ietf-openproxy
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Re: PSRL: A Rule Specification Language for Proxy Services

2000-11-29 02:02:34

--- Andre Beck <abeck(_at_)bell-labs(_dot_)com> wrote: > 
We
thought that all existing
transaction properties (both request and response)
could be matched at
any of the four processing points. So you could
write a rule that gets
processed at processing point 4 and matches request
properties as well
as response properties. Instead of writing two
separate rules with two
different processing points you could combine them
into one rule. The
property values, however, may be modified by other
rules at earlier
processing point. All rules are matched against the
current property
value. We thought about introducing a attribute that
allows for a
comparision against the original property value, but
decided that in
almost all cases it makes more sense to work with
the current (and
possibly modified) property value.

-Andre


 Consider this case: based on some property values,
some rules are matching, say the first of such rules
is triggered. Now suppose the proxylet associated with
the triggered rule changes some of the property
values, which now match some other rules, so they may
be triggered. And this may go on. To check which new
rules are triggered the message (body and header) may
have to be parsed again.Isn't there a chance of cyclic
rule triggerring? Means after a series of rule
triggering and property value modification, the first
rule may be triggered again.
        If there is some content modification (modification
in the message body itself), then in that case, the
complete message body has to be parsed again, to find
out what new rules can match based on the current
property values. Is this feasible?
        The original EPSF Internet Draft
(draft-tomlinson-epsfw-00.txt), it says that the
message parser SHOULD parse a message in a single
parse.(Page 14). 
        So, should we allow multiple passes of message
parsing or is there any other way to do it in a single
parse?
        A suggestion is that to have a field( or element)
"Could Modify" in the rule which will tell which
property values it MAY change. This may atleast tell
which rules are mutually exclusive and won't need
separate parsing of the message for those rules
atleast.
        Does anybody have any suggestion for preventing
cycles in rule triggering? 
        Comments awaited.
Thanks
Shuvendu..

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