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Subject: RE: [wsdm] Events metadata; Object now or comment after its in MUWS
- From: "Sedukhin, Igor S" <Igor.Sedukhin@ca.com>
- To: "Vambenepe, William N" <vbp@hp.com>,"Heather Kreger" <kreger@us.ibm.com>,<wsdm@lists.oasis-open.org>
- Date: Fri, 19 Nov 2004 12:31:27 -0500
Again, why do we need these <event> metadata
elements? Why is topic definition with MessagePattern not good
enough?
There will be three places where for a given event there is
indication which situation category it will be of: text in the spec, topic w/
messaage pattern and this <event> element which we invent here.
Why?
<wst:topic name="MyEvent"
messageType="muws-xs:ManagementEvent">
<wst:MessagePattern Dialect="...XPath 1.0...">
//muws-xs:ManagementEvent[muws-xs:Situation/muws-xs:Category//muws-xs:ReportSituation and my:Event]
</wst:MessagePattrn>
</wst:topic>
So, in
order to simplify WSDM specification I suggest that we go with message pattern
and not invent an alternative since we've already decided on use of message
patterns and topics
It
seems that MUWS is getting a tremendous amount of changes at the 11th hour
and some have been invented in the last minute due to some incoherency with the
dependent standards e.g. WS-Topics. I suggest that we keep new inventions to the
minumum until we release 1.0.
-- Igor
Sedukhin
..
(igor.sedukhin@ca.com)
-- (631)
342-4325
..
1 CA Plaza, Islandia, NY 11749
Heather,
I am trying to picture a metadata document with a bunch of
these <event> elements in it. How do I tell what event each of these
elements relate to? Which begs the larger question: what is an
event.
In our spec, whenever we define an event we do so by
selecting a topic and a GED to represent the content of this event. So it seems
to me that our definition of an event is something uniquely identified by a URI
(topic), a GED (content) and a description of the semantics in human-readable
(at least geek-readable) form.
Based on this, I think
the event metadata element you propose would look better like
this:
<event topic="any URI" content="xs:QName">
<situationCategory>
ws-muws:category</situationCategory> ?
<severity>xs:short<severity> ?
{any} *
</event>
With @topic and @content being required so I know what
event this metadata is about.
Also, if we go with this proposal can you show us what
the topic document would look like? Like would be in topic/@messageType?
William
I had an outstanding action
item to look into using topics and message patterns to convey information that
managers would need to know about expected events ahead of time. Here are
our conclusions:
While it is
possible to advertise the values of this information in messagePattern of a
topic, the XPath would be very complicated and Igor's complaints about the
amount of processing and reverse engineering to infer the category and severity
would be valid. We are really trying to advertise information ABOUT the
event, not a broad shape or signature of the message. Instead it seems much
cleaner to advertise with the resource, who is already advertising events to be
issued, some of the important values to be expected by the manager in the
event. This enables managers to find all events that will be emitted in a
particular situationCategry or severity. It also makes it very clear what
additional elements are being added into the WEF's open content. I think
this ties to the topics work today very neatly without makeing very complex
messagePatterns.
Therefore,
I'd like to propose the following metadata for events emitted from manageable
resources:
Events are emitted
from manageable resources in the form of WSDM Event Format [WSDMEventFormat].
The event metadata element describes the types of events that can be
emitted and hints on how the WSDM Event Format will be constructed.
The form of the event
element is extended as shown here.
<xs:element name=’event’>
<xs:complexType>
<xs:sequence>
<xs:element name=’situationCategory’
type=’ws-muws:category’
minOccurs=’0’/>
<xs:element name=’severity’ type=’xs:short’
minOccurs=’0’/>
<xs:element name=’messagePattern’
type=’xs:QName’
minOccurs=’0’/>
<xs:any
namespace=’##other’
minOccurs=’0’
maxOccurs=’unbounded’/>
</xs:sequence>
</xs:complexType>
</xs:element>
<event>
<situationCategory>
ws-muws:category</situationCategory> ?
<severity>xs:short<severity> ?
<messagePattern>xs:QName</messagePattern> ?
{any} *
</event>
/mrp:event/situationCategory
The value that will appear in the
situationCategory element of the situation element of WSDM Event Format
events of this type, with potential values as defined in [WSDMBaseEvent].
/mrp:event/severity
The
value that will appear in the severity element of the WSDM Event Format events
of this type, with potential values as defined in [WSDMBaseEvent].
/mrp:event/messagePattern
The value that will be the QName of the
schema element expected in the open content model for the WSDM base event. This
value will also appear in the messagePattern for the Topic for the event.
This is an open content model, so
additional, domain specific, relevant information in the events could be
advertised.
Given the timeframe,
I propose that if there are not
objections on Friday by COB EST, that this be added to MUWS. Of course, you can
still comment during the comment period.
Heather Kreger
STSM, Web Services Lead Architect for SWG Emerging
Technologies
Author of "Java and JMX: Building Manageable
Systems"
kreger@us.ibm.com
919-543-3211 (t/l 441)
cell:919-496-9572
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