XPAT documentation

[Julien ÉLIE]

XPAT should probably be documented in an Informational Internet-Draft.

Maybe PAT could be specified (?)
Suggestions:

• The legacy syntax is kept: PAT header range|message-ID pattern [pattern ...]

• New metadata :body to specify that PAT will search in bodies. It would be advertised as PAT BODY in CAPABILITIES.

• Maybe another metadata :text to search in the whole article (headers+body)? It would be advertised as PAT TEXT in CAPABILITIES.

• Support for existing :bytes and :lines metadata, like what is currently implemented in INN 2.5 (for XPAT):

XPAT :lines 112- *
221 Header or metadata information for :lines follows (from overview)
112 7
113 8
.
XPAT lines 112- *
221 Header information for lines follows (from articles)
112 A bad Lines: header which is not a number!
113 1789
.

Available references:

​http://www.eyrie.org/~eagle/nntp/drafts/draft-ballou-nntpsrch-03.txt

[Julien ÉLIE]

According to Russ Allbery in an ​IETF-NNTP posting:

There are two main reasons why we didn't standardize PAT. The first and most serious is whitespace handling in patterns. Given the way that NNTP command parsing works, how would you search for a pattern containing two spaces? And what do the spaces between patterns really mean?

The second, as you mention below, is the encoding problem, which is very hairy and difficult to deal with.

IMAP has addressed the search problem at some length, and my impression was that it wasn't at all simple to deal with. I'm afraid that doing a good job of it is going to require quite a lot of work.

It would be worthwhile writing up an informational (?) I-D explaining what INN actually does with XPAT without trying to change anything about how it currently works and specifying an extension name of XPAT rather than a standardized one.