Edit comment LC-3076 for Efficient Extensible Interchange Working Group

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Comment LC-3076

Comment Shortname:

Commenter: John Schneider <john.schneider@agiledelta.com>

Message-id:

Section of the document concerned:

[Free text description]Document as a whole1. Introduction Canonical EXI Abstract 1.1 Notational Conventions and Terminology 1.2 Need of Canonical EXI 1.3 Applications 1.4 Limitations 2. Canonical EXI Stream 3. Canonical EXI Header 4. Canonical EXI Body 4.1 EXI Alignment Options and Streams 4.2 EXI Event Selection 4.2.1 Prune productions according to specific conventions 4.2.2 Prune productions for non applicable events with content values 4.2.3 Use the event with the most accurate event 4.3 EXI Stream Order 4.4 EXI Datatypes 4.4.1 Unsigned Integer 4.4.2 Enumeration 4.4.3 Decimal 4.4.4 Float 4.4.5 Date-Time 4.4.6 String and String Table 4.4.7 Restricted Character Sets 4.4.8 Datatype Representation Map A Design Decisions A.1 Relationship to XML Security A.2 No Unicode Normalization B Canonical EXI Examples B.1 EXI Event Selection Example B-1. Example productions with event codes B.2 EXI Stream Order Example B-2. Attribute and Namespace Declaration Sorting Figure C-1. Canonical EXI used in Signature B.3 EXI Floats Example B-3. Example algorithm for converting float values t... Example B-4. Canonicalized EXI Float values C Canonical EXI Applications C.1 Signature Processing Steps C.2 Exchange EXI Options (Best Practices "Work in Progress") C.2.1 Option 1 - XML Signature element C.2.2 Option 2 - Uri scheme fragment identifier C.2.3 Option 3 - EXI options within EXI stream D References
or

Refinement of the section concerned:

Status:

open proposal pending resolved_yes resolved_no resolved_partial other assigned to Nobody Bournez, Carine Brutzman, Don Cokus, Michael Fernández, Javier D. Heuer, Joerg Käbisch, Sebastian Kamiya, Takuki Kuntschke, Richard Matsukura, Ryuichi McGregor, Don Peintner, Daniel Quin, Liam Shah, Grishma ZERGAOUI, Mohamed

Type: substantive editorial typo question general comment undefined

Resolution status:

Response drafted Resolution implemented Reply sent to commenter

Response status:

No response from Commenter yet Commenter approved disposition Commenter objected to disposition
Commenter's response (URI):

Comment:

12. Section 4.4.5: This section states that EXI Date-Time values
MUST be canonicalized according to the XML Schema dateTime canonical
representation. While this definition might be convenient, it is not
entirely appropriate for canonicalization and will lead to surprising
results for some. The canonical form for XML Schema dateTime values is
defined to make it easy to determine whether two Date-Time values refer
to the same instant, regardless of the timezone used. However, for many
applications, the Date-Time timezone is an important piece of information
that should be preserved. As such, it will be surprising if the digital
signature is not able to detect changes to this information. In addition,
those using canonical EXI as a transmission format will be surprised if
the canonical EXI format loses all their timezone information and changes
all Date-Time values to GMT. Recommend this section be updated to exclude
canonicalization of timezones in Date-Time values.

Related issues: (space separated ids)

WG Notes: The discussion ultimately resurrected during review in preparation for CR. Please see: https://lists.w3.org/Archives/Public/public-exi/2016Apr/0003.html https://lists.w3.org/Archives/Public/public-exi/2016May/0005.html From this, you can see the commenter was satisfied with the resolution described below. See also: https://www.w3.org/2005/06/tracker/exi/issues/108

Resolution: Moreover, I think it is important to facilitate identifying which canonicalization variation is used. To do so I propose defining identifiers for each variation in the spirit Canonical XML does. I do see 6 possible choices: http://www.w3.org/TR/exi-c14n (default: with EXI Options, with schemaId, with dateTime normalization) http://www.w3.org/TR/exi-c14n#WithoutEXIOptions http://www.w3.org/TR/exi-c14n#WithoutSchemaId http://www.w3.org/TR/exi-c14n#WithoutDatetimeNormalization http://www.w3.org/TR/exi-c14n#WithoutEXIOptionsAndWithoutDatetimeNormalization http://www.w3.org/TR/exi-c14n#WithoutSchemaIdAndWithoutDatetimeNormalization

(Please make sure the resolution is adapted for public consumption)