Re: [XCON] apps-team review of draft-ietf-xcon-ccmp-13
Robert Sparks <rjsparks@nostrum.com> Tue, 17 May 2011 14:16 UTC
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From: Robert Sparks <rjsparks@nostrum.com>
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Cc: Henning Schulzrinne <hgs+xcon@cs.columbia.edu>, Alan Johnston <alan.b.johnston@gmail.com>, apps-discuss@ietf.org, xcon@ietf.org, Richard Barnes <barnes@bbn.com>, "iesg@ietf.org IESG" <iesg@ietf.org>
Subject: Re: [XCON] apps-team review of draft-ietf-xcon-ccmp-13
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Adding the XCON WG list On May 16, 2011, at 4:04 AM, Henry S. Thompson wrote: > I have been selected as the Applications Area Review Team reviewer for > this draft (for background on apps-review, please see > http://www.apps.ietf.org/content/applications-area-review-team). > > Please resolve these comments along with any other Last Call comments > you may receive. Please wait for direction from your document shepherd > or AD before posting a new version of the draft. > > Document: draft-ietf-xcon-ccmp-13 > > Title: Centralized Conferencing Manipulation Protocol > > Reviewer: Henry S. Thompson > > Review Date: 2011-05-13 > > Summary: This draft is almost ready for publication as a Proposed > Standard but has a few issues that should be fixed before publication > > Major Issues: > > 4.2 Data Management > > 1) The approach to detecting competing updates and their consequences > specified here seems unnecessarily complex. Was the alternative of > including version numbers in _update_ messages (so that the server > could reject any update whose target version had been superseded) > considered and rejected? If so, perhaps a brief explanation of why > it was rejected might be helful at this point. > > 2) In a related point, the statement at the end of this section that > "a client subscribed to . . . notifications . . . will always have > the most up-to-date version" is clearly false, in-so-far as it > implies that such a client is guaranteed success for any update, as > there is clearly a race condition here. > > 4.3 Data Model Compliance > > 1) Again this approach seems unnecessarily complex -- why does the > data model have to constrain the initiation of a conference in this > way. why not simply have messages which request new conference or > new user IDs? > > 2) I'm also confused by the fact that _elements_ described here as > "mandatory" are not required by the schema. Specifically in 5.1 we > will see that the 'confUserID' and 'confObjID' elements, which > correspond precisely to XCON-USERID and XCON-URI which are > described here as mandatory, appear in message type definitions as > minOccurs="0", i.e. as optional. If they are optional, why is the > above gensym complexity needed? If they are not optional, why > doesn't the schema say so? > > 3) It is unusual to refer to aspects of a data model with words such > as 'element' and 'attribute', which are better reserved for use > with respect to _XML serializations_ of data model instances. Ah, > I see by looking at draft-ietf-xcon-common-data-model that the XCON > data model is defined as an XML document. It's undoubtedly too > late to do anything about that, but confounding data models and XML > serializations is usually considered to be a mistake. . . > > 11. XML Schema > > An http URI should be provided where this schema document can be found > on its own, and an update policy for it (or, preferably, _two_ URIs, > one for exactly this schema document, and one which will be updated if > this document is revised or superseded). (Likewise for DataModel.xsd > and rfc4575.xsd.) > > 12.5 CCMP Protocol Registry > > Why are these registries needed? No role is specified for them > anywhere in the body of the document. Registries are not free, and if > all the information in the registry is also in the published schemas > it's not at all clear what purpose they will serve. > > Minor Issues: > > 6.2. Alice gets detailed information about a specific blueprint > > The blueprintResponse message is not schema-valid per ccmp.xsd. On > lines 32 and 33 of the example read > <xcon:floor-request-handling>confirm > </xcon:floor-request-handling> > The problem really lies in DataModel.xsd -- whereas (correctly) > ccmp.xsd uses xs:token as the base type for enumerated types, > DataModel.xsd (in draft-ietf-xcon-common-data-model) uses xs:string, > and the string value of the above element is "confirm > ", which is not one of the allowed values. The > example should be corrected, or, for preference, the schema in > draft-ietf-xcon-common-data-model should be changed to use xs:token as > the base type for join-handling-type and all other enumerated types. > > A similar problem occurs in the response in 6.3 > (floor-request-handling) > > 6.9 Alice exploits a CCMP server extension > > For compatibility with the actual response given, the extension schema > document should have a target namespace, as follows: > > <?xml version="1.0" encoding="UTF-8"?> > <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" > targetNamespace="http://example.com/ccmp-extension-schema.xsd" > xmlns="http://example.com/ccmp-extension-schema.xsd"> > > <xs:element name="confSummary" type="conf-summary-type"/> > > <xs:complexType name="conf-summary-type"> > <xs:sequence> > <xs:element name="title" type="xs:string"/> > <xs:element name="status" type="xs:string"/> > <xs:element name="public" type="xs:boolean"/> > <xs:element name="media" type="xs:string"/> > </xs:sequence> > </xs:complexType> > > </xs:schema> > > Or, better, the example _and_ the schema should be changed to read as > follows: > > <?xml version="1.0" encoding="UTF-8" standalone="yes"?> > <ccmp:ccmpResponse xmlns:info="urn:ietf:params:xml:ns:conference-info" > xmlns:ccmp="urn:ietf:params:xml:ns:xcon:ccmp" > xmlns:xcon="urn:ietf:params:xml:ns:xcon-conference-info" > xmlns:example="http://example.com/ccmp-extension"> > <ccmpResponse xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" > xsi:type="ccmp:ccmp-extended-response-message-type"> > <confUserID>xcon-userid:Alice@example.com</confUserID> > <confObjID>xcon:8977794@example.com</confObjID> > <operation>retrieve</operation> > > > <response-code>200</response-code> > <response-string>success</response-string> > <ccmp:extendedResponse> > <extensionName>confSummaryRequest</extensionName> > <example:confSummary> > <title> Alice's conference </title> > <status> active </status> > <public> true </public> > <media> audio </media> > </example:confSummary> > </ccmp:extendedResponse> > </ccmpResponse> > </ccmp:ccmpResponse> > > <?xml version="1.0" encoding="UTF-8"?> > <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" > targetNamespace="http://example.com/ccmp-extension" > xmlns="http://example.com/ccmp-extension"> > > <xs:element name="confSummary" type="conf-summary-type"/> > > <xs:complexType name="conf-summary-type"> > <xs:sequence> > <xs:element name="title" type="xs:string"/> > <xs:element name="status" type="xs:string"/> > <xs:element name="public" type="xs:boolean"/> > <xs:element name="media" type="xs:string"/> > </xs:sequence> > </xs:complexType> > > </xs:schema> > > Otherwise I've checked all the schemas for conformance and the > examples for schema-validity. > > 12.2 XML Schema Registration > > Should include pointers to the RFCs which include the text of the > schema documents named as "DataModel.xsd" and "rfc4575.xsd" in the > schema docuemnt given in section 11. > > 12.3 Media Type Registration > > It seems unlikely that the proposed extension of 'ccmpxml' will see > much use---4 characters seems to be the practical limit for > extensions. > > Nits: One more proofreading pass over the first three sections would > be a good idea. . . > > ht > -- > Henry S. Thompson, School of Informatics, University of Edinburgh > 10 Crichton Street, Edinburgh EH8 9AB, SCOTLAND -- (44) 131 650-4440 > Fax: (44) 131 651-1426, e-mail: ht@inf.ed.ac.uk > URL: http://www.ltg.ed.ac.uk/~ht/ > [mail from me _always_ has a .sig like this -- mail without it is forged spam]
- Re: [XCON] apps-team review of draft-ietf-xcon-cc… Robert Sparks
- Re: [XCON] apps-team review of draft-ietf-xcon-cc… Mary Barnes
- Re: [XCON] apps-team review of draft-ietf-xcon-cc… Mary Barnes