SIMPLE J. Rosenberg
Internet-Draft dynamicsoft
Expires: August 9, 2004 February 9, 2004
An Extensible Markup Language (XML) Representation for Expressing
Policy Capabilities
draft-rosenberg-simple-common-policy-caps-00
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Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract
An important component of presence and location services is policy.
Policy systems allow the presentity or location target to grant
access to specific pieces of information to specific watchers or
requestors. These policy systems can be extremely simple, allowing a
user to accept or block requests based solely on the identity of the
requestor, to extremely complex, allowing for time based rules that
grant or deny specific pieces of information. Policy systems often
support vendor proprietary features. To allow for interoperability
between clients which set such policies, and servers which execute
them, it is necessary for clients to be able to determine the
capabilities of the server to which it is connected. This
specification defines an Extensible Markup Language (XML) based
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format for expressing such capabilities.
Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Overview of Operation . . . . . . . . . . . . . . . . . . . . 3
4. Structure of Policy Capabilities . . . . . . . . . . . . . . . 4
5. XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . . 4
6. Example Document . . . . . . . . . . . . . . . . . . . . . . . 5
7. Usage with XCAP . . . . . . . . . . . . . . . . . . . . . . . 6
7.1 Application Unique ID . . . . . . . . . . . . . . . . . . . . 6
7.2 Structure of Supported Permissions . . . . . . . . . . . . . . 6
7.3 Naming Conventions . . . . . . . . . . . . . . . . . . . . . . 6
7.4 Authorization Policies . . . . . . . . . . . . . . . . . . . . 7
8. Security Considerations . . . . . . . . . . . . . . . . . . . 7
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
9.1 XCAP Application Usage ID . . . . . . . . . . . . . . . . . . 7
9.2 URN Sub-Namespace Registrations . . . . . . . . . . . . . . . 8
9.3 XML Schema Registration . . . . . . . . . . . . . . . . . . . 8
Normative References . . . . . . . . . . . . . . . . . . . . . 8
Informative References . . . . . . . . . . . . . . . . . . . . 9
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 9
Intellectual Property and Copyright Statements . . . . . . . . 10
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1. Terminology
In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" are to be interpreted as described in RFC 2119 [1] and
indicate requirement levels for compliant implementations.
2. Introduction
An important component of presence [7] and location services [9] is
policy. Policy systems allow the presentity or location target
(referred to generically as the Presentity Target (PT)) to grant
access to specific pieces of information to specific watchers or
requestors (referred to as a WR). These policy systems can be
extremely simple, allowing a PT to accept or block requests based
solely on the identity of the WR, to extremely complex, allowing for
time based rules that grant or deny specific pieces of information.
[8] specifies a generic format for representing these policies, using
the Extensible Markup Language (XML). These policies consist of
conditions, actions, and transformations. That specification defines
very few actual conditions, actions or transformations. Rather, it
leaves such definitions to actual policy systems, such as [10] for
location services, and [11] for presence services.
In addition to the conditions, actions and transformations specificed
in the documents referenced above, policy systems often support
vendor proprietary features. It is also anticipated that future
specifications will be continually developed that add new types of
policies. This presents an interoperability challenge. Clients may
support policies that are not supported by the servers they are
using. This could lead to protocol failures or poor user experiences.
To address this problem, it is necessary for a capability declaration
system to be put in place. This specification defines a general
purpose format for representing policy capabilities within the
framework established in [8].
3. Overview of Operation
This specification defines an XML-based document format that allows a
server to represent its capabilities. When a client, acting as an
agent of a PT, starts up, it obtains this document from its policy
server. This specification does not prescribe a singular means of
transporting such a document between the server and the client. It is
anticipated that different systems may use different techniques.
However, for systems that make use of the XML Configuration Access
Protocol (XCAP) [4], Section 7 defines an application usage that
allows for the transfer of the document using XCAP.
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Once the document has been obtained by the client, it can determine
which actions, conditions and transformations are understood by the
server. This set is matched against those supported by the client.
Those actions, conditions and transformations supported by the
client, but not by the server, can be "greyed out" from a user
interface, for example.
It is anticipated that the capabilities of the server can change over
time. As a result, it is RECOMMENDED that clients obtain a fresh copy
of the capabilities document each time they start.
4. Structure of Policy Capabilities
A supported permission documentis an XML [5] document that MUST be
well-formed and SHOULD be valid. Supported permission documents MUST
be based on XML 1.0 and MUST be encoded using UTF-8. This
specification makes use of XML namespaces for identifying supported
permission documents and document fragments. The namespace URI for
elements defined for this purpose is a URN [2], using the namespace
identifier 'ietf' defined by [3] and extended by [6]. This URN is:
urn:ietf:params:xml:ns:supported-permissions
A supported permission document is structured much like a policy
document [8]. The root element is "supported-permissions". This
element has three children - "conditions", "actions", and
"transformations". Each of these contain a list of the supported
conditions, actions, and transformations, respectively. Generally
speaking, each specific condition, action or transformation element
(referred to as a capability element) is empty, unless it requires
additional content to further refine the capability.
This specification defines four capability elements - "identity",
"validity", "sphere" and "confirmation", matching the four
permissions defined in [8]. Other specifications that define
additional permissions SHOULD also define matching capability
elements.
A server constructing a document to represent its capabilities MUST
include all of those supported, even if those capabilities represent
mandatory-to-implement features. However, the server MAY indicate
differing sets of capabilities to different users. As such, the set
of capabilities combines both the ability and the willingness to
support those permissions.
5. XML Schema
See RFCXXXX.
END 9.3 XML Schema Registration This section registers an XML schema as per the procedures in [6]. URI: please assign. Registrant Contact: IETF, SIMPLE working group, (simple@ietf.org), Jonathan Rosenberg (jdrosen@jdrosen.net). The XML for this schema can be found as the sole content of Section 5. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] Moats, R., "URN Syntax", RFC 2141, May 1997. [3] Moats, R., "A URN Namespace for IETF Documents", RFC 2648, August 1999. Rosenberg Expires August 9, 2004 [Page 8] Internet-Draft Common Policy Capabilities February 2004 [4] Rosenberg, J., "The Extensible Markup Language (XML) Configuration Access Protocol (XCAP)", draft-ietf-simple-xcap-01 (work in progress), October 2003. [5] Bray, T., Paoli, J., Sperberg-McQueen, C. and E. Maler, "Extensible Markup Language (XML) 1.0 (Second Edition)", W3C FirstEdition REC-xml-20001006, October 2000. [6] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, January 2004. Informative References [7] Day, M., Rosenberg, J. and H. Sugano, "A Model for Presence and Instant Messaging", RFC 2778, February 2000. [8] Schulzrinne, H., Morris, J., Tschofenig, H., Cuellar, J., Polk, J. and J. Rosenberg, "Common Policy", draft-ietf-geopriv-common-policy-00 (work in progress), February 2004. [9] Cuellar, J., Morris, J. and D. Mulligan, "Geopriv requirements", draft-ietf-geopriv-reqs-04 (work in progress), October 2003. [10] Schulzrinne, H., Morris, J., Tschofenig, H., Cuellar, J. and J. Polk, "Geopriv Authorization Rules", draft-ietf-geopriv-rules-00 (work in progress), February 2004. [11] Rosenberg, J., "Presence Authorization Rules", draft-rosenberg-simple-rules-00 (work in progress), February 2004. Author's Address Jonathan Rosenberg dynamicsoft 600 Lanidex Plaza Parsippany, NJ 07054 US Phone: +1 973 952-5000 EMail: jdrosen@dynamicsoft.com URI: http://www.jdrosen.net Rosenberg Expires August 9, 2004 [Page 9] Internet-Draft Common Policy Capabilities February 2004 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any intellectual property 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; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. Copies of claims of rights made available for publication 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 implementors or users of this specification can be obtained from the IETF Secretariat. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights which may cover technology that may be required to practice this standard. Please address the information to the IETF Executive Director. Full Copyright Statement Copyright (C) The Internet Society (2004). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assignees. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION Rosenberg Expires August 9, 2004 [Page 10] Internet-Draft Common Policy Capabilities February 2004 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Rosenberg Expires August 9, 2004 [Page 11]