Internet Draft Andrey Shur
Intended status: Informational Jerry Dunietz
Creation date: August 7, 2008 Microsoft Corp
Expiration date: February 2009
The "pack" URI Scheme
<draft-shur-pack-uri-scheme-04.txt>
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Abstract
A package is a logical entity that holds a collection of parts.
Given the URI for a complete package, the "pack" URI scheme provides
for the construction and use of URIs referring to individual parts
within the package. It also provides for the use of part's URIs as
base URIs for resolving relative references between the parts in a
single package.
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1. Introduction
The material in this document is also included within the "Office
Open XML File Formats" ECMA-376 Standard (http://www.ecma-
international.org/publications/standards/Ecma-376.htm, Part 2),and
is being presented as an IETF RFC for informational purposes.
The purpose of the "pack" URI scheme is:
a. To identify a part resource within a package that conforms to
Open Packaging Conventions [4].
b. To enable the use of a part's URI as a base URI for resolving
relative references to parts within the same package as it is
defined in RFC 3986, section 5.2 [1].
2. Terminology
The following terms are used as they are defined in RFC 3986 [1]:
"URI", "relative reference", "base URI", "scheme", "component",
"query", "unreserved", "sub-delims", "pct-encoded", "resource"
Section 3.3 of this document defines the terms "authority", "path",
and "segment" in a manner that is consistent with, but more
restrictive than, RFC 3986 [1].
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 RFC 2119 [3].
3. Syntax Rules
3.1. General Syntax
The "pack" URI takes the form:
"pack://" authority ["/" | path ]
The authority component contains an encoded URI that identifies
the package resource.
The path component identifies a particular part within the
package identified by the authority component. When provided, the
path component describes a path to a part in the package.
When the path component is missing, the "pack" URI identifies the
package resource as a whole.
3.2. Examples
pack://http:,,www.mysite.com,my.package/a/b/foo.xml
pack://http:,,www.mysite.com,my.package
pack://http:,,www.mysite.com,my.package/
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3.3. Grammar
The ABNF [2] (certain values are included by reference from RFC
3986 [1]):
pack-uri = "pack://" authority ["/" | path ]
authority = *( unreserved | sub-delims | pct-encoded | ":" )
path = 1*( "/" segment )
segment = 1*( pchar )
unreserved = // as specified in RFC 3986
sub-delims = // as specified in RFC 3986
pct-encoded = // as specified in RFC 3986
pchar = // as specified in RFC 3986
The <segment> grammar must fit the following restrictions:
a. A segment MUST NOT contain pct-encoded "/" or "\" characters.
b. A segment MUST NOT contain pct-encoded unreserved characters.
c. A segment MUST NOT end with a dot (".") character.
d. A segment MUST include at least one non-dot character.
4. Resolving
This section defines the process of resolving a "pack" URI to a
resource (either a package or a package part):
a. Parse the "pack" URI into the scheme, authority, and path
components, following the rules established for these
components for generic URI syntax in RFC 3986 [1].
b. In the authority component replace all "," characters with
"/".
c. In the resulting authority component un-escape all pct-encoded
ASCII characters.
d. The resulting authority component MUST hold an absolute URI
identifying the package resource.
e. If the path component is missing, "pack" URI resolves to the
package resource identified by the authority component.
f. If path component is present, "pack" URI resolves to the
part, with the name equal to the path component, within the
package identified by the authority component.
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5. Equivalence
Pack URIs are equivalent if all three of the following conditions
hold:
a. The scheme components are octet-by-octet identical after they
are converted to lowercase.
b. The decoded (as it is defined by 4.b, 4.c in this document)
authority components are equivalent URIs (the equivalency rules
by scheme, as per RFC 3986).
c. The path components are equivalent when compared as case-
insensitive ASCII strings.
6. Security Considerations
a. The "pack" URI scheme is not associated with any particular
network protocols. Its grammar is fully compatible with the
generic URI syntax defined in RFC 3986 [1]. The "pack" URI
scheme does not introduce any specific security issues related
to URI parsing and relative reference resolution.
b. Because the authority component of a "pack" URI identifies a
package, resolving a relative reference that does not begin with
"//" against a base "pack" URI will never yield a target URI
identifying a resource outside of the package.
7. IANA Considerations
The IANA registry for URI schemes
<http://www.iana.org/assignments/uri-schemes.html> SHOULD be
updated to include an entry for the "pack" URI scheme
(under Provisional URI Schemes) when the "pack" URI scheme is
accepted for publication as an RFC. This entry SHOULD contain
the following values:
Scheme Name: pack
Description: "pack" URI scheme provides for the construction and
use of URIs referring to individual parts within the package.
Reference: RFC TBD
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8. Normative References
[1] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986,
January 2005.
[2] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 4234, October 2005.
[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[4] Open Packaging Conventions. (Standard ECMA-376 "Office Open XML
File Formats", Part 2, December 2006)
9. Author's Addresses
Andrey Shur
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052-6399
Email: andreysh@microsoft.com
Jerry Dunietz
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052-6399
Email: jerryd@microsoft.com
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