Integration of BIDI into the protocol

Harald Alvestrand harald at
Mon Aug 17 13:14:46 CEST 2009

James Mitchell wrote:
> John, Harald,
> A few observations on the integration of BIDI into the protocol document.
> In the draft-ietf-idnabis-protocol-14 document Section
> If the proposed label contains any characters that are written from 
> right to left it MUST meet the "bidi" criteria [IDNA2008-BIDI].
> The above implies that the label must meet the BIDI criteria, however 
> BIDI criteria is applied to a BIDI domain name. From 
> draft-ietf-idnabis-bidi-04, “The following test has been developed for 
> labels in BIDI domain names” and “A "Bidi domain name" is a domain 
> name that contains at least one RTL label”. I hesitate to provide 
> alternative text for until the following question has been answered._
> The protocol states that the proposed label contains any characters 
> written from right to left it MUST meet the bidi criteria. It does not 
> impose such requirements on labels containing no right to left 
> characters. Consider the registration of label ‘123abc’ in a zone 
> containing labels written right to left. The label does not contain 
> any right to left characters, therefore does not have to meet the BIDI 
> criteria. However this name is a BIDI domain name, yet such a name 
> would fail as the first label (LTR) does not begin with BIDI property 
> L. Is the label intended to be valid for registration given a right to 
> left zone?
In your specific case, registering "123abc" in the RTL zone "ABC" (usual 
convention applies) will lead to a domain name (network order: 
123abc.ABC) that, on its own, will display as "123abc.CBA" in an RTL 
context, but if prepended by "DEF:", forming the network order string 
DEF:123abc.ABC, will display as "CBA.abc123:FED" - which may be 
surprising to some. (I'm only 90% confident on this - people more used 
to bidi in practice may be more confident).

The WG has rejected inter-label tests, therefore all tests defined by 
the protocol as normative (MUST or SHOULD) apply only to one label at a 

Given the WG decision, I tried to make the BIDI document quite clear 
that certain properties can only be guaranteed for domain names where 
all the labels meet the test, but this is a case where people have to 
read the warnings and do something reasonable, rather than having the 
rules define that being unreasonable is forbidden.

"Warning: Contains hot liquids".
> I note also the inconsistent use of the term BIDI. In 
> draft-ietf-idnabis-protocol-14 section it is quoted and in 
> lower-case, whereas the draft-ietf-idnabis-bidi-04 uses the upper-case 
> version extensively. Also, within draft-ietf-idnabis-bidi-04 the term 
> "Bidi domain name" in Section 1.4 is inconsistent with “BIDI domain 
> names” in Section 2, and the tem “Bidi rule” in Section 10 is 
> inconsistent with the several other occurrences in the document.

Thanks, I tried to normalize it to uppercase in an earlier round, but 
didn't remain consistent in later edits. Will fix!


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