Hi Doug-
Message 00017 on the email list has the PPT slides that describe
the original problem. I think the first half of your statement is
accurate: the core problem is the number of individual event messages that the
device has to generate. One of the biggest difficulties here is in the
delays caused when event sinks are non-responsive; the slides outline
additional problems like CPU, memory, and threading overhead.
The part about lack of granularity is more nuanced, because
WS-Eventing says nothing about how events should be filtered, and leaves this
entirely to the application building on top. As a convenience, DPWS
provides a tool to do this (the Action filter—it’s provided because
it’s generically useful and lightweight) but does not lock the
application-layer spec into using it. My document highlights some ways
that an application-layer spec can provide enough granularity for devices to
send only necessary events. In some cases, the Action filter is
sufficient—in others, more application-specific filtering may be
required.
Thanks
--D
From: Doug Davis
[mailto:dug@us.ibm.com]
Sent: Thursday, December 25, 2008 8:16 PM
To: Dan Driscoll; Ohtake, Shin
Cc: ws-dd@lists.oasis-open.org
Subject: Re: [ws-dd] DPWS and Eventing (Issues 052 and 056)
Dan, Shin,
In
looking at these proposals, am I correct in assuming that the base problem is the
volume of events being generated and the lack of a way for a subscriber to
indicate which level of granularity they want? For example... one
subscriber may want all "printer events", but another may want just
"printer job status" events, while yet another may want just
"printer job status events for job id# 123" ? And doing this
filtering over the soap body is expensive (ie. xpath) and potentially hard to
manage because the event data could vary even if the type of event remains the
same?
thanks
-Doug
______________________________________________________
STSM | Web Services Architect | IBM Software Group
(919) 254-6905 | IBM T/L 444-6905 | dug@us.ibm.com
Hello all-
I took an AI
to assemble some solutions to the problem of the Action filter being insufficient
for some applications of DPWS and WS-Eventing. This set of solutions
incorporates the suggestions from Ohtake-san, and a suggestion from Elmar Zeeb.
The goal of this
document is to illustrate the different ways WSDL authors can make use of the
tools in WS-Eventing.
Several of
these suggestions are similar, but there are at least six different ways that
spec authors can work around the limitations in the Action filter.
Thanks
--D[attachment
"DPWS Eventing.docx" deleted by Doug Davis/Raleigh/IBM] ---------------------------------------------------------------------
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