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Subject: RE: [asap] questions/concerns on initial working draft doc (and scope)


Title: RE: [asap] questions/concerns on initial working draft doc (and scope)
Keith,
I enumerated your paragraphs in order to separate my answers:
 
Re #1: It's not about terminology. I am concerned about monitoring and state/properties update support being principal requirements for ASAP compliance, as it requires stateful implementations.
 
Re #2: Agree. I re-read your definition and "method" should be renamed to "operation".
 
Re #3: Yes, I do. That's the reason I joined this TC :-)
IMHO, there's a need for standard protocol
- defines how the originatorURI (compliant with WS-Addressing) is going to be passed to the async WS,
- defines correlator ID and its use (misc. issues incl. ID format, passing as a part of the header vs. as a part of the message, correlation scope, etc.)
- defines "standard" notification message(s) (to be defined in originator-published WSDL) and generic extensible format for "results" part of notification 
- deals with uncorrelated notification and request with multiple responses (here it's more about correlation scope)
- and optionally (these require stateful implementation):
-- defines monitoring support
-- defines service lifecycle management (i.e. instantiation, state/props change, termination, post-completion results query, etc.)
-- "completed" notification without attached results (both as a WS message, and a non-WS HTTP Req with predefined header)
-- ...
I don't think it's possible to solve these problems with a basic SOAP, but I will consult my WS development team for a feedback.
 
Re #4: Why persistent? Is it a requirement? Your definition of "context data" here extends one in the document:

Context data: The XML data sent to initiate the service.

Results data: The XML data created by the successful completion of the service.

...
When reading the document, I concluded that it's about "Request data" and "Response data" as per WS terminology. If the group chooses to keep these terms/concepts, I suggest changing the definitions to avoid confusion.
 
Re #5: It's defined by the logic supported in WS implementation. In our Realtor WS demo the notification is turned off when the client is declared inactive (e.g. purchased the property).
 
Re #6,7,8: All these are implementation specific. Same as #5.
 
Keith, all,
My suggestion is that we seek input from everyone in the group on their view of the scope/direction for the ASAP. The ideal solution would be for each one to come up with the list of items they would like to see included in the spec and post them to the list. Next we can rank them and work on defining the scope according to the rank/priority.
Thanks,
 

Michael Shenfield
Advanced Research Group
RIM
mshenfield@rim.net
905-629-4RIM x4347
____________________
This information is transmitted on a "WITHOUT PREJUDICE" basis. It is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon, this information by persons or entities other than the intended recipient is prohibited. If you received this in error, please contact the sender and delete the material from any computer.


-----Original Message-----
From: Keith Swenson [mailto:KSwenson@fsw.fujitsu.com]
Sent: October 7, 2003 7:35 PM
To: Michael Shenfield; Keith Swenson
Cc: ASAP (E-mail)
Subject: RE: [asap] questions/concerns on initial working draft doc (and scope)

Let me try to refocus this discussion.
 
  1. ASAP does not specify how you implement the web service.  If you wish to use J2EE, you may use whatever technique.  I thought that describing in terms of stateful/stateless would help in understanding the concepts, and to distinguish the various meanings of the word 'asynchronous'.  I didn't mean to imply that this was the actual implementation.  ASAP does not proscribe how this is implemented in the J2EE world, and so I don't want to discuss this here.
  2. I still think "method" in the spec refers to an operation, because it consists of a request message and a response message. The messages are described, in places, as parameters. Please point out in the document where it means something else than this.  I propose that we change "method" to "operation" in the document in order to conform with SOAP terminology.
  3. Let me ask you a question: do you believe that a special protocol is needed for an operation that can not be monitored?  For example, a service that you send a message to, and a while later you get a response from.  No possiblity to change you mind.  No possiblity to monitor status.  Can't you do this is basic SOAP protocol?  Let's discuss if you think differently, but I am going to assume that this is covered by basic SOAP.
  4. The "context data" is persistent data that exists in the service instance.  It can be sent as part of a reqeust (e.g. SetProperties), or as part of a response (e.g. GetProperties).  Furthermore, there are messages that contain the schema of this context data as part of a response from the factory object.
  5. We really should discuss usage scenarios.  You touched upon the realestate example, one of my favorites.  You describe the service as being a recurring query for houses that meet a specific criteria.  The context data includes the query, as well as the result set. (You might implement this any number of ways, but for now lets imagine that we choose this one.)  The client would make a simple SOAP request to start this service, giving both the initial query, as well as the address to send responses to.  Everytime the result set changes, a notification is sent to the client.  It would be really unpleasant if there was no way for the client to turn this off.  When you started the service, you had no idea how long you would be searching.  You in fact might put the serach end data as a context variable.  Later, you can change that end date by using "SetProperties" thereby extending the duration of the search service, or ending it early.  You can also cancel the service by using the "ChangeState" to the closed state (which is the terminal state).
  6. The client of this service need only know the name of the context variable that holds the query (e.g. "query"), and the name of the context variable that holds the results (e.g. "listings").  Probably, the service instance would not allow the client to set the value of "listings".  Attempts to set this would result in an error.  Some services can not allow changing of context variables at any time, so attempts to set any of them would cause an error.  In this sense, the operation "SetProperties" is optional.  It is not really optional, but can be implemented to simply return an error.
  7. If you don't have a client that can receive notifications, then you also can simply pick up the latest value of "listings" at any point in time.  In this case you would not register an observer address.  Also, you would never receive a completed message.
  8. Finally, others interested in the same listings (the same query) could register to receive notifications of when the listings change.  Note: you are not registering to a specific query, because the query could be change.  Instead you are registering to a specific instance of the service.
 
Now, can we start over with the questions because I am having a hard time deraveling them from the discussion below.
 
-Keith
-----Original Message-----
From: Michael Shenfield [mailto:mshenfield@rim.net]
Sent: Tuesday, October 07, 2003 12:26 PM
To: Keith Swenson
Cc: ASAP (E-mail)
Subject: RE: [asap] questions/concerns on initial working draft doc (and scope)

Keith,
I went back to EJB spec to validate my point on stateless (vs. stateful) session beans. The following is from an EJB 2.1 final draft (section 1.2. What is New in EJB 2.1):
"We have added support for web services. We have added the ability for a stateless session bean to implement a web service endpoint. We have added support to allow all enterprise beans to utilize external web services."
In the current J2EE/Java world only servlets and STATELESS session beans could implement a Web Service endpoint. Neither can support the protocol described in a current working draft (actually it's not true, one can come up with a model when the state is shared by servlet instances using a ServletContext object. It could be a sneaky way to implement monitoring but very inefficient and non scalable one) 
Cheers,
 
MS
-----Original Message-----
From: Michael Shenfield
Sent: October 7, 2003 2:42 PM
To: Keith Swenson; ASAP (E-mail)
Subject: RE: [asap] questions/concerns on initial working draft doc (and scope)

Keith,
My comments/answers are embedded in the orig. message. I suggested at the last conference call that we define the scope of ASAP to clarify what this spec is going to be about. It looks like we have different views on what it should cover.
Thanks,
 
Michael Shenfield
Advanced Research Group
RIM
mshenfield@rim.net
905-629-4RIM x4347
____________________
This information is transmitted on a "WITHOUT PREJUDICE" basis. It is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon, this information by persons or entities other than the intended recipient is prohibited. If you received this in error, please contact the sender and delete the material from any computer.
-----Original Message-----
From: Keith Swenson [mailto:KSwenson@fsw.fujitsu.com]
Sent: October 7, 2003 1:37 PM
To: Michael Shenfield; ASAP (E-mail)
Subject: RE: [asap] questions/concerns on initial working draft doc (and scope)

The whole point about ASAP is to set up a 'contract' to have something done and to be able to check on its progress. [Michael Shenfield] Re: "be able to check on its progress": Then the name is misleading. The spec should either be limited to dealing with async Web Services that support monitoring (I see it as a small fraction) or to make monitoring optional. From the wireless standpoint perspective monitoring is a waste of valuable resources, for the "wired" client it could be useful but requires much more complex implementation of a Web Service. As already pointed out, the scalability will take a major hit as Web Service instance cannot be stateless anymore. 
Perhaps more important is the ability to change your mind and cancel it. [Michael Shenfield] Again, it's up to the group, but I don't think of it as a solid requirement. These are all things that need a "correlation" id of some sort.  What ASAP oes it provide a simple way to request something to be done and receive a correlation id that can be used to check onthe progress.

There are many use cases that fit this model, but there are also many that do not.  A "stateless session bean" is a pattern that ASAP is not designed to support.  Instead, ASAP is designed for the "stateful session bean" where you have a unique instance with an ID, and subsequent requests go back to that same instance.  This session bean is endowed with a goal, and it is expected to last until that goal is accomplished, and then a little while after that (see the timeout setting).  The goal could be "search four house listings for 3 months" or something abstract like that.  [Michael Shenfield] The general agreement in a Web Services J2EE world is that Web Services should only be exposed by servlets or STATELESS session beans - there're tons of references on the topic. I am not aware of any implementations of Java Web Services running as stateful session beans (reasons: scalability, thread safety, management/sharing issues, etc.)

For many implementations of ASAP, the factory will be like a stateless session bean in that it is a web service that simply "exists" and the starting and stopping of it is invisible to the outside world.  The "service instances" then have a lifecycle that can be externally monitored.[Michael Shenfield]  I don't have any problems with a COMesque "CreateInstanceRq", I've used it for years in COM, as well as Home interfaces' "ejbCreate" in EJB. I just don't see Web Services following the same pattern, being involved in many Web Services activities I haven't seen many that mandate user managed instance creation. The other reasons are as per previous comments.

The concept of "fire and forget" (uncorrelated messages)[Michael Shenfield]  "fire and forget" mode is a user experience term. The message request and response(s) share same correlation ID.

 is probably not what ASAP is designed to support.  This would be a single call that later returns a result (or multiple results).  This seems like it can be handled sufficiently with (reliable) asynchronous messaging.  In this case you do not need a correlation id, because there is no other communications with the instance.  As you point out, these do not need monitoring or other support.  Lets discuss this.

As for the concept of "multiple async responses", this is quite definitely what ASAP is designed for.  There is no reason that ASAP is restricted to a single response at the end.  Once the correlation key is set up, the services on both sides can make further requests to each other.  The simplest way to implement this is every new result causes a change notification event back to the observer.  The event might (or might not) carry the new data.  If the event does not carry the data, the observer can do a "GetProperties" in order to fetch the changed data.  The former implementation is most likely to work with a generic ASAP implementation, but people are alowed to extend the ASAP protocol to include special methods, e.g. "NewSearchResult".  In this case the ASAP sets up the basic instance which represents the agreement between the client and realtor, and then the services can inspect the interfaces supported, and if they both understand this extended command, they use it.

Use of ASAP in the above example would allow the client to modify the type of house they are looking for (after receiving a bunch of uninteresting results) or terminate the search (in case they find their dream house).[Michael Shenfield] see comment #2 

Terminology is always a big problem.  We used to call them "interfaces" and now we call the "port types".  I think that our usage of "method" should be "operation" now, right? [Michael Shenfield] No, method in your definition means "message". Operation is defined as a set of Requset, Response, and Notification messages  
If you see things like this that obvisouly deviate from the SOAP norm, please bring these up.  Our goal is to be consistent.  "Context data" & "result data" on the other hand is a concept unique to ASAP for which there is no other term (unless I have missed something).  [Michael Shenfield] Web Service operations are defined using Request and Response (if any) messages. I think "Request data" and "Response data" if you want to define parts (or group of parts) will be more consistent.
 

These are parts of messages, but the key is that these structures persist in the service instance, and can be queried and (in some cases modified) by later operations.

BTW: We are designing Wf-XML as an extension of ASAP, and in that the Factories themselves can be created and started.  This maps into the BPM ability to define and start new business processes.  ASAP is extended to add the new methods for the 'factory lifecycle'.

-Keith Swenson
kswenson@fsw.fujitsu.com
(408) 456-7667

-----Original Message-----
From: Michael Shenfield [mailto:mshenfield@rim.net]
Sent: Tuesday, October 07, 2003 9:45 AM
To: ASAP (E-mail)
Subject: [asap] questions/concerns on initial working draft doc (and
scope)


Hi all,
At the last conference call we had a discussion on taking the initial working draft to the general public. I suggested 'no' based on my initial impression from scanning through the document 2 weeks ago. Finally, past weekend I was able to review the document in detail. Here's the list of questions and/or concerns that I would like to post here for your review:

- Factory "resource".
I am not sure about the concept of "factory" and passing observerURI as a part of CreateInstanceRq. Let's take Java Web Services as an example. When a Web Service deployed as a servlet the hosting Web Server container plays the role of the "factory" but this is "invisible" for the caller. The caller posts to the WS endpoint URI an HTTP request that contains the SOAP message to be invoked. Lifecycle management of the servlet (as a WS instance) is not covered by invocation protocol and therefore "creation" of the WS instance is non of the caller's concern. Similar model stands for the Web Services deployed as stateless session beans, the EJB container hides the creation process. For all async Web Services deployed at RIM (to support application initiated push to a wireless device) we have an "observer" URI (or rather requestor endpoint) passed as a part of the Web Service message. The requestor URI could also be submitted at registration (optionally with a correlationID), so that all following correlated and uncorrelated notifications could be posted to the requestor endpoint. This opens the stage for the next question:

- Multiple async responses for a single request or uncorrelated notification messages.
One of the possible deployments for async Web Services is when a single request causes a number of responses. As an example, one of our demo Web Services "Realtor" uses this model to send listings to a real estate agent registering a new client. The model is obviously asynchronous as we don't want our real estate clients wait (and pay for the airtime) till the request is processed. The "client registration" message is a request that carries the client search information, requestor endpoint URI and generated correlator ID to be used for responses. The server is doing the search in MLS and asynchronously sends found listings each in a separate SOAP message (here we have multiple responses for a single req). Moreover, when a new listing is posted to MLS the server is searching for interested clients and sends the listing to their agents as a notification (correlated notification model). Additionally, the Web Service is capable of sending uncorrelated notifications. We implement the following model: when real estate agent is logging in, the Realtor Web Service gets endpoint URI of the service proxy (linked with the device) and when a new information for the agent is available in the server (e.g. viewing appointment), the Web Service sends uncorrelated notification to the endpoint URI. In my opinion both models (multiple async responses and uncorrelated notification) should be included in the scope of ASAP

- Monitoring support.
In the document there is a lot of discussion on monitoring the execution process and changing the state/properties during execution. I am not sure if this should be mandatory for compliance, one can perfectly deploy the async Web Service without support for monitoring or state change (see example above). Moreover, as an implementer I am not clear on how to implement this monitoring and state altering model in a scalable Web Service - in my opinion it contradicts basic scalability considerations of J2EE or .NET deployment. I think that ChangeState, GetProperties, SetProperties, and StateChange msgs should be changed to optional. As for Subscribe, Unsubscribe, and Completed, I am looking forward to the discussion on how it should be defined in the ASAP context.

Introducing monitoring of the execution is identical to polling for the completion/result and kills async efficiency. I understand the async paradigm as the model where requestor "calls and forgets". The implementation (and ASAP spec) should guarantee that the requestor gets the results (or notified on completion) when ready. Am I missing something here?

- Introduction Section. Language and terminology.
It looks like the verbage of section 1 intentionally deviates from the standard Web Services terminology and definitions. Is there a reason for this? Why should we call SOAP messages as "methods", Request data as "Context data", Response Data as "Results data", etc. Again, I might be mistaken here but my impression was that ASAP is strictly about Web Services?

Sorry to send this 20 mins prior to the conference call, but as I didn't see posted agenda we can as well discuss these points.

Cheers,

Michael Shenfield
Advanced Research Group
RIM
mshenfield@rim.net
905-629-4RIM x4347
____________________
This information is transmitted on a "WITHOUT PREJUDICE" basis. It is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon, this information by persons or entities other than the intended recipient is prohibited. If you received this in error, please contact the sender and delete the material from any computer.



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