defined by this specification (note
that the presence of some of these elements is required):
o metalink:verification element MAY contain one or more metalink:
hash elements.
o metalink:verification element MAY contain one or more metalink:
pieces elements.
o metalink:verification element MAY contain exactly one metalink:
signature elements.
4.1.6. The "metalink:pieces" Element
The "metalink:pieces" element is a Text construct that conveys a
human-readable piece information for a file.
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metalinkPieces =
element metalink:pieces {
attribute length { metalinkTextConstruct },
attribute type { metalinkTextConstruct },
hash+
}+,
4.1.6.1. The "type" Attribute
metalink:pieces elements MUST have a "type" attribute.
The IANA registry named "Hash Function Textual Names" defines values
for hash types.
4.1.6.2. The "length" Attribute
metalink:pieces elements MUST have a "length" attribute, which is an
integer that describes the length of the piece of the file in octets.
4.2. Metadata Elements
4.2.1. The "metalink:copyright" Element
The "metalink:copyright" element is a Text construct that conveys a
human-readable copyright for a file.
metalinkCopyright =
element metalink:copyright {
metalinkTextConstruct
}
4.2.2. The "metalink:description" Element
The "metalink:description" element is a Text construct that conveys a
human-readable description for a file.
metalinkDescription =
element metalink:description {
metalinkTextConstruct
}
4.2.3. The "metalink:generator" Element
The "metalink:generator" element's content identifies the agent used
to generate a Metalink Document, for debugging and other purposes.
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metalinkGenerator = element metalink:generator {
metalinkCommonAttributes,
attribute uri { metalinkUri }?,
attribute version { text }?,
text
}
The content of this element, when present, MUST be a string that is a
human-readable name for the generating agent. Entities such as
"&" and "<" represent their corresponding characters ("&" and
"<" respectively), not markup.
The metalink:generator element MAY have a "uri" attribute whose value
MUST be an IRI reference [RFC3987]. When dereferenced, the resulting
URI (mapped from an IRI, if necessary) SHOULD produce a
representation that is relevant to that agent.
The metalink:generator element MAY have a "version" attribute that
indicates the version of the generating agent.
4.2.4. The "metalink:hash" Element
The "metalink:hash" element is a Text construct that conveys a human-
readable hash for a file.
metalinkHash =
element metalink:hash {
attribute piece { xsd:integer }?,
attribute type { metalinkTextConstruct },
text
}
4.2.4.1. The "type" Attribute
metalink:hash elements MUST have a "type" attribute or a "piece"
attribute. metalink:hash elements with a "type" attribute contain a
hash of the whole file. metalink:hash elements with a "piece"
attribute contain a hash for that specific piece or chunk of the
file. All hashes are in lowercase hexadecimal format.
When multiple hash types methods are provided, a Metalink Processor
MAY verify using more than one of these hash types. Metalink
Processors are encouraged to check all hash types given which they
are able to process.
The IANA registry named "Hash Function Textual Names" defines values
for hash types.
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4.2.4.2. The "piece" Attribute
metalink:hash elements MAY have a "piece" attribute, only when they
are a sub element of metalink:pieces. The value of "piece" starts at
"0" and increases, depending on the "length" attribute of metalink:
pieces and the size of the file.
4.2.5. The "metalink:identity" Element
The "metalink:identity" element is a Text construct that conveys a
human-readable identity for a file. The identity of OpenOffice.org
3.0 would be "OpenOffice.org".
metalinkIdentity =
element metalink:identity {
metalinkTextConstruct
}
4.2.6. The "metalink:language" Element
The "metalink:language" element is a Text construct that conveys a
code for the language of a file, per [ISO639-2].
metalinkLanguage =
element metalink:language {
metalinkTextConstruct
}
4.2.7. The "metalink:license" Element
The "metalink:license" element is a Text construct that conveys a
human-readable license name for a file.
metalinkLicense =
element metalink:license {
metalinkCommonAttributes,
attribute uri { metalinkUri }?,
attribute name { metalinkTextConstruct }?,
}
The metalink:license element MAY have a "uri" attribute whose value
MUST be an IRI reference [RFC3987]. When dereferenced, the resulting
URI (mapped from an IRI, if necessary) SHOULD produce a
representation that is relevant to that agent.
The metalink:license element MAY have a "name" attribute that
indicates the name of the license.
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4.2.8. The "metalink:logo" Element
The "metalink:logo" element's content is an IRI reference [RFC3987]
that identifies an image that provides visual identification for a
file.
metalinkLogo = element metalink:logo {
metalinkCommonAttributes,
(metalinkUri)
}
The image SHOULD have an aspect ratio of one (horizontal) to one
(vertical) and SHOULD be suitable for presentation at a small size.
4.2.9. The "metalink:metadata" Element
The "metalink:metadata" element contains the IRI of metadata about a
resource to download. For example, this could be the IRI of a
BitTorrent .torrent file or a Metalink Document.
metalinkMetadata =
element metalink:metadata {
metalinkCommonAttributes,
attribute preference { xsd:integer }?,
attribute type { metalinkTextConstruct },
metalinkUri
}+
4.2.9.1. The "preference" Attribute
metalink:metadata elements MAY have a preference attribute, whose
value MUST be a number from 1 to 100 for priority, with 100 used
first and 1 used last. See the "preference" attribute of the
metalink:url element for more information.
4.2.9.2. The "type" Attribute
metalink:metadata elements MUST have a "type" attribute that
indicates the MIME type of the metadata available at the IRI. In the
case of BitTorrent as specified in [BITTORRENT], the value "torrent"
is required. Types without "/" are reserved. Currently, "torrent"
is the only reserved value.
Metalink Processors that do not support a specified type of metadata
about a resource to download MUST ignore that metadata.
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4.2.10. The "metalink:origin" Element
The "metalink:origin" element is an IRI where the Metalink Document
was originally published. If metalink:type is "dynamic", then
updated versions of the Metalink can be found at this IRI.
metalinkOrigin = element metalink:origin {
metalinkCommonAttributes,
(metalinkUri)
}
4.2.11. The "metalink:os" Element
The "metalink:os" element is a Text construct that conveys a human-
readable Operating System for a file.
metalinkOS =
element metalink:os {
metalinkTextConstruct
}
4.2.12. The "metalink:published" Element
The "metalink:published" element is a Date construct indicating an
instant in time associated with an event early in the life cycle of
the entry.
metalinkPublished =
element metalink:published {
metalinkDateConstruct
}
Typically, metalink:published will be associated with the initial
creation or first availability of the resource.
4.2.13. The "metalink:publisher" Element
The "metalink:publisher" element indicates a group or other entity
which has published the file.
metalinkPublisher =
element metalink:publisher {
metalinkCommonAttributes,
attribute uri { metalinkUri }?,
attribute name { metalinkTextConstruct }?,
}
The metalink:publisher element MAY have a "uri" attribute whose value
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MUST be an IRI reference [RFC3987]. When dereferenced, the resulting
URI (mapped from an IRI, if necessary) SHOULD produce a
representation that is relevant to that agent.
The metalink:publisher element MAY have a "name" attribute that
indicates the name of the publisher.
4.2.14. The "metalink:signature" Element
The "metalink:signature" element is a Text construct that conveys a
digital signature for a file described in a Metalink Document.
metalinkSignature =
element metalink:signature {
attribute type { "pgp" },
metalinkTextConstruct
}
4.2.14.1. The "type" Attribute
metalink:signature elements MUST have a "type" attribute. The inital
value of "type" is the string that is non-empty and matches "pgp".
It may be useful to extend Metalink documents with new types of
digital signatures, so unknown types are allowed.
4.2.15. The "metalink:size" Element
The "metalink:size" element indicates the length of the linked
content in octets; it is a hint about the content length of the
representation returned when the IRI is mapped to a URI and
dereferenced. Note that the "metalink:size" element MUST override
the actual content length of the representation as reported by the
underlying protocol, i.e. files with different sizes should be
discarded.
metalinkSize =
element metalink:size {
metalinkTextConstruct
}
4.2.16. The "metalink:type" Element
The "metalink:type" element is a Text construct that describes
whether the IRI from "metalink:origin" a Metalink will contain
dynamic updated Metalinks or static content that is not updated.
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metalinkType =
element metalink:type {
"static" | "dynamic"
}
4.2.17. The "metalink:updated" Element
The "metalink:updated" element is a Date construct indicating the
most recent instant in time when a Metalink was modified in a way the
publisher considers significant. Therefore, not all modifications
necessarily result in a changed metalink:updated value.
metalinkUpdated =
element metalink:updated {
metalinkDateConstruct
}
Publishers MAY change the value of this element over time.
4.2.18. The "metalink:url" Element
The "metalink:url" element contains the IRI of a file. All IRIs MUST
lead to identical files.
metalinkURL =
element metalink:url {
metalinkCommonAttributes,
attribute location { xsd:string {
minLength = "2" maxLength="2"}
}?,
attribute preference { xsd:integer }?,
metalinkUri
}+
4.2.18.1. The "preference" Attribute
metalink:url elements MAY have a preference attribute, whose value
MUST be a number from 1 to 100 for priority, with 100 used first and
1 used last. Multiple metalink:url elements can have the same
preference, i.e. ten mirrors could have preference="100". A Metalink
Processor MAY download different segments of a file from more than
one IRI simultaneously, and when doing so SHOULD first use the
highest priority IRIs and then use lower ones.
When one or more metalink:url elements have a preference attribute
value of "100", other metalink:url elements SHOULD NOT be used,
unless the elements with a preference of 100 cannot be processed
(e.g. if they are of a metalink:metadata element type which is not
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supported by the Metalink Processor, such as BitTorrent, or if the
servers are unavailable).
Any metalink:url elements with a preference attribute value of "1"
SHOULD NOT be used unless all other metalink:url elements cannot be
processed (e.g. are "bittorrent" etc and this is not supported by the
Metalink Processor, or the servers are down).
4.2.18.2. The "location" Attribute
metalink:url elements MAY have a "location" attribute, which is a
[ISO3166] alpha-2 two letter country code for the geographical
location of the physical server an IRI is used to access.
4.2.19. The "metalink:version" Element
The "metalink:version" element is a Text construct that conveys a
human-readable version for a file. The version of OpenOffice.org 3.0
would be "3.0".
metalinkVersion =
element metalink:version {
metalinkTextConstruct
}
5. Securing Metalink Documents
Because Metalink is an XML-based format, existing XML security
mechanisms can be used to secure its content.
Producers of Metalinks may have sound reasons for signing and/or
encrypting otherwise-unprotected content. For example, a merchant
might digitally sign a Metalink that lists a file download to verify
its origin. Other merchants may wish to sign and encypt Metalinks
that list digital songs that have been purchased. Of course, many
other examples exist as well.
The algorithm requirements in this section pertain to the Metalink
Processor. They require that a recipient, at a minimum, be able to
handle messages that use the specified cryptographic algorithms.
These requirements do not limit the algorithms that the sender can
choose.
5.1. Digital Signatures
The root of a Metalink Document (i.e., metalink:metalink MAY have an
Enveloped Signature, as described by XML-Signature and Syntax
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Processing [REC-xmldsig-core].
Metalink Processors MUST NOT reject an Metalink Document containing
such a signature because they are not capable of verifying it; they
MUST continue processing and MAY inform the user of their failure to
validate the signature.
In other words, the presence of an element with the namespace URI
"http://www.w3.org/2000/09/xmldsig#" and a local name of "Signature"
as a child of the document element MUST NOT cause an Metalink
Processor to fail merely because of its presence.
Other elements in an Metalink Document MUST NOT be signed unless
their definitions explicitly specify such a capability.
Section 6.5.1 of [REC-xmldsig-core] requires support for Canonical
XML [REC-xml-c14n]. However, many implementers do not use it because
signed XML documents enclosed in other XML documents have their
signatures broken. Thus, Metalink Processors that verify signed
Metalink Documents MUST be able to canonicalize with the exclusive
XML canonicalization method identified by the URI
"http://www.w3.org/2001/10/xml-exc-c14n#", as specified in Exclusive
XML Canonicalization [REC-xml-exc-c14n].
Section 4.4.2 of [REC-xmldsig-core] requires support for DSA
signatures and recommends support for RSA signatures. However,
because of the much greater popularity in the market of RSA versus
DSA, Metalink Processors that verify signed Metalink Documents MUST
be able to verify RSA signatures, but do not need be able to verify
DSA signatures. Due to security issues that can arise if the keying
material for message authentication code (MAC) authentication is not
handled properly, Metalink Documents SHOULD NOT use MACs for
signatures.
5.2. Encryption
The root of a Metalink Document (i.e., metalink:metalink in a
Metalink Document MAY be encrypted, using the mechanisms described by
XML Encryption Syntax and Processing [REC-xmlenc-core].
Section 5.1 of [REC-xmlenc-core] requires support of TripleDES, AES-
128, and AES-256. Metalink Processors that decrypt Metalink
Documents MUST be able to decrypt with AES-128 in Cipher Block
Chaining (CBC) mode.
Encryption based on [REC-xmlenc-core] does not ensure integrity of
the original document. There are known cryptographic attacks where
someone who cannot decrypt a message can still change bits in a way
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where part or all the decrypted message makes sense but has a
different meaning. Thus, Metalink Processors that decrypt Metalink
Documents SHOULD check the integrity of the decrypted document by
verifying the hash in the signature (if any) in the document, or by
verifying a hash of the document within the document (if any).
5.3. Signing and Encrypting
When an Metalink Document is to be both signed and encrypted, it is
generally a good idea to first sign the document, then encrypt the
signed document. This provides integrity to the base document while
encrypting all the information, including the identity of the entity
that signed the document. Note that, if MACs are used for
authentication, the order MUST be that the document is signed and
then encrypted, and not the other way around.
6. Extending Metalink
6.1. Extensions from Non-Metalink Vocabularies
This specification describes Metalink's XML markup vocabulary.
Markup from other vocabularies ("foreign markup") can be used in an
Metalink Document.
6.2. Extensions to the Metalink Vocabulary
The Metalink namespace is reserved for future forward-compatible
revisions of Metalink. Future versions of this specification could
add new elements and attributes to the Metalink markup vocabulary.
Software written to conform to this version of the specification will
not be able to process such markup correctly and, in fact, will not
be able to distinguish it from markup error. For the purposes of
this discussion, unrecognized markup from the Metalink vocabulary
will be considered "foreign markup".
6.3. Processing Foreign Markup
Metalink Processors that encounter foreign markup in a location that
is legal according to this specification MUST NOT stop processing or
signal an error. It might be the case that the Metalink Processor is
able to process the foreign markup correctly and does so. Otherwise,
such markup is termed "unknown foreign markup".
When unknown foreign markup is encountered as a child of metalink:
file, metalink:metalink, Metalink Processors MAY bypass the markup
and any textual content and MUST NOT change their behavior as a
result of the markup's presence.
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When unknown foreign markup is encountered in a Text Construct,
software SHOULD ignore the markup and process any text content of
foreign elements as though the surrounding markup were not present.
6.4. Extension Elements
Metalink allows foreign markup anywhere in an Metalink document,
except where it is explicitly forbidden. Child elements of metalink:
file and metalink:metalink are considered Metadata elements and are
described below. Child elements of Person constructs are considered
to apply to the construct. The role of other foreign markup is
undefined by this specification.
6.4.1. Simple Extension Elements
A Simple Extension element MUST NOT have any attributes or child
elements. The element MAY contain character data or be empty.
Simple Extension elements are not Language-Sensitive.
simpleExtensionElement =
element * - metalink:* {
text
}
The element can be interpreted as a simple property (or name/value
pair) of the parent element that encloses it. The pair consisting of
the namespace-URI of the element and the local name of the element
can be interpreted as the name of the property. The character data
content of the element can be interpreted as the value of the
property. If the element is empty, then the property value can be
interpreted as an empty string.
6.4.2. Structured Extension Elements
The root element of a Structured Extension element MUST have at least
one attribute or child element. It MAY have attributes, it MAY
contain well-formed XML content (including character data), or it MAY
be empty. Structured Extension elements are Language-Sensitive.
structuredExtensionElement =
element * - metalink:* {
(attribute * { text }+,
(text|anyElement)*)
| (attribute * { text }*,
(text?, anyElement+, (text|anyElement)*))
}
The structure of a Structured Extension element, including the order
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of its child elements, could be significant.
This specification does not provide an interpretation of a Structured
Extension element. The syntax of the XML contained in the element
(and an interpretation of how the element relates to its containing
element) is defined by the specification of the Metalink extension.
7. IANA Considerations
A Metalink Document, when serialized as XML 1.0, can be identified
with the following media type:
MIME media type name: application
MIME subtype name: metalink+xml
Mandatory parameters: None.
Optional parameters:
"charset": This parameter has semantics identical to the charset
parameter of the "application/xml" media type as specified in
[RFC3023].
Encoding considerations: Identical to those of "application/xml" as
described in [RFC3023], Section 3.2.
Security considerations: As defined in this specification.
In addition, as this media type uses the "+xml" convention, it
shares the same security considerations as described in [RFC3023],
Section 10.
Interoperability considerations: There are no known interoperability
issues.
Published specification: This specification.
Applications that use this media type: No known applications
currently use this media type.
Additional information:
Magic number(s): As specified for "application/xml" in [RFC3023],
Section 3.2.
File extension: .metalink
Fragment identifiers: As specified for "application/xml" in
[RFC3023], Section 5.
Base URI: As specified in [RFC3023], Section 6.
Macintosh File Type code: TEXT
Person and email address to contact for further information: Anthony
Bryan <anthonybryan@gmail.com>
Intended usage: COMMON
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Author/Change controller: IESG
8. Security Considerations
Publishers are encouraged to offer Metalink documents via
authenticated HTTP under TLS as specified in [RFC2818].. Publishers
are also encouraged to include digital signatures of the files within
the Metalink Documents if they are available.
8.1. URIs
Metalink Processors handle URIs. See Section 7 of [RFC3986].
8.2. IRIs
Metalink Processors handle IRIs. See Section 8 of [RFC3987].
8.3. Spoofing
Metalink Processors should be aware of the potential for spoofing
attacks where the attacker publishes Metalinks with false
information. Malicious publishers might create Metalink Documents
containing inaccurate information anywhere in the document. At best,
this could deceive unaware downloaders that they are downloading a
malicious or worthless file. At worst, malicious publishers could
attempt a distributed denial of service attack by inserting unrelated
IRIs into Metalink Documents.
8.4. Encryption and Signing
Metalink Documents can be encrypted and signed using
[REC-xmlenc-core] and [REC-xmldsig-core], respectively, and are
subject to the security considerations implied by their use.
Digital signatures provide authentication, message integrity, and
non-repudiation with proof of origin. Encryption provides data
confidentiality.
9. References
9.1. Normative References
[BITTORRENT]
Cohen, B., "The BitTorrent Protocol Specification",
BITTORRENT 11031, February 2008,
<http://www.bittorrent.org/beps/bep_0003.html>.
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[ISO3166] International Organization for Standardization, "ISO 3166:
1988 (E/F) - Codes for the representation of names of
countries - The International Organization for
Standardization, 3rd edition, 1988-08-15.", ISO Standard
3166, 1988.
[ISO639-2]
International Organization for Standardization, "ISO 639-
2:1998 - Codes for the representation of names of
languages -- Part 2: Alpha-3 code - edition 1,
1998-11-01, 66 pages, prepared by a Joint Working Group of
ISO TC46/SC4 and ISO TC37/SC2.", ISO Standard 639-2, 1998.
[REC-xml] Yergeau, F., Paoli, J., Bray, T., Sperberg-McQueen, C.,
and E. Maler, "Extensible Markup Language (XML) 1.0
(Fourth Edition)", World Wide Web Consortium
Recommendation REC-xml-20060816, August 2006,
<http://www.w3.org/TR/2006/REC-xml-20060816>.
[REC-xml-c14n]
Boyer, J., "Canonical XML Version 1.0", W3C REC REC-xml-
c14n-20010315, March 2001,
<http://www.w3.org/TR/2001/REC-xml-c14n-20010315>.
[REC-xml-exc-c14n]
Eastlake, D., Boyer, J., and J. Reagle, "Exclusive XML
Canonicalization Version 1.0", W3C REC REC-xml-exc-c14n-
20020718, July 2002,
<http://www.w3.org/TR/2002/REC-xml-exc-c14n-20020718>.
[REC-xml-infoset]
Cowan, J. and R. Tobin, "XML Information Set (Second
Edition)", World Wide Web Consortium Recommendation REC-
xml-infoset-20040204, February 2004,
<http://www.w3.org/TR/2004/REC-xml-infoset-20040204>.
[REC-xml-names]
Hollander, D., Bray, T., Tobin, R., and A. Layman,
"Namespaces in XML 1.0 (Second Edition)", World Wide Web
Consortium Recommendation REC-xml-names-20060816,
August 2006,
<http://www.w3.org/TR/2006/REC-xml-names-20060816>.
[REC-xmlbase]
Marsh, J., "XML Base", W3C REC W3C.REC-xmlbase-20010627,
June 2001,
<http://www.w3.org/TR/2001/REC-xmlbase-20010627>.
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[REC-xmldsig-core]
Solo, D., Reagle, J., and D. Eastlake, "XML-Signature
Syntax and Processing", World Wide Web Consortium
Recommendation REC-xmldsig-core-20020212, February 2002,
<http://www.w3.org/TR/2002/REC-xmldsig-core-20020212>.
[REC-xmlenc-core]
Eastlake, D. and J. Reagle, "XML Encryption Syntax and
Processing", World Wide Web Consortium Recommendation REC-
xmlenc-core-20021210, December 2002,
<http://www.w3.org/TR/2002/REC-xmlenc-core-20021210>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
[RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media
Types", RFC 3023, January 2001.
[RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet:
Timestamps", RFC 3339, July 2002.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource
Identifiers (IRIs)", RFC 3987, January 2005.
9.2. Informative References
[ISO.8601.1988]
International Organization for Standardization, "Data
elements and interchange formats - Information interchange
- Representation of dates and times", ISO Standard 8601,
June 1988.
[RELAX-NG]
Clark, J., "RELAX NG Compact Syntax", December 2001, <http
://www.oasis-open.org/committees/relax-ng/
compact-20021121.html>.
[RFC4287] Nottingham, M. and R. Sayre, "The Atom Syndication
Format", RFC 4287, December 2005.
[W3C.NOTE-datetime-19980827]
Wolf, M. and C. Wicksteed, "Date and Time Formats", W3C
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NOTE NOTE-datetime-19980827, August 1998,
<http://www.w3.org/TR/1998/NOTE-datetime-19980827>.
[W3C.REC-xmlschema-2-20041028]
Malhotra, A. and P. Biron, "XML Schema Part 2: Datatypes
Second Edition", W3C REC REC-xmlschema-2-20041028,
October 2004,
<http://www.w3.org/TR/2004/REC-xmlschema-2-20041028>.
Appendix A. Contributors
The layout and content of this document relies heavily on work
pioneered in the Atom Syndication Format as specified in [RFC4287].
The following people contributed to preliminary versions of this
document: Paul Burkhead, Kristian Weston, Darius Liktorius, Michael
Burford, Giorgio Maone, Manuel Subredu, Tatsuhiro Tsujikawa, A. Bram
Neijt, Max Velasques, Manolo Valdes, Urs Wolfer, Frederick Cheung,
Nils Maier, Hampus Wessman, Neil McNab, Hayden Legendre, Danny Ayers,
Nick Dominguez, Rene Leonhardt, Per Oyvind Karlsen, Gary Zellerbach,
James Clark, Daniel Stenberg, Peter Poeml, Matt Domsch, Ian
Macfarlane, Dave Cridland, and Julian Reschke. The content and
concepts within are a product of the Metalink community.
The Metalink community has dozens of very active contributors who
proposed ideas and wording for this document, including:
Nicolas Alvarez, Patrick Ruckstuhl, Mike Wells, Sebastien Willemijns,
Micah Cowan, Dan Fandrich, Francis Giannaros, Yazsoft, Lukas
Appelhans, KGet developers, FDM Team, Orbit Team, Arne
Babenhauserheide, Mathias Berchtold, Xienzhenyu and TheWorld Browser
Team, Xi Software, Bridget and Ethan Fletcher, Ruben Kerkhof,
Agostino Russo, Gervase Markham, Salvatore and Robin Musumeci, Steve
and Rachel Eshelman, Lucas Hewett, Ryan and Darren Cronin, Dave
Winquist, Bob Denison, Wes Shelton, Kees Cook, Josh Colbert, Steve
Kleisath, Chad Neptune, Nick Carrabba, Chris Carrabba, Erin Solari,
Derick Cordoba, Ryan Alexander, John Sowder, Sandra Amisano, Tom
Mainville, Janie Wargo, Jason Hansen, Tim Bray, Dan Brickley, Markus
Hofmann, Dan Connolly, Tim Berners-Lee, Harry Chen, Adrien Macneil,
Louis Suarez-Potts, Ross Smith, Rahul Sundaram, Jesse Keating, Michal
Bentkowski, Andrew Pantyukhin, Judd Vinet, Charles Landemaine, Pascal
Bleser, Jeff@BLAG, Yuichiro Nakada, Jereme Hancock, Marcel Hauser,
Jeff Covey, Doug Lang, Seth Brown, Alexander Lazic, Mayank Sharma,
Robin Heggelund Hansen, Steve Langasek, Federico Parodi, Stefano
Verna, Jason Green, James Linden, Matt Nederlanden, Aren Olsen, Dag
Odenhall, Troy Sobotka, Corey Farwell, Ed Lee, Shawn Wilsher, Mike
Connor, Anand Muttagi, Debi Goulding, the Anthony Family, the Bryan
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Family, Juanita Anthony and Zimmy Bryan.
Appendix B. RELAX NG Compact Schema
This appendix is informative.
The Relax NG schema explicitly excludes elements in the Metalink
namespace that are not defined in this revision of the specification.
Requirements for Metalink Processors encountering such markup are
given in Sections 6.2 and 6.3.
# -*- rnc -*-
# RELAX NG Compact Syntax Grammar for the
# Metalink Format Specification Version 1
namespace metalink = "http://www.metalinker.org"
namespace xsd = "http://www.w3.org/2001/XMLSchema"
# Common attributes
metalinkCommonAttributes =
attribute xml:base { metalinkUri }?,
attribute xml:lang { metalinkLanguageTag }?,
undefinedAttribute*
# Text Constructs
metalinkTextConstruct =
metalinkCommonAttributes,
text
# Date Construct
metalinkDateConstruct =
metalinkCommonAttributes,
xsd:dateTime
start =
element metalink:metalink {
element metalink:generator {
attribute uri { metalinkUri }?,
attribute version { text }?,
metalinkTextConstruct
}
element metalink:origin { metalinkUri }?,
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element metalink:type { "static" | "dynamic" }?,
element metalink:published { metalinkDateConstruct }?,
element metalink:updated { metalinkDateConstruct }?,
element metalink:files {
element metalink:file {
attribute name { metalinkTextConstruct },
element metalink:identity { metalinkTextConstruct }?,
element metalink:version { metalinkTextConstruct }?,
element metalink:size { xsd:integer }?,
element metalink:description { metalinkTextConstruct }?,
element metalink:license {
attribute uri { metalinkUri }?,
attribute name { metalinkTextConstruct }?,
}?,
element metalink:logo { metalinkUri }?,
element metalink:publisher {
attribute uri { metalinkUri }?,
attribute name { metalinkTextConstruct }?,
}?,
element metalink:language { metalinkTextConstruct }?,
element metalink:copyright { metalinkTextConstruct }?,
element metalink:license { metalinkTextConstruct }?,
element metalink:os { metalinkTextConstruct }?,
element metalink:verification {
hash+,
element metalink:pieces {
attribute length { metalinkTextConstruct },
attribute type { metalinkTextConstruct },
hash+
}+,
element metalink:signature {
attribute type { "pgp" },
text
}
}?,
element metalink:resources {
element metalink:metadata {
attribute preference { xsd:integer }?,
attribute type { metalinkTextConstruct },
metalinkUri
element metalink:url {
attribute location { xsd:string {
minLength = "2" maxLength="2"}
}?,
attribute preference { xsd:integer }?,
metalinkUri
}+
}
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}+
}
}
hash =
element metalink:hash {
attribute piece { metalinkTextConstruct }?,
attribute type { metalinkTextConstruct },
text
}
# As defined in RFC 3066
metalinkLanguageTag = xsd:string {
pattern = "[A-Za-z]{1,8}(-[A-Za-z0-9]{1,8})*"
}
# Unconstrained; it's not entirely clear how IRI fit into
# xsd:anyURI so let's not try to constrain it here
metalinkUri = text
# Simple Extension
simpleExtensionElement =
element * - metalink:* {
text
}
# Structured Extension
structuredExtensionElement =
element * - metalink:* {
(attribute * { text }+,
(text|anyElement)*)
| (attribute * { text }*,
(text?, anyElement+, (text|anyElement)*))
}
# Other Extensibility
extensionElement =
simpleExtensionElement | structuredExtensionElement
undefinedAttribute =
attribute * - (xml:base | xml:lang | local:*) { text }
undefinedContent = (text|anyForeignElement)*
anyElement =
element * {
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(attribute * { text }
| text
| anyElement)*
}
anyForeignElement =
element * - metalink:* {
(attribute * { text }
| text
| anyElement)*
}
# EOF
Index
A
application/metalink+xml Media Type 25
C
copyright XML element 14
D
description XML element 14
F
file XML element 11
files XML element 10
G
generator XML element 14
Grammar
metalinkCommonAttributes 7
metalinkCopyright 14
metalinkDateConstruct 8
metalinkDescription 14
metalinkFile 11
metalinkFiles 10
metalinkGenerator 15
metalinkHash 15
metalinkIdentity 16
metalinkLanguage 16
metalinkLicense 16
metalinkLogo 17
metalinkMetalink 9
metalinkOrigin 18
metalinkOS 18
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metalinkPieces 14
metalinkPublished 18
metalinkPublisher 18
metalinkResources 12
metalinkSignature 19
metalinkSize 19
metalinkTextConstruct 7
metalinkType 20
metalinkUpdated 20
metalinkURL 17, 20
metalinkVerification 13
metalinkVersion 21
simpleExtensionElement 24
structuredExtensionElement 24
H
hash XML element 15
I
identity XML element 16
L
language XML element 16
license XML element 16
logo XML element 17
M
Media Type
application/metalink+xml 25
metadata XML element 17
metalink XML element 9
metalinkCommonAttributes grammar production 7
metalinkCopyright grammar production 14
metalinkDateConstruct grammar production 8
metalinkDescription grammar production 14
metalinkFile grammar production 11
metalinkFiles grammar production 10
metalinkGenerator grammar production 15
metalinkHash grammar production 15
metalinkIdentity grammar production 16
metalinkLanguage grammar production 16
metalinkLicense grammar production 16
metalinkLogo grammar production 17
metalinkMetalink grammar production 9
metalinkOrigin grammar production 18
metalinkOS grammar production 18
metalinkPieces grammar production 14
metalinkPublished grammar production 18
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metalinkPublisher grammar production 18
metalinkResources grammar production 12
metalinkSignature grammar production 19
metalinkSize grammar production 19
metalinkTextConstruct grammar production 7
metalinkType grammar production 20
metalinkUpdated grammar production 20
metalinkURL grammar production 17, 20
metalinkVerification grammar production 13
metalinkVersion grammar production 21
O
origin XML element 18
os XML element 18
P
pieces XML element 13
published XML element 18
publisher XML element 18
R
resources XML element 12
S
signature XML element 19
simpleExtensionElement grammar production 24
size XML element 19
structuredExtensionElement grammar production 24
T
type XML element 19
U
updated XML element 20
url XML element 20
V
verification XML element 13
version XML element 21
X
XML Elements
copyright 14
description 14
entry 11
files 10
generator 14
hash 15
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identity 16
language 16
license 16
logo 17
metadata 17
metalink 9
origin 18
os 18
pieces 13
published 18
publisher 18
resources 12
signature 19
size 19
type 19
updated 20
url 20
verification 13
version 21
Author's Address
Anthony Bryan (editor)
Metalinker Project
Email: anthonybryan@gmail.com
URI: http://www.metalinker.org
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Full Copyright Statement
Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
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rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
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