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Subject: RE: [wsdm] Groups - Manageable Relationships for WSDM .doc uploaded


A few more comments, between <wv></wv>.
 
Looks like we are making great progress, I am looking forward to finalizating this at the F2F (if not this week).
 
Regards,
 
William

Conceptual section:
1. Can a participant play several roles in a relationship? for example, be related to itself?
For example, if an application A is dependent on (uses) a security service S then security relationship: A uses S. But if A is depenent on a security service and also provides the security service itself, then security relationship: A uses A. The wording in the first paragraph made me wonder this... 

it is not limited by the definition of the information type. yes you can of you'd like to.  

<wv>Yes, there is no restriction preventing this.</wv> 


2. When participants are NOT WSDM manageable resources... what are they? unmanaged resources? identities of resources?  

whatever the reference tells you. The dialect tells you what kind of reference that is. Therefore it could be just a reference to a functional endpoint (WSA) or things like SCSI ID, etc. (that is if one defines such dialect)  

<wv>In our conceptual model, they are "resources". Whether or not they are managed, at this point we don't know.</wv>  

Relationship Markup:
1. I think we’re mixing relationship type definition schema and relationship instance schema.

A relationship Type contains the type name, valid roles, directionality, and cardinality. You don't have to repeat this information for every instance of a relationship.  

theoretically yes, practically it is hard to process. Locating definitions or baking-in the relationship type understanding is harder to code than just a relationship instance that basically tells you everything you need. <Type> placeholder is the one to do dereferencing to the semantics.

Without this one cannot build a "map" of the resources without understanding each relationship type. Which may not always be possible with custom extensions.  

<wv>How about simply having an optional "target=true" attribute on a role. In the case of a directional binary relationship this gives you the target and you can draw your arrows. In more complex cases, you don't use this and you're on your own to figure out how to draw the relationship.</wv>  

A relationship instance contains the type, participant (including the role and reference), and control point reference

2. Should we add the ability to define the WSDL interface a role must support in order be that role in the relationship? Or is it always the same as the role's URI. That doesn't seem quite right either. 

I don't think I intended to mimic BPEL partnerLink with a relationship. BPEL partnerLink may be one of the reference dialects. Such semantics as requiring to support particular WSDL portType to be in the relationship is part of the relationship definition and therefore overlays the markup.

<wv>Yes, if the needed portType is defined as part of the relationship then you don't need to repeat that info. In the case where there is a concrete realization of a requirement that needs to be fulfilled by participants, that would be a property of the relationship.</wv>  

 
3. Should we add a definition of the WSDL interface that a control point for this relationship would have to support? 

 That is the last section in that doc. It is TBD. I though to say things like it MUST be a WS-Resource and it MUST implement WS-RL. So yes, but this is a TODO.  

<wv>I proposed a WSRP document for this resource in my initial proposal.</wv>  

4. Is the same schema used by relationship participants (I suppose through the relationship capability) as by relationships provided by non-participants (some third party)? Are we going to address the second case? 

I guess yes (if I understand your question). The same markup is used to report relationships by participants and non-participants. The instance information would be the same. The thing is that the manageable relationships capability could be implemented by a participant or anybody else (e.g. a relationship service). This is said in the text. 

<wv>+1</wv> 

 5. Why do we need multiple references (presumably of the same participant) in the same participant????? What is the use case for this?

There is an example in the doc. I can point one to a SCSI HDD which is a Web Service, however is not WSDM manageable. So the consumer of the relationship information could locate the HDD and access it as a Web Service. That is if 1) the provider knows two reference dialects and 2) if the consumer asks for them. 


On directionality, target/source semantics may be hard to preserve in relatoinships where there are more than 2 roles/participants or are peer type relationships. So, at first glance it seems more flexible to indicate directionality in its own element.  

No! The relationship assumes directionality, individual participants are either on one or the other side of the direction. To represent many related resources with varying directionality, use many relationship instances. That is the right approach. I've added multiple participants to model things like "A and B and C are friends". (There was a more intricate use case from CIM).

<wv>Igor, if I understand what Heather is saying here, she was defending your <Direction/> element versus my suggestion that this be conveyed by using pre-defined roles for target and source. In any case, I want to make it clear that I want to allow arbitrary roles to be created. The question is whether to predefine some roles or not. I am not hell-bent on that. And earlier in this email, I proposed to use a simpler "target" attribute on a role to replace <Direction/> if we don't use predefined source/target roles.</wv> 

 
RelationshipCapability

1. Does it make sense to add some convenience operation here... 'getRelatedResources'? perhaps with a parameter of resource type to narrow the results.  

There is a WS-RF query example. This would be quite unnecessary. We can only guess what are the most common querties. Why build code around guesses?  

<wv>Isn't all of spec writing an exercize in educated guesses? Many resource-constrained resources will not support XPath-based query but still need to be able to return their relationships on a certain kind. So I think such an operation would be useful.</wv> 

2. Who sends these events? The relatoinship participant? A third party that is aware of (or caused creation of) the relationship?

Whomever implemented the manageable relationships capability. It may be the participant itself or something that observes the participants from the outside. the provider of the capability emits the events. 

 

<wv>+1. In general, whoever allows you to register for the events is responsible for making sure the events get emitted.</wv> 

 
Should there be a way to advertise relationship information about a resouce - relationships it can participate.. or must participate in. Allowable cardinality of the relationship (I can only be in one security service relationship, but I must be in one.)?  

This is too advanced for 1.0. See WS-ServiceGroup for participant rules, etc.  

<wv>Not sure this is too advanced but I agree we need to look at this in the context of our collection mechanism.</wv>  

Thanks for all your work Igor and William.

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

Inactive hide details for "Vambenepe, William N" <vbp@hp.com>"Vambenepe, William N" <vbp@hp.com>


          "Vambenepe, William N" <vbp@hp.com>

          08/06/2004 09:48 PM


To

<Igor.Sedukhin@ca.com>, <wsdm@lists.oasis-open.org>

cc


Subject

RE: [wsdm] Groups - Manageable Relationships for WSDM .doc uploaded


Thanks Igor, this is a good merge of both your proposal and mine, as
well as the discussions that took place on the phone.

A few comments (in addition to Bryan's):

- I can go with multiple references per participant as long as we make
it crystal clear that these are all references to the same resource (and
by grouping them together the producer of this relationship element
asserts that these references point to the same resource). Also, we need
to specify that if the producer of this relationship element knows of a
manageability representation for participants in the relationship it
MUST include the EPR to this manageability representation as one of the
references for this participant.

- Having roles described as URIs is fine, but the current mechanism has
people create 3 URIs in most cases for each relationship type (one for
the type and one for each role in the "common" case of directional
binary relationships). And I don't find the <Direction/> element too
elegant. How about this alternative:
MUWS pre-defines three roles (and assigns URIs to them): a "source"
role, a "target" role and a "participant" role. When people create new
relationship types, if the relationship is binary and directional (e.g.
"DependsOn") they use the MUWS-defined "source" and "target". If the
relationship is non-directional and has only one role (e.g. "Neighbor")
then they use the MUWS-defined "participant" role. In all other cases
they create their own roles (and corresponding URIs) as necessary.
As a result we can drop the <Direction/> element. If the relationship is
binary and directional (the case in which <Direction/> would be useful)
then people who define the relationship type would use the MUWS-defined
"target" and "source" role URIs so the consuming tools would know in
which direction to draw the arrow.
With this approach we can support the exceptional case where the source,
target and participant roles are not enough without making the common
case more complex than needed.

- In the description of the "manageable" reference type, we need to make
it clear that not only is the content an EPR, it is an EPR that points
to a manageability representation of the resource (in the MUWS sense of
the term).

- Finally a small thing: I assume that minOccurs for <Participant/> is 2
not 1. I know it's not easy to express this in pseudo-schema, but maybe
a more correct way to write it is:
<Participant/>
<Participant/>+
Rather then just
<Participant/>+
But it still looks a bit strange.

Regards,

William

-----Original Message-----
From: Igor.Sedukhin@ca.com [mailto:Igor.Sedukhin@ca.com]
Sent: Friday, August 06, 2004 12:29 PM
To: wsdm@lists.oasis-open.org
Subject: [wsdm] Groups - Manageable Relationships for WSDM .doc uploaded

The document revision Manageable Relationships for WSDM .doc has been
submitted by Igor Sedukhin (Igor.Sedukhin@ca.com) to the OASIS Web
Services Distributed Management TC document repository.
This document is revision #1 of Manageable Relationships for WSDM .doc.

Document Description:
Assembled taking into account the discussion that we had. This one may
make everybody happy...
1) N-ary relationships
2) optional directionality
3) many references
4) controllable relationships
5) manageable relationships

Download Document:
http://www.oasis-open.org/apps/org/workgroup/wsdm/download.php/8515/Mana
geable%20Relationships%20for%20WSDM%20.doc

View Document Details:
http://www.oasis-open.org/apps/org/workgroup/wsdm/document.php?document_
id=8515

Revision:
This document is revision #1 of Manageable Relationships for WSDM .doc.
The document details page referenced above will show the complete
revision history


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