p., Thanks for looking at it. I think the RFC 4234 parse of the elements in the RFC 4512 definition would be as a 'concatenation' (based on rule->elements->alternation->concatenation). To get "any order" behavior under RFC 4234, I think the elements in the definition would be separated by '/' characters, and all the elements would be enclosed in a group with a repetition element. There's an example in the "Generalized Time" definition (RFC 4517, section 3.3.13) that shows why the optional members must be in sequence by default. In that particular case, the [fraction] can't be allowed to appear before the [minute ...] part, or it would be ambiguous whether the final "3015" in "2007100807.53015" was part of the fraction or a minute and second that appears (for no good reason) after the fraction ".5"

The reason I reported it was that I wrote a parser for LDAP schema based directly on the formal grammar downloaded all the schema from OpenLDAP as a test. That was the only schema that broke, and only on the one element. I did not have any trouble with the OpenLDAP software accepting the schema. If you use a grammar builder (I used ANTLR) rather than a hand-coded parser, being permissive makes it a bit more complex. Allowing the elements to appear in any order would be easy to parse for the RFC 4512 elements, because they happen to be defined with markers ("NAME", "DESC" and so on) that makes them easy to differentiate, but then enforcing at-most-once semantics on the elements requires either an additional pass or some hand coded predicates to check for duplicates in a data structure being built on-the-fly.

-- Brian

On 10/8/07, Pierangelo Masarati ando@sys-net.it wrote:

Not sure if ordering of optional sequence members is required by RFC 4234, but the change you suggest sounds harmless. OpenLDAP software, in this sense, is usually permissive in what is accepted and strict in what is emitted.

Thanks, p.

Ing. Pierangelo Masarati OpenLDAP Core Team

SysNet s.r.l. via Dossi, 8 - 27100 Pavia - ITALIA http://www.sys-net.it

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