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Subject: Patterns
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One more thing regarding patterns, we
should probably state that the local part should first be canonicalized
according to the rules in the syntax specs, i.e. by removing extra /./ and
/../, and removing unnecessary percent encoding. wil. From: 1. xrd:XRD/xrd:Service/xrd:Pattern – what flavor of
regular expression should the value be (perl-compatible, posix, etc.)? Is the
full power of regexp really required, why not just simple string comparison or
prefix matching? ### Great question. Dave was the original
proposer of this feature – I'll let him answer (others, please chime in
on this.) I know you're working on very high-volume HTTP proxy resolvers
– what's your view of the best tradeoff between comparison functionality
and performance? ### [Wil] I have 3 points of concern: a) Performance-wise, because the number of regular
expressions to compile equals the number of Pattern tags (as opposed to a
single pattern matched against multiple candidates), it may be expensive for
proxy resolvers. However, I don’t have concrete statistics to prove
my point. b) If a regexp is valid but contains a logic error, there is
no way for the registry to verify. c) Standard – which flavor of regular expression to
use? Various regular expression libraries support different options. If we
support regular expressions, users might ask: how to specify case insensitive
match? How to do negation? Are Unicode character properties (\p & \P)
supported? |
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