Re: [salud] New version of the ABNF-syntax

[[e-mail] (Dale R. Worley)]

(as an individual)

OK, we can see that this is going well because the ABNF is quite
simple and clear.  I've made the following adjustments in the version
below:

- aligned the columns and normalized the spacing between elements
- put blank lines to break the rules in to sections, and reordered the rules
- applied Paul's simplification
- changed the rule "YY=CC" to "YY=DIGIT DIGIT", because YY is
    semantically different from CC
- removed DIGIT-1-9 and DIGIT-2-9, because they are not used
- added a rule for "toplabel"
- broken private-name into two parts, because one of the rules needs
  to refer to the provider-id-and-date part

      alert-URN         = "urn:alert:" alert-identifier
      alert-identifier  = alert-category ":" alert-indication
      alert-category    = alert-name
      alert-indication  = alert-name *(":" alert-name)
      alert-name        = label / private-name
      name              = label
      private-name      = label "@" provider
      provider          = provider-id ["(" date ")"]
      provider-id       = 1*(label ".") toplabel
[I'm not sure I like the names of the two preceding rules.]

      toplabel          = ALPHA [ *let-dig-hyp let-dig ]
      label             = let-dig [ *let-dig-hyp let-dig ]
      let-dig-hyp       = let-dig / "-"
      let-dig           = ALPHA / DIGIT

      date              = [CC] YY [ "-" MM ["-" DD] ]
      CC                = DIGIT DIGIT
      YY                = DIGIT DIGIT
      MM                = ( "0" %x31-39 ) / ( "1" %x30-32 )
      DD                = ( "0" %x31-39 ) / ( %x31-32 DIGIT ) / "30" / "31"
      ALPHA             = %x41-5A / %x61-7A   ; A-Z / a-z
      DIGIT             = %x30-39 ; 0-9

I want to make two modifications so that the ABNF symbols can be used
to describe the semantics more easily:

1. I want to have a symbol that refers to the component of the URN that
can be removed during the resolution algorithm.  Currently, alert-name
is used for both alert-category and as a component of
alert-indication.

2. I want to have a syntactic distinction between alert-names which have
standard meanings and alert-names which are privately defined.

However, both of these changes are messy and unclear when written in
ABNF.  So I will see if I can use semantic specifications to achieve
the same result.

The semantic rules are:

1) provider-id:  This is intended to match the allowed ABNF for domain
names.  (What is the correct normative reference?  With
internationalization, is our syntax still correct?)

2) date:  <date> syntax is a subset of ??? in RFC 3339.

2a) If <date> is absent from <private-name>, it defaults to 2013-01-01.
2b) If <DD> or <MM> are absent, each defaults to 01.
2c) If <CC> is absent, it defaults to 20.

In all situations, including comparison of URNs and determining which
entity defines the meanings of <alert-name>s, <provider>s are
interpreted as if they contain <date> values with a full "CCYY-MM-DD"
value, which is determined according to the above rules.

3) Comparison of URNs:

   Comparison is case-insensitive, considering the URNs as character
   strings (but with respect to rule (2)).

4) Removing components when interpreting URNs:
   (section 8.1 step (b))

   The <alert-name>s of the URN are removed sequentially from back to
   front, until the first <alert-name> in the <alert-indication> is
   removed, at which point the URN is discarded from consideration.

5) Definition of meaning of <label>s:

5a) A <provider> has an "owner", which is the entity that was the
    registered owner of the domain name <provider-id> on the date
    <date> (with respect to rule (2)).

5b) If an entity is the first registrant of a domain name
    <provider-id>, it owns all <provider>s with that <provider-id> and
    all <date>s preceding when it registered the domain name.

5c) The entity owning <provider> defines the meaning of a
    <private-name>, whether it is used as an <alert-category> or an
    <alert-indication>.

5d) The entity owning <provider> within a <private-name> (in either an
    <alert-category> or an <alert-indication>) defines the meaning of
    each <alert-indication> which is a <label> following that
    <private-name> and preceding the next <alert-indication> which is
    a <private-name>.

5e) Entities SHOULD use only one <provider> value for all <private-name>s
    that they define.

Dale